Ideas on overheating??

[Lazy Daze]

Raw water is not pulled through the outdrive by the engine mounted water pump. There is a lower unit water pump that is basically an impeller. This pump pushes lake water up through the outdrive and the engine mounted pump simply circulates it throughout the block. They are supposed to be replaced every 2 years.

Raeo, on his boat he does have an engine-mounted, raw water pump (impeller). There is no impeller in the drive. The raw water pump is different than the circulating pump.

Stroh... that's too bad you didn't have the 6 hoses on the housing as there may have been an easy solution. Oh well, moot point.

When it's overheating, can you feel the top of the elbows and see if one side is worse than the other? It's normal for there to be a minor difference, but you should (under normal circumstances) be able to keep your hand on the top of the elbow.

Have you pulled the elbows/risers to check the passages?

Did you closely examine the inside of the t-stat housing, looking for any obstructions?

While the engine is running, remove the small hoses from the water distribution manifold one at a time. You should get clear water draining from each. These are the ones that come from the block drains.

 

[Stroh]

Dennis,

I have shot the exhaust manifolds, risers and elbows with my IR thermometer and the starboard side is a little warmer, within like 10 degrees of the port side. I can easily rest my hands on both elbows after the engine has been running for 5 minutes.

With engine running after 5 minutes or so, I am measuring about 177 at the thermostat housing (180 is about as hot as I let it get) I am seeing about 90 degrees on the two hoses coming from the water distribution housing (Tee'd off) going to the exhaust risers, 140 degrees on the two hoses coming off the thermostat housing going to the bottom of the exhaust manifolds. About 154 degrees on the big hose at the thermostat housing. Roughly 180 degrees at the ends of both exhaust manifolds and about 200 degrees in the middle where both exhaust ports for 4&6 and 3&5 cylinders exhaust into manifold and about 160 degrees on the risers (6" risers), risers are about 140 degrees and elbows are about 90 degrees.

As I said in earlier post, I had removed the port side exhaust manifold, riser and elbow. All looked extremely good, in my opinion. I poked around and even took out the pipe plugs in the various spots and again nothing but normal, light build up. As I said I was amazed how good the inside looked for an 11 year old boat, but again, I have always flushed the engine & outdrive after every outing with "Salt Away". I have not disassembled the starboard side, yet.

Today I removed various hoses. Every one seems clear. I have blown through them and water seems to be flowing all through the places it is supposed to without any obstruction. I again checked water flow coming out of the power steering cooler and again within about 15 seconds I had a 5 gallon bucket almost to the top. I took off both hoses at the risers and ran engine for like 4-5 seconds and water came out like out of a hose from a house spigot.

Inside of the thermostat housing is very good shape as I have had it off several times and pulled every plug and sensor to scrape and clean it well. Almost impossible to pull the two hoses branched off from the hose coming up from the water distribution housing as thee isn't a lot of room in the engine compartment of a 240DA and I don't want to risk getting tangled up in the serpentine belt. I did pull them off today with engine off and checked for obstructions in both hoses attached to the Y-fitting (with check balls in them) at bottom of exhaust manifold on both sides and water came out clear from both hoses.

Tomorrow I am going to remove the fitting at the transom and hook up a garden hose to the hose going to the raw water pump and see what I get, since I have had everything apart but the outdrive where the water comes in and the other end of the transom hose. I'll be surprised if it isn't corroded like the engine side of the transom hose was. I think that will tell me which side of the transom the problem is. Either the problem is in the outdrive or it is possible a restriction somewhere in the engine block. Although based on what I see so far neither of those seem probable, but the outdrive side seems a better chance.

It just acts to me like the hot water is not getting out of the engine like it should, which leads me think flow speed or volume is either too fast/to much or too slow/not enough. Originally, a while back, I tried running without the thermostat and it made no difference. I may try that again just to see if anything changes.

Thanks again.

 

[scoflaw]

Water in....water out......all the water exits the manifolds, risors, elbows. Stupid/simple system.

 

[Lazy Daze]

I mistyped about the small hoses at the distribution housing. You don't need to remove them while the engine is running. In fact, you don't even have to have the engine running. Just pull them off and see that water drains well from them. Those hoses are quite small and are a common place for sand/silt to start to collect and back-up into the block.

I can't imagine you have any issues with a water supply issue. With the test you did, you are getting PLENTY of water into the engine. That eliminates the entire supply side from the list of variables.

Honestly, I never really use an IR gun but most of those numbers sound fine, with the t-stat one just being a bit high. However, I wouldn't be surprised by certain areas of the housing being higher. BUT, since you can comfortably keep your hands on the risers (and that 10-ish degree difference sounds about right), it really doesn't sound like you any exhaust issues, either.

The only other thing I can think of is that since you don't have the "balance flow" setup in the t-stat housing, I believe there is a different setup and it involves a ?nylon? ball in a fitting under each manifold. I'm not positive, but I believe this is a "new design" balance flow setup. If one/both of those are sticking at idle flow speeds, then the advanced throttle setting clear it up... That is the EXACT symptom that the "T" in the t-stat housing would cause when it gets old. The quick remedy is to stretch out the spring. In your case, though, I do not believe there is a spring involved. But I would pull that fitting out and inspect things. Hopefully you find something obviously wrong. If not, I hate to replace things without being sure, but I might do that in this case and, worst case, chalk it up to "it's good PM, anyways".

You mentioned your impeller end plate is slightly scored. I would normally expect that to cause issues at higher speeds, but just to rule it out... Do the water flow test at idle speed. I don't know of any spec from Merc for idle speed, but let's see what the difference is at idle, compared to 1,000RPM. If it's still anywhere CLOSE to the Merc spec for 1,000 (which is roughly 2 gallons in 15 seconds) then I highly doubt the raw water pump is the issue. Again, just trying to rule out variables. But I'm really leaning towards something being amiss with those balls.

 

[romanservices]

you are running this on a hose right? so basically you are forcing water into the system rather than letting the raw water pump suck it up. put your drive in a bucket if you can then run your flow test. naturally when you are in the water traveling you are again forcing water into the pickup. I think even just idling up will increase suction and pull in more water to cool it down. On the brass version the cover plate is the wear plate. There are rebuild kits out there that are basically a 16g stainless steel plate that fits in there.

I'm sticking with it being the raw water pump... I'm just stubborn

 

[Stroh]

No, I am not running on a hose. Boat is kept on a lift and I am dropping it in the water to run. In fact, this evening, I took it out and idled around the large canal I live on at about 1,000 rpm and the temperature slowly went up until it hit 195 degrees and the alarm went off. As has been standard procedure I put it in neutral and rev it to about 1500 rpm and after a minute the temperature slowly comes down. This is exactly the same conditions that started me on this quest. I'm no Smokey Yunick, but I have been a motor head all of my life and after seeing what the old impeller looked like (it was like new after 200 or so hours) and then completely rebuilding the raw water pump and seeing the output from the boat sitting in the water (not from a hose), I just can't believe that pump is the culprit.

Dennis, as I said in previous post, I pulled both hoses off of those fittings on the bottom of the exhaust manifolds with the check balls in them and the water ran clear, no sand at all came out. I checked operation of the check balls and they are free and seem to seal pretty well, when they seat, just drip a little.

I am feeling more like it is probably the outdrive end of that hose that goes through the transom (Bravoitis). I am checking flow for only 15 seconds after engine has been cold. Maybe after running and gaining temperature, flow decreases enough to throw the balance of flow through the engine out and allows the temperature to climb. I am going to try to hook up a hose directly to the raw water pump intake hose and eliminate the water intake system through the outdrive and see what difference if any that makes.

Thanks again all.

 

[Lazy Daze]

Stroh, as I mentioned above, the two little hoses I am referring to are the ones on the water distribution manifold. These are, essentially, your block drains. If those run clear, you know (most likely, anyways) that the block is relatively clear of sand. Draining from the manual drain point will not necessarily show this.

I'll be very surprised if there is any issue with the "flow path" of water from the drive. Meaning, I'll be surprised if there is any blockage there causing any issue. The amount of water you're getting in your flow test is so high, I just can't imagine that being the problem. Especially since you said you checked the "bravoitis" area out and cleaned it.

It's been so long since I've seen those check balls (and don't have one on the shelf to look at since it's such a low priority item)... Are they solid? If hollow, could they have a hole in them that allows water in them, thereby possibly affecting the operation once everything is all sealed up?

Just as a side note... installing a thru-hull for the water intake (as opposed to thru the drive) is generally considered better than OEM.

 

[Stroh]

Dennis, I have been trying to load a picture earlier and just now a parts diagram of my cooling system (hoses, etc.) and no matter how small I make the jpeg file it won't upload.

Anyway, the only water distribution "housing" on my engine is a plastic ball type thing on the port side lower front of the engine. It has three hoses and a drain (my engine has the "single point drain" configuration). One hose from the raw water pump (supply), one going to the water pump (through the oil cooler tube) and one going up the port side front of the engine to a tee and the two hoses going off of it go to the risers. On the bottom of the exhaust manifolds there is a fitting (metal half of it is in the manifold and lower plastic half) that has two hoses and inside is a check ball. I don't see any block drains with hoses on them. In fact, I never noticed any block drains at all come to think of it. I will check that out tomorrow.

As far as installing the thru-hull for raw water intake, what is done about cooling water for the Bravo 3 outdrive? Doesn't it need the incoming water flow to cool it or will just the water flow out the exhaust keep it cool enough and so you just cap off that pesky transom hose hole? Because I know for a fact that hole is below the waterline. Thanks for bearing with me.

 

[Stroh]

Here is a link to a parts diagram that is 98% right for my cooling system:

http://www.mercruiserparts.com/bam/subassembly/31851/11681/250

 

[Lazy Daze]

Thanks for bearing with me.

No worries, I'm a boater, too! I know how frustrating these types of things can be when it seems like you're chasing a gremlin.

Look at #9, that's the water distribution manifold I'm referring to. There are (2) #10's. Those are your block drains. While these may not be the issue, it's easy enough to check them out and rule them out. It's also good to know about these for winterizing time. If they got blocked up, and someone only drained the system through the blue handle, it wouldn't necessarily drain the whole block... but they would see water coming out the orange tube and assume that everything is draining.

 

[Lazy Daze]

As far as installing the thru-hull for raw water intake, what is done about cooling water for the Bravo 3 outdrive? Doesn't it need the incoming water flow to cool it or will just the water flow out the exhaust keep it cool enough and so you just cap off that pesky transom hose hole? Because I know for a fact that hole is below the waterline. Thanks for bearing with me.

You simply cut the cooling hose on the drive side of the transom and leave it open. As the boat moves forward, water will be forced into the intake and up through/out the hose (the open end is still on the outside of the transom) for a constant supply of water going through.

EDIT: Oh, by the way, there is a new hose/plastic fitting design fitting design from Merc that is "supposed" to cure bravoitis. We'll see... time will tell. :smt101

 

[Thornton69]

You simply cut the cooling hose on the drive side of the transom and leave it open. As the boat moves forward, water will be forced into the intake and up through/out the hose (the open end is still on the outside of the transom) for a constant supply of water going through.

EDIT: Oh, by the way, there is a new hose/plastic fitting design fitting design from Merc that is "supposed" to cure bravoitis. We'll see... time will tell. :smt101

When the hull is on step, that cut hose will be above the water line. I don't think it would it would be a good idea to leave it open. Plugging it would be assuming you also have a through hull intake. My SR has both options. Ball valve installed on the through hull.

 

[Thornton69]

The diagram you posted looks more "stupid" complicated than simple. Wonder if it is possible that the first pump cannot keep up to the second? Would this not allow the overheated water to recirculate back to the engine when the thermostat opens? Higher rpm with no load may be replenishing just enough to make the difference. I have never needed to open my through hull with my Bravo, but I also have fresh water cooling. If you are confident the intake is not restricted then would have to agree with previous posters to revisit the raw water (first) pump.

 

[pineknollj]

my boat is a 2005 320 twin 350's raw water cooled via thru hull. I have owned her since March 07.

port motor was overheating sometimes at idle but for sure just after going on plane. all parts checked out on hoses, pumps thermostat circulating pump. exhaust manifolds were replaced January 2013. could not believe they could be the issue. we removed and hooked a house to intake side and turned on water full blast (city water pressure very good). water just trickled out versus gushing out. manifold was the culprit. first time it failed in 3 years. replaced manifolds risers elbows and no more issues with overheating. I had replaced the seawater pump thermostat serpentine belt too. old thermostat checked good too but replaced too. check ball was operating correctly. it was the manifolds.

Sent from my SM-G920V using Tapatalk

 

[scoflaw]

This how you trouble shoot this issue. You have plenty of volume from the pump, so forget about raw water pump and adding thru hulls, it's not your problem. Obviously water is coming in but it's not getting out.

Get your boat on your trailer and put the water muffs on in your driveway. Hows the flow exiting the stern ? Then start working your way forward. Take off those big rubber couplers that attach to your elbows. Is the flow better ? This will tell you if you have an obstruction in your Y pipe or leg. Now take off the feed lines to the manifolds and check volume there. Keep working forward until you find your restriction

 

[Lazy Daze]

When the hull is on step, that cut hose will be above the water line. I don't think it would it would be a good idea to leave it open. Plugging it would be assuming you also have a through hull intake. My SR has both options. Ball valve installed on the through hull.

Thornton, the purpose of cutting the hose (and leaving it open) is so that water flows through the drive to help cool it. It it was plugged, there would be no flow.

A "T" on the inside of the boat to receive water from either the drive or a thru-hull is certainly another way of doing things. I'm wondering, though, what any long term possible effects may be since there is still, essentially, a water path going through the drive/transom. Whereas with a block-off plate, it totally eliminates that. Granted, a "T" is easier/quicker to install.

 

[Thornton69]

Thornton, the purpose of cutting the hose (and leaving it open) is so that water flows through the drive to help cool it. It it was plugged, there would be no flow.

A "T" on the inside of the boat to receive water from either the drive or a thru-hull is certainly another way of doing things. I'm wondering, though, what any long term possible effects may be since there is still, essentially, a water path going through the drive/transom. Whereas with a block-off plate, it totally eliminates that. Granted, a "T" is easier/quicker to install.

Sorry Dennis. Looking back, I am not sure how I interpreted your earlier post to leaving the transom side open. Guess my head was stuck on engine cooling side of it all. Makes clear sense to leave the outdrive side open. Never really thought about the drive side of it so thanks for taking the time to clarify. Enjoy reading yours as well as all other's contributions. Hope mine don't lead anyone astray.

 

[CliffA]

don't forget my post about the water circulating pump.....I think I would try replacing that pump based on your testing so far before I went through the trouble re-engineering the cooling system......as was said earlier it seems like you have plenty of water being drawn into the engine....it appears the water is not being circulated fast enough through the engine and/or not ejected from the engine fast enough to cool the engine......

cliff

 

[Stroh]

Update
So, in order to positively eliminate a water intake problem from the outdrive side of the “Bravoitis” hose, I removed the hose off of the only thru-hull I have, (my A/C unit water intake) and ran a hose from the transom fitting (intake) to the thru-hull so I could pull water from it. I lowered the lift and put the boatin the water, ran it and was still overheating.

Next, I followed Dennis’ advice and checked the port side block drain, it flowed clear water just fine. By the way I doubt the cooling system has been regularly drained since it has always lived in non-freezing climate and the only drain point it has is on the water distribution housing where the 3 hoses #11, 17 and 19 (from the diagram I posed the link) attach to it. I also pulled the exhaust elbows off to look at water flow out of the exhaust and it seemed fine from both port and starboard. Remember, I only removed the port manifold, riser and elbow and found them all looking good inside like only running in freshwater for a couple of years, almost no scale or rust buildup.

Next, I bit the bullet (Cliff) and even though I wasn’t convinced the circulating pump was the culprit I bought a new one and replaced it. No change in the overheating problem. I then pulledthe starboard side exhaust elbow pipe to check that flapper, it looked fine just like the port side. Next, I decided to remove the block drain on the starboard side (what a *****!) in getting access to it I decided to remove the 3-way fitting that was in the way. I separated the three hoses #13, # 3 and # 15 (on the diagram) when I got #15 off part of the flange for that hose was broken and stayed inside the hose when it was pulled off the fitting. After I got all of that off I noticed the inside of the hose had some blisters and thought maybe the inside was separating when the water was flowing and after awhile was filling up like a sack and restricting the flow through the hose. So, I ordered the hose and the fitting and went back to pulling out the starboard block drain. Once I got it off I found it was plugged up with black mud. I poked the block hole just a little and the hose hole with a small screwdriver and got plenty of clear water flow out of both.

Since I have a couple of days before receiving the other parts I need to put it back together, I decided to pull the starboard elbow (it was fine, like the port side) the riser (it was fine like the port side) and the exhaust manifold, since I had ordered gaskets for both sides at once. Well, the starboard manifold water jacket was plugged.

There are three holes on the bottom of the manifold, two that have pipe plugs in them and one that has a drain fitting in it that has a check-ball drain with the hose from the raw water pump and the water hose from the thermostat housing going to it. The top of the manifold has two holes where the water goes up into the riser to go out the exhaust.

After getting the manifold off the boat I poured some white distilled vinegar into the top holes and stopped up the two bottom holes with corks from the wine bottles I have drained while working on this problem, filled up the water jackets and let it sit overnight. This morning, I took a flexible wire chucked up in a drill and was able to clear the two outside holes that have pipe plugs in them but couldn’t clear the center hole that has the fitting in it. So, I ran down to Offshore Performance in Ft. Myers and bought a new exhaust manifold.

It will be a few days, while I’m waiting on the other parts, before I can run it again but the plugged manifold is probably the answer.

Because the exhaust manifold is supplied water by one hose and the riser and elbow are supplied water from a different hose I was misled by the water flow out the exhaust and also the fact that the starboard riser was within 10 degrees of the port riser temperature and the exhaust manifold temperatures were close (at least on the outside), from checking with a IR thermometer and only running the engine for no more than 10 minutes. I was also faked out by the fact I could cool it down by revving the engine. I would have thought revving it with no cooling water flowing in the exhaust manifold would not make the temperature go down but go up.The main bad on my part was assuming (we all know what that makes u & me) that because the port side manifold, riser and elbow were good inside that the starboard side would be too.

So, once I get it back together and confirm problem is solved, I will put on my “to do list” to replace the other exhaust manifold, both risers and elbows.I will post what happens in a week or so.

Thanks once more for all the ideas, input and comments. I hope documenting my tribulations can help someone in the future.

 

[CliffA]

good work...sounds like you found the problem.....none of us like to throw parts at a problem but sometimes when the root cause isn't obvious we don't have a choice......at least when you are finished you will have full confidence in the cooling system because all the components have been tested and most are now new......

good lesson for all of us that do our own maintenance....don't ever 'assume' something connected to the problem you are working on is in good working order....

cliff