(Circulation) Water Pump Question

[Bill Goetz]

We have a 1996 300 Sundancer DA with 5.7L V8's. We've been battling high running temps. Runs fine up to 3000 rpm, then climbs past 170 degrees as rpm increases. Also lots of steam from the raw water exhaust.
We've done just about everything we could think of (leak/compression test, test for blown head gasket, cleaned heat exchanger, thermostat, new raw water impellor, etc., etc) Our next stop is the water circulation pump. Valve cover got so hot that it melted the wire loom wrapping around some wiring. So our next stop is the closed water circulation pump.
We can not find a listing for this pump anywhere, even the Mercruiser factory parts site. Every parts diagram I've looked at shows the pump, but its grayed out. Any one have any experience with this?
OH NEVER MIND. IT'S LISTED WITH THE INTAKE MANIFOLD!! SILLY ME!
Any other suggestions still welcome!

 

[PlayDate]

Bill it sounds like there is a raw water restriction. On most engine configurations the outflow of the raw water pump snakes its way to the oil cooler and/or trans cooler first then up to the heat exchanger.

It isn't fun work but you have to pull the outflow hose off at the pump and the cooler. There is a good change you have impeller debris in there that is restricting raw water flow at higher rpms. At low rpms it the debris stays at a low point in the hose. But at higher rpms it moves and blocks water flow at the first cooler it encounters.

 

[dwna1a]

PD is spot on. The busted veins settle in the oil cooler. Take the hose off and look there for any restrictions

 

[Bill Goetz]

Bill it sounds like there is a raw water restriction. On most engine configurations the outflow of the raw water pump snakes its way to the oil cooler and/or trans cooler first then up to the heat exchanger.

It isn't fun work but you have to pull the outflow hose off at the pump and the cooler. There is a good change you have impeller debris in there that is restricting raw water flow at higher rpms. At low rpms it the debris stays at a low point in the hose. But at higher rpms it moves and blocks water flow at the first cooler it encounters.

View attachment 150311

I thought that we addressed this. We pulled the engine last winter and replaced the impellor. Although it was worn, it didn't appear to have any pieces missing. But maybe we missed something. We also pulled all the hoses from the heat exchanger and cleaned the screens as best we could. Yesterday we did the bucket test on the seawater output and both engines seemed fine (about 6 quarts in 15 seconds). Although that's at idle, so all bets are off at cruising speed. We bought the boat last year and it had been sitting for 3 years, so the maintenance history is unknown. I ordered a water pump, just in case, so we'll see where that goes. And while we're in there we can follow your suggestion as well. We're also going to pull the heat exchanger and have it professionally cleaned at a radiator shop.
Update: I've scoured the Mercruiser parts book and I can't find anything related to an oil or transmission cooler. on our engine.

 

[scoflaw]

How old are the exhaust manifolds?

 

[Bill Goetz]

Brand New

 

[PlayDate]

Well.....for fun just follow the hose that leaves the pump (pressure side) and see where it goes. As I mentioned the issue is if there is debris in that hose.......it could be the problem. There are multiple threads this year on exactly this issue.

Check this one out:

http://clubsearay.com/index.php?threads/sea-water-pumping-issue-25k-in-so-far.113338/page-2

 

[Bill Goetz]

ReplyWell, I wish it was that. My partner (my son) pulled all the hoses this winter and pulled one small piece from them. Otherwise everything was clear. The saga continues.

 

[PlayDate]

Okay.....the next likely issue if you are convinced you do not have a blockage is an air leak into the system. Same thread I referenced before.

I have a couple of methods to finding a problem like this. You can replace one of your hoses with a clear vinyl hose and watch for bubbles. Or you can rig up a pressure gauge to see what is happening to the water flow.

I will add a picture of the pressure gauge later today.

 

[dwna1a]

Bill, I think folks are saying that over the years of the boat Pieces of past impellers will get deposited down in the oil cooler. That’s the first stop in the water flow after the pump. Then they suddenly move and will cause a blockage. That is where I found many old pieces.

Im fighting the same issue right now. I wish you luck

 

[Bill Goetz]

Thanks all. We'll do the water pump and see what happens.

 

[PlayDate]

 

[mrsrobinson]

When I was dealing with an overheating issue last season, both engines, I replaced the impellers. The ones I removed were intact. That did not resolve the issue. As I continued to chase the issue down the raw water line I found impeller bits lodged in the heat exchangers. I have no idea where they came from since the ones I pulled out were completely intact, but that ultimately was my issue. I cleaned them out, flushed the exchangers, and the temps came back down to normal.

I like the clear hose suggestion as well, check for bubbles, I now have one of my boat just in case. Shop cut a piece for me and gave it to me.

 

[Goatz]

I will jump in here. I am Bills son. All hoses were removed last year and I looked in the Transmission cooler so I know it is clear, but did take a quick look in it while hanging upside down with a flash light. There was a couple of vains from an old impeller (last year) that I removed so quiet confident that the hoses are clear and transmission cooler is good to go.
We puller the circulation pump the other day and opened it up. I look in great condition and in no way did it seam that the impeller was slipping on the shaft like some have found.
I dropped off the heat exchanger at radiator / heat exchanger place to have it cleaned and inspected. There was some repairs in the past to it, so that may be the issue. Not enough flow or cooling but they said they can test it to see if it is still effective.
So jumping ahead while we wait for the heat exchanger, where would be the best place to insert clear hose to check for air bubbles. The clear hose will colaps so would not think before the raw water (fresh water) pump would be a good idea. So from raw water pump to trans cooler or cooler to heat changer are the only other two. Both are molded hoses so getting the clear hose in place will be a interesting.
Thought?
Thanks for you help!

 

[mrsrobinson]

I will jump in here. I am Bills son. All hoses were removed last year and I looked in the Transmission cooler so I know it is clear, but did take a quick look in it while hanging upside down with a flash light. There was a couple of vains from an old impeller (last year) that I removed so quiet confident that the hoses are clear and transmission cooler is good to go.
We puller the circulation pump the other day and opened it up. I look in great condition and in no way did it seam that the impeller was slipping on the shaft like some have found.
I dropped off the heat exchanger at radiator / heat exchanger place to have it cleaned and inspected. There was some repairs in the past to it, so that may be the issue. Not enough flow or cooling but they said they can test it to see if it is still effective.
So jumping ahead while we wait for the heat exchanger, where would be the best place to insert clear hose to check for air bubbles. The clear hose will colaps so would not think before the raw water (fresh water) pump would be a good idea. So from raw water pump to trans cooler or cooler to heat changer are the only other two. Both are molded hoses so getting the clear hose in place will be a interesting.
Thought?
Thanks for you help!

The clear hose my service shop cut for me is not collapsible. If I remember correctly they recommended I install it between the strainer and the raw water pump. If no bubbles noticed then install it after the raw water pump and check again.

 

[Lazy Daze]

Here's a test you can do (in the water) to see if you're at least getting enough flow to the heat exchanger. You'll be measuring the amount of water that comes out of the hose that attaches to the heat exchanger (the supply hose). Remove it and direct it into a bucket. Do this with an cold engine. Run the engine at exactly 1,000RPM's for 15 seconds. Measure the amount of water. It should be roughly 7.5 quarts. Do it 3 more times. This will at least verify if everything is good up to this point and help to point you in the right direction.

Did you closely inspect your hull intake?

 

[dwna1a]

I would like to post these photos here. Hose line, housings, check them all! Notice the housings looks great, keep looking.
Flushing the block at the block drains are a must!

 

[D Bell]

My two cents….install the clear hose at the Trans Cooler input from the pump. HD sells a 1 1/4 ID stiff vinyl hose. A 3/4 PVC 45 degree elbow coupler works to join (need 2 hose clamps). You can then see the flow from the pump and isolate if it's before……bad impeller or collapsed hose, ……… or after. If flow is there (at idle), move up the hoses cleaning along the way. The heat exchanger was the biggie for me. Bits of RTV gasket goo from the endcaps was stick everywhere. An insulated 14-16 gauge wire reaming the tubes and a brass nozzle hose blow out cleared it all. No removal necessary.

Flush everything backwards from the manifolds/risers.

Old impeller deposits were at the trans cooler but the RTV goo on the heat exchanger (and little rubber parts) was unbelievable.

 

[dwna1a]

I used this trick,..Ty Ty ty

 

[Goatz]

When we get the heat exchanger back I will do the clear hose thing between the strainer and pump, and pump and trans cooler. We have the hose already. I use it to run intake into bucket when we start engine on the hard.
The heat exchanger should be perfect when we get it back from shop, so should be able to remove from equation.
Flushing block is a good Idea! I will have to see if I can get the plugs out. I did flush one of the exhaust manifolds and planned to do the other when I start to put it back together.
Was also reading up on cockpit heater. Manual says heater should not be higher then heat exchanger. Well from the factory I would say it is at least a foot higher so.... Also need to check and makes sure we did not mix up the hoses going to the heater when we removed engine last year. The supply should be from the intake manifold and return should go to water pump. Much to check. Hope to get down to boat this weekend but also still waiting for heat exchanger from shop.
Thanks for all the responses.