another mercruiser overheating!!

[steve930]

hi guys. I joined the forum a while back, I'm based in england & bought a 1990 220da a couple of years ago, i've mainly been reading posts on here what a great forum you've all created.

This post will be long winded with some vids, so please bear with me

The boat had a new 350 engine fitted in 2007 along with new manifolds/risers and only did a few hours running. The previous owner then had major health problems which resulted in the boat being unused/sat in dry dock until august 2010 (when i bought the boat). I got the boat running/took her to my port & used her for the rest of the season. Whilst cruising at upto 3500rpm she would run at 165-170 F, if you increased revs beyond that the temp would rise to 220! . I planned over the winter to pull the boat and do a whole load of refurb work ready for 2011 season.

WORK DONE:

leg serviced with new raw water pump/pipe/pipe to steering cooler
exhaust flappers present & correct
inlet manifold removed, water galleries all look clear (converted eng to efi)
engine high pressure steam cleaned through all waterways
thermostat replaced
circ pump inspected wi thsnap-on mini cam (looks ok)

I still have the same problem! If you push revs beyond 3500rpm the temp will climb to 220f within 2-4 minutes, backing off to 1500rpm the temp will drop to 145f within 20 seconds

Below are some vids i shot tonight of waterflow from the leg, see what you guys think??

Thank you

There are 4 videos on the top row of my album with the first on the far right & working left!

[video]http://s195.photobucket.com/albums/z253/steve930/?action=view&current=video-2012-09-13-17-48-51.mp4[/video]

 

[AKBASSKING]

Well the system only has a few componets.

Raw water side check the following:

Raw water sea strainer
Raw water pump
transmission cooler
heat exchanger (if closed system)
Risers

Closed system check in addition to above:

Heat exchanger
water pump
thermostat

After all this then you may have an engine block issue

 

[njmello]

Even new risers wil scale up and restrict flow real quick if it was run in salt water, put away wet and then stored for 3 years.

 

[kkalsch]

I had the same problem about 10 years ago on a Alpha drive-one of the blades on the impeller broke off and was stuck in the tube that goes from the impeller housing up into the top of the stern drive -took awhile to find it -I finally figured out that's why the guy sold the boat-So if you take the drive off to check the pump again ......check the tube

 

[Lazy Daze]

Pull the water inlet hose off the t-stat housing and run the engine. Dump the hose into a 5-gallon bucket for exactly 30 seconds and see much how water you get in that time. The engine will be fine - it won't overheat in this short time period. Let's see how much water is making it's way to the engine - this will at least help to narrow down where to look.

Will you be running the boat in the water or off a hose for this test?

EDIT: Wait - I just saw that you have videos - sorry, missed that part. I'll take a look at those.

 

[CliffA]

make sure the drive belt is tight against the water circulating pump and you may want to replace the belt, especially if it is glazed from slipping in the past...if it is loose or cannot get a good grip on the pump pulley the belt could slip and not turn the pump fast enough at higher RPM's to circulate enough cooling water....sometimes just a visual inspection of the circulating pump will not indicate if it is working properly or not....your symptoms sound a lot like what I was experiencing when i first got my boat...after i replaced the thermostat and circulating pump the temps stayed 160 - 170*F at all speeds.....

good luck...

cliff

 

[davefin]

I would also recommend getting a laser thermometer and shoot the area at the temp sensor when the gauge is reading 220. This may tell you that the gauge and/or wiring to the gauge is faulty.

 

[CliffA]

I would also recommend getting a laser thermometer and shoot the area at the temp sensor when the gauge is reading 220. This may tell you that the gauge and/or wiring to the gauge is faulty.

for what's its worth, i recently used a laser thermometer to check the heat readings on the engine while using a garden hose for water supply.....after warming up to normal operating temp at around 160* on the gauge i checked the temp of the exhaust elbows and thermostat housing....the port exhaust elbow showed a temp of around 110* and the starboard elbow showed a temp of around 135*....the thermostat housing temp was around 110*.....maybe this is a normal variation between the gauge reading and the laser temp reading, but it seems excessive to me.....i would have thought the temp readings would have been closer together...

cliff

 

[Lazy Daze]

OK, disregard the test I mentioned above. It appears you have good water flow coming to the engine so you can rule out the outdrive... BUT, just to double check, do the same test you did (coming off the cooler), but this time rev up the engine to verify water flow increases with revs.

IR gun is a fantastic tool and that would certainly help to see if you have a "real" overheat, or just what appears to be an overheat. Another easy way to check for "real" vs "fake" is to put your hands on the top of the risers. If you can keep them there, the engine is doing OK. They should be warm, but not too hot that you have to remove your hands. Note, that it is common to feel a slight difference in temp from one riser to the other.

OK, here's something that often slips through the cracks, but can absolutely cause what you are seeing... Are you sure the t-stat is in correctly? When looking at the housing upside down, it should go: Housing, t-stat gasket, t-stat (point down), plastic spacer, housing gasket. Also, be sure not to use any type of grease on the housing gasket's contacts.

 

[steve930]

hey guys, thanks for all the advice & pointers so far

the engine has new drive belts (tensioned correctly)
i've had exact same problems with old & new raw water pumps and lazy dave believes i have good water flow at idle speed at least
I will double check points on engine with a temp gun

@lazy dave

I will re-check water flow from leg with more revs but as you say water flow is good at idle which is what i wanted confirmation on
When i converted engine to EFI i had laptop hooked upto OBD socket just to check all parameters & give or take a few degrees the engine ECU was seeing the same temp readings as whats displayed on the dash gauge. I will try & take boat to sea this weekend with the laptop connected to engine just to double confirm.

If all of the above checks out then i'll double check thermostat/gaskets, I do remember that the stat housing was quite rusty, otherwise i'm thinking maybe the risers , as i never separated them from the manifolds when i did refurb work (i don't know their condition)

 

[steve930]

aaa

 

[steve930]

OK, disregard the test I mentioned above. It appears you have good water flow coming to the engine so you can rule out the outdrive... BUT, just to double check, do the same test you did (coming off the cooler), but this time rev up the engine to verify water flow increases with revs.

hi Dave

I did the water test again whilst revving the engine, check out the video below. I revved the engine to approx 2500rpm.

When i originally had the laptop hooked upto the boat's obd we were using my bro's laptop etc (we're not talking at the min!!) I hooked up my laptop using my elm327 odb2 interface hooked upto a obd2 - obd1 coupler, but it won't communicate. I think i need to get a dedicated obd1 interface??

I do remember when i last changed the thermostat that the housing was in poor condition, so if your happy with waterflow from the leg then i'm gonna changed the thermostat & thermostat housing together, thanks for the heads up about how the stat sits

[video=youtube_share;i9S2slzvvbE]http://youtu.be/i9S2slzvvbE[/video]

cheers steve.

 

[Lazy Daze]

Steve, it was a little hard to tell how much water was coming out, due the angle of the camera and then the extra water back feeding and sloshing around the cockpit. But, from what I could tell, it looked like very good flow and also that it increased nicely with revs. If you were seeing the same thing, in person, I think it's safe to say that you have a good water supply.

Don't condem the housing based on the interior looking ugly. That iron is quite thick and it's rather rare for a housing to be a problem. It's normal for it to have a VERY rough interior. As long as the passages are clear and the area where the t-stat sits is relatively even, I'd say save your money.

By chance are you out of the water? How does the water flow look where it exits those two holes in the outer transom plate? My only thought here is that if there is a blockage AFTER the t-stat housing, you wouldn't get good flow THROUGH the engine.

I'm by no means an expert when it comes to ECM's (computers), but if you're running an EFI (not MPI) system, then I believe the computer speaks "MEFI3", not OBD as that is automotive based. I believe Rinda makes a scan tool that would work... But again, double check me on this stuff.

 

[scoflaw]

I would suspect risers are in poor condition and plugged up, not letting the water out of the system.
Since you said you have not inspected them yet, I would start there.
Improper ignition timing can make your motor run hot as well

 

[njmello]

I had the same problem with my 350. Previous owner had the boat unused for several years in the driveway. After running the boat a few times the temp would be 'normal' until run at higher rpms when the temp would rise. The condition got progressively worse until it would overheat, even at idle. Going through the system, starting at the impeller (which I replaced immediately after getting the boat) - the process became a nightmare. When I checked the (new) impeller, sure enough, one vane had broken off, partially blocking the outflow - fixed the problem, right?

Wrong! Discovered a leak in the outdrive to transom hose on the outdrive side. Patched that and the hose started leaking on the transom side. Impossible to fix without removing the gimbal housing.

Brand new 'problem' = gimbal pin splines are stripped - can't remove the gimbal pins. Had to drill them out. Luckily I have a friend with a machine shop that 'restored' the threads (discovered that someone had used locktite on the ENTIRE 1" of gimbal pin threads). Did a complete gimbal housing 'restore' - new bellows, hose, bearing, etc. Problem fixed, right!

Wrong! I'm now getting the required 4 gals a minute from the sea pump - same problem, overheating at idle. Discovered the circulating pump was the automotive version. Was working, but could see (after removing the backing plate) it wouldn't be long before the steel plate would pit through and start leaking - replaced the pump with the marine version. Also found the T-stat was the automotive version (160 degree) - replaced that with the marine 142 degree. Since I had it apart, I removed the T-block and sure enough the 'bypass' was scaled up restricting flow to the circulating pump. Put it all back together, fixed the problem, right?

Wrong again! Same problem. Removed the logs w/risers. Removed the end plates - logs OK. Seperated the risers and sure enough. Scale had blocked the raw water exits and the steam holes were plugged as well, no way for the circulating water to escape. Replaced the risers with new, put it all back together - problem fixed FINALLY, right?

STILL WRONG!!! Now I'm absolutely nuts. Ready to put a bullet in the engine. Walked away before that happened, to reassess. Back to square one, start over. Back to the impeller. Dropped the bottom half of the outdrive and sure enough, the impeller (and body) were trash. Apparently, with no means for the water to escape through the risers, the water in the impeller and body got hot enough to screw up the body and blades, Replaced the impeller and body and . . . .

FINALLY!!! SUCESS!!!

FYI - according to my 'tech' mechanic the 350 requires 4 gals a minute at 1,000 rpm. Like the earlier post said - disconnect the fresh water supply hose at the T-block - stick it in a bucket, start and run the engine for 15 secs and turn it off. Pour the water in the bucket into an old 1 gal milk jug. The water from the bucket should fill the jug. If it's 'short' the problem is before the water gets to the engine.

There is a 'bypass' in the T-block that allows fresh (cool water) to the circulating pump which can clog with rust scale, restricting the flow - make sure that has no blockage. If it is clear then the next likely blockage will be in the risers. Be aware there is a small (steam escape) hole between the log and the riser that will clog. Steam generated in the log is supposed to 'escape' into the riser (if no steam generated water flow through the hole is negligible). Steam in the cooling system will tend to drive the temp up at higher rpm.

The 'clue' is "sitting" for 3 years if it was put away 'wet'. The risers and logs should be drained (there are plugs for that purpose in both logs and risers) if the engine is to be 'stored' for any length of time. I always drain my logs, risers and engine (which also has plugs for the purpose on both sides) for 'off season' layups. My engine already has petcocks for draining the water jacket and I intend (next layup) to replace the log and riser plugs with petcocks as well.

Hope this info helps.

 

[steve930]

Hi dave, thanks for taking the time out to reply. I'm happy there is sufficient water supply from the leg. I forgot to mention that i'm not running mercruiser EFI, I built up a TBI system using components from a chevrolet suburban & a camaro which is running on a suburban ECM which has had the prom re-flashed for marine purposes (my brother specializes in corvettes over here in England and has other american vehicles pass through his workshop from time to time) So yes the system has obd1 for diagnostics.

When i last changed the thermostat i noticed a waterway (see pic below) which i;ve marked with a red line, Now if its mean't to be there then the hole is only about 10mm in size & obviously if its not mean't to be there then i may have a problem plus the underside of the body is i think on the verge of leaking

The boat is still in the water at present, so i can't check waterflow on the exhaust. I normally keep the boat in water until december then i pull her out on a trailer until march/april time

Thanks scoflaw & njmello. If the thermostat housing is a dead end then risers are next on my list, but if this is the case i may put off stripping these down until december when i pull the boat back out of the water,

FWIW the previous owner had the boat on a dry stack & each time the boatyard pull a boat they flush the engine with fresh water before it gets put back on it's shelf

Thanks again guys for all the help

 

[Lazy Daze]

I like your ingenuity! Making your own TBI, that is! But, I think you need to stay on "speaking terms" with your brother! :smt001

OK, I didn't realize you had that style of t-stat housing (re-used from the old engine?). Inside that metal tube... the one you are pointing to... is there a metal rod, spring and two nylon balls? If so, pull the spring out, stretch it out a bit by hand (make it a little longer), reinsert and see how that does.

That 10mm hole going through that metal tube does seem quite small. Perhaps it's corroded up and clogged. Maybe changing the housing isn't such a bad idea after all. You might consider changing it to a newer style (if the intake manifold will allow it). It would mean possibly eliminating those two upper hoses and maybe changing the intake hose (possibly the other exhaust hoses).

Also, disregard what I mentioned above about how to insert the t-stat - I believe yours inserts from the top, not the bottom? Either way, making sure it's in the proper order is good to do.

Have you had a chance to see how hot the tops of the risers get when your temps start creeping up?

 

[steve930]

hi david.

It was cheaper/easier to build up my own tbi system (in the u.k. ) and i think its basically the same system as mercruiser use. My brother & i have "one of those relationships", six months down the road & all will be good again til the next time:grin:

The passage with the hole i refer to in the stat housing is following the route/direction of the red line in the photo, its not the tube with the spring loaded balls, which are all present and correct. As you suggest i think the housing was re-used from the original engine

I will look into new housings tomorrow, i expect i will order from your end of the the world, as even with carriage/customs duty its much cheaper than buying in the U.K. ! It just means i'll have to wait 7-10 days for it to arrive

I lent my temp gun to a friend & i'm gonna go get it on wednesday, then i can get some readings

cheers, steve.

 

[Lazy Daze]

I'm not familiar with that housing, so I can't answer that question. But, I do wonder if the newer engine/intake manifold requires a newer housing for better flow? That's just a guess, though. All I can think is that there must be a reason that Merc changed the housing design.

Just for giggles, pull that spring out and stretch it out a bit.

Check the temp on the top of the risers with your hand. IR gun is great, but your hand is a wonderful tool for things like this, as well.

 

[steve930]

I have been reading stuff on the net & found some info but I don't know if it's relevant or not:

My boat has had an alpha gen2 leg fitted in place of the original gen1 leg. I found an article stating that the water pumps in the legs have different flow rates & when mercruiser launched gen2 they also changed the stat housing from design #1 to either design #2 or #3, so could this cause a problem or am I barking up the wrong tree here??

So to sum up, I'm running an alpha gen2 leg with a design #1 thermostat housing. As I'm gonna order a new housing I obviously want to get the right one for the job.

If your unsure is there a mercruiser