Specific Cooling Question...CONCLUSION!

[BAproject]

I am in the process of tracking down the reason my 4.3 mercruiser (1991) is heating up to 180 degrees at idle running on "muffs" in my driveway.

I have replaced circ pump, risers, hoses, and t-stat. Have not changed the impeller but pulled the pump feed hose off while running and there was plenty of water supply (no air in it)...it was actually a shocking amount of water that was shooting out!

Here's the question (or 2 I guess). The water feed hose is cool, the 2 hoses that go to the risers are also cool, the exhaust hoses (the ones with check balls in them) are hot and here's the question, is the hose feeding to the circulating pump supposed to be hot to the touch? I read the manual and I noticed that some hot water feeds back into the engine, but it seems really hot?

Any other causes for the overheating or the circ pump hose heating up (other than impeller)?

Thanks in advance, I am racking my brain trying to figure it out.

-BAproject

 

[Brentathon]

Re: Specific Cooling Question

Re: Specific Cooling Question

Details? Raw water cooled?
My raw water cooled; only the incoming hose from drive and the 2 hosed (from check balls) that go to the ELBOWS are cool; all other hoses are hot.
Low rpm over-heat is often due to improper check ball seating, and the cool water just goes right to the elbows, instead of circulating through the system.

 

[BAproject]

Re: Specific Cooling Question

Re: Specific Cooling Question

I see, yes it is raw water cooled.

There is some corrosion in there, but when I replaced the the t-stat I blocked the outlet to the circ pump hose to see if water would rush up and force the check balls out. It did open the check balls and shoot water. There is a chamfer where the check balls seat, they look OK to me...but not sure how to properly test.

How can you tell if the check balls are seated properly and what do they actually do? Any help would be great, I have read the manual but it doesn't give that much detail on how this system really works.

And I erred, the two hoses going from the check ball outlets to the risers are cool...if I am remembering correctly.

-BAproject

 

[Brentathon]

Re: Specific Cooling Question

Re: Specific Cooling Question

The hoses that go from check balls to Elbows allow all the "extra" cooling water coming from drive, to exit via elbows (without circulating through block). When T-stat warms-up and opens, hot water from block flows through T-stat and exits via manifolds then elbows; allowing more of the "extra" cool water to bleed into circulating system rather than just exiting via checkballs/elbows.
Water pressure (hose) of earmuffs should be high enough to have extra water squirting out from where the earmuff contacts the side of the drive.
Manifolds should be changed AT LEAST every 6 years on salt water.
You can replace the 4 hoses from T-stat housing to elbows and manifolds with clear vinyl, to "see" whats going on.
I replaced my original (1991) T-stat housing back in 2002.

 

[BAproject]

Re: Specific Cooling Question

Re: Specific Cooling Question

I am wondering if the t-stat housing is squashed. I can't figure a good way to diagnose it? Did you replace your housing with the same style?

Also, when I pulled the engine apart there was a lot of corrosion/blockage on the passage of the starboard side head (where water comes up from the jackets). I think I cleared it out pretty well. Could this be causing a problem as well?

The risers are new, but should I pull the manifolds and inspect them...ugggg

-BAproject

 

[Brentathon]

Re: Specific Cooling Question

Re: Specific Cooling Question

I have a 5.7 Merc Alpha One Gen I, so my T-stat housing had to be the new style with the brass Tee (which is actually the original style); since the one-piece casting style is no longer available for my engine.
The brass tee style is awesome, anyway, since the brass tee for the check balls never corrodes much.
Any/all blockage is an issue. If you don't know the age of the manifolds.....then that's a pickle......I personally would replace them, then.
Usually, the block and head passages stay fairly clear...for a long time.....15 or more years? If you cleared-it, and there's large passages...then I don't know.
I just went through an issue where my Sierra brand impeller was pumping too little water.......but that was at high rpm. I would change impeller if I were you.
One way to kill these engines, is OVER-HEATING. I believe it's the number one killer.

 

[BAproject]

Re: Specific Cooling Question...HELP PLEASE

Re: Specific Cooling Question...HELP PLEASE

Thanks for the reply. The manifolds "looked" clear when I pulled the risers but that was a bit of a topical inspection.

I am going to replace the impeller, which may be a problem at higher speeds but not at idle. At higher speeds I wouldn't be surprised if it was slipping. So I am going to do that regardless.

I have a sneaking suspicion that this is not the root of the problem though. I really wonder if the t-stat housing is trashed and maybe a clog somewhere in the manifolds....although the flow seems good. I don't want to go around just replacing parts to no avail, exhaust manifolds are not cheap to replace not knowing if that's the problem.

What is the best way to inspect the manifolds? Anyone?

 

[Don S]

Re: Specific Cooling Question...HELP PLEASE

Re: Specific Cooling Question...HELP PLEASE

The water feed hose is cool, the 2 hoses that go to the risers are also cool, the exhaust hoses (the ones with check balls in them) are hot

The hoses that come off the thermostat housing fittings with the check balls in them are supposed to go to the risers.

 

[Brentathon]

Re: Specific Cooling Question...HELP PLEASE

Re: Specific Cooling Question...HELP PLEASE

Many people don't even bother to "inspect" risers and manifolds.....including me. I change them after a length of time, as they truly are periodic maintanence-type items....they are not supposed to be items that you "run until they fail".
Same thing with O/D impellers. And engine circ pumps should also be replaced before failure. T-stats, too., etc. etc. etc.
I believe, even the cast iron t-stat housings should be replaced if they are 10+ years old, and used on salt water, and not flushed after every use.
I think a long block is one of the few "use until it dies" item in the powertrain.
I'm even worried about my original (1991) intake manifold...

 

[rlbrooks99]

Re: Specific Cooling Question...HELP PLEASE

Re: Specific Cooling Question...HELP PLEASE

There's a thread on here that discusses this and how the springs can lose some tension and cause overheating. http://forums.iboats.com/showthread.php?p=2747870#poststop Take a look at this thread - http://forums.iboats.com/showthread.php?p=2747870 (just maybe?)

 

[BAproject]

Re: Specific Cooling Question...HELP PLEASE

Re: Specific Cooling Question...HELP PLEASE

Yes Don S. thank you, this is how my system is set up, in fact that is exactly the page from the manual I downloaded.

I think the t-stat housing is trashed, I bought it off craigslist as it looked 100times better than the one that came off the engine, but it might still be suspect.

It seems like I am getting good flo-thru the exhaust system....so my immediate thinking is that something is being mis-diverted inside the t-stat housing.


Any way to test gpm's being supplied on the inlet of the housing?

 

[Brentathon]

Re: Specific Cooling Question...HELP PLEASE

Re: Specific Cooling Question...HELP PLEASE

There's an impeller test that tests incoming flow at 1500 rpm. I think it's a service bulletin for Alpha drives.
You run a hose in the bucket for a brief period, and measure how many quarts are pumped from O/D.

 

[BAproject]

Re: Specific Cooling Question...HELP PLEASE

Re: Specific Cooling Question...HELP PLEASE

will look into this...thank you

 

[CheeseCutter]

Re: Specific Cooling Question...HELP PLEASE

Re: Specific Cooling Question...HELP PLEASE

There's an impeller test that tests incoming flow at 1500 rpm. I think it's a service bulletin for Alpha drives.
You run a hose in the bucket for a brief period, and measure how many quarts are pumped from O/D.

The attached picture is from Manual #18 for a 1993 4.3. Your engine is not covered by this manual, but it gives you an idea of volumes. The test is to be done at 1,000 RPMs for 15 secs.

 

[BAproject]

Re: Specific Cooling Question...HELP PLEASE

Re: Specific Cooling Question...HELP PLEASE

easy enough....one quick question about that. This means that the engine is basically running dry for the equivalent of a minute ( 4x 15 seconds), isn't that really bad for it?

 

[StevNimrod]

Re: Specific Cooling Question...HELP PLEASE

Re: Specific Cooling Question...HELP PLEASE

Had the same issue earlier this season when getting ready to put in - running warm on the muffs. Turned out to be my muffs. I got the "professional" ones at West Marine and they're a bit stiff. My mechanic took them off and put on one of his muffs (where the muffs are a bit more "floppy") and we had no problems after that.

Maybe the installation of the muffs was the culprit or the muffs themselves, but that's what worked for us.

 

[CheeseCutter]

Re: Specific Cooling Question...HELP PLEASE

Re: Specific Cooling Question...HELP PLEASE

This means that the engine is basically running dry for the equivalent of a minute ( 4x 15 seconds), isn't that really bad for it?

The impeller is still in water so that would be fine, and if you do this while the engine is cool enough (thermostat NOT opened), you do have water flowing through the engine.

 

[BAproject]

Re: Specific Cooling Question...HELP PLEASE

Re: Specific Cooling Question...HELP PLEASE

awesome, makes sense....I have a feeling this diagnosis is going to be more difficult then planned, but this seems like a good place to start.

 

[BAproject]

Re: Specific Cooling Question...HELP PLEASE

Re: Specific Cooling Question...HELP PLEASE

Hey guys....at a loss!!!!!

New thermostat (140 degree)
New hoses
New circ pump
New Risers
New impeller (lower unit), gaskets, and wear plate
Replaced gaskets in risers with required restrictor gaskets
New belts

All parts are quicksilver.....


engine is still doing the same exact thing. Comes up to temp, t-stat opens, then slow creep to about 165.....give it about 1500 RPM (guess but not revving too high, tach doesn't work) and shoots up to almost 200 degrees....then I shut down immediately.

To take the muffs of the loop I filled a large bucket with water (and a hose in there with continuous supply) lowered the outdrive and completely submerged it to make sure there was adequate water going into engine.

What can be the problem here.....I am really frustrated!

-BAproject

 

[BAproject]

Re: Specific Cooling Question...HELP PLEASE

Re: Specific Cooling Question...HELP PLEASE

Just wanted to refresh my previous post now that everyone is back being on the water all weekend

Any thoughts from my post above....

Another update..... I pull the feed line out of the boat this weekend (while you were all cruising around), I thought the power steering cooler might be clogged, it wasn't nothing came out and had good flow....

And the saga continues!

-BAproject