Engine suddenly overheating

[geekeasy]

I was out motorsailing yesterday, and when I looked down at the temperature gauge it jumped from 170 where it usually is, up to 240 maxing out the gauge.

It's a raw water cooled engine.

And some water is coming out with the exhaust, but it seemed like less than used it come out.

Any suggestions for the operation to solve this problem?

1) Check the water filter.
2) Pull and check the impeller
3) ....

I checked the water filter first because it's super easy, and it was clean. I pulled the impeller second and it looked fine. There was one very small piece of plastic in the fuel pump, but did not seem that likely that would cause the problem.


What's next?

Get in the water and check the intake?

[Antibes]

You can check intake by removing hose from the water intake shut off on the inside of the boat.

[geekeasy]

3) I checked the intake as Antibes suggested. The water flow was fine.

4) I pulled the thermostat. There were a bunch of chunks of rust at the bottom of that housing. I cleaned it out. I might put it back together without the thermostat.

5) I pulled the hose running to the thermostat. It seemed partially blocked. I cleaned it out.

6) I ran high pressure water through the manifold, a tiny bit of rust flakes came out but it seemed fine.

Overall, I haven't found any "magic bullets" yet that seemed to be the problem.

Any other ideas?

[Mo]

My pet peeve.

I'll make this easy. I know of only 2 people here in Halifax area that run with a T-stat...they generally stay at the dock and know all there is to know about the A4 and sailing ... both...but I've never seen them pull a rabbit out of the hat on either. Those of us that push our boats through significant seas on a regular basis run without a Tstat and use a by-valve about 1/2 open. I was told by Donny Webster to drop the T-stat and never had to look back. The guys that I know that run their boats...most are OLD...REAL OLD...we are talking 40 years experience based knowledge here. Those that don't listen go though problems on a regular basis, however we never hear from the ones that got it right regarding cooling issues. I've only had an A4 since 2007....but the guys I know have had them since 1977. So, remove the T-stat, install a by-valve and run your engine overheating issue free for the next 40 years or next owner...whichever comes first.

...do a compression test to see if you didn't loose the head gasket over this, OK.

PS...if, once the Tstat removed and it is still steaming you do two things
-compression test
-check the NPT fitting at the outlet side of the exhaust manifold. (The one that has the small hose going to the hot exhaust) Sometimes they can block and cause trouble.
...I took into account that you checked the intake...if not so, you need to close intake valve, remove hose, have a 1 ft broom stick handy...open valve and as the water comes in punch the broom stick down and SNAP back quickly....pull it out, close valve (a little water will have come in), put hose back...start engine. (By this time any obstruction should have moved away from the intake).

All the best.

[Dave Neptune]

At 170 in salt water you are just asking for problems with salting up. If you see bits of rust rolling out it is time to flush and then follow Mo's advise especially UNDER the exit fitting on the manifold!! Note you must remove the fitting!!

I have run without a t'stat since 1983 and the engine is original in my Ericson running strong on it's 45th year of service and it is original. I motor at least 100~150 hours a season usually in 5~6 hour increments.

Dave Neptune

[BunnyPlanet169]

3) I checked the intake as Antibes suggested. The water flow was fine.

4) I pulled the thermostat. There were a bunch of chunks of rust at the bottom of that housing. I cleaned it out. I might put it back together without the thermostat.

5) I pulled the hose running to the thermostat. It seemed partially blocked. I cleaned it out.

6) I ran high pressure water through the manifold, a tiny bit of rust flakes came out but it seemed fine.

Overall, I haven't found any "magic bullets" yet that seemed to be the problem.

Any other ideas?

Do you have a bypass valve or not? Without the thermostat, how's the water flow if you clamp off the bypass loop? Rust crispies under the thermostat come from only one place - the inside of the block.

My RWC A4 would idle and run at low RPM and 150 degrees... Until I needed power, and then it would go ballistic and start steaming. Root cause: just enough flow through the block, but mostly clogged up in the block and head. The bypass loop will mask this problem - clamp it off to test.

[romantic comedy]

Mo, I run with FWC and the original t stat. Stays steady 180

[JOHN COOKSON]

Mo, I run with FWC and the original t stat. Stays steady 180

????????
I run FWC with the original thermostat. Stays steady 150*.

TRUE GRIT

[Ajax]

I've been RWC with the original style t-stat, and running at 130-140F like clockwork, under all conditions.

[geekeasy]

I'm 95% sure that I don't have a bypass valve.

Though there is something in the hose leading to the thermostat housing which restricts the flow.

I haven't taken the boat out of the slip yet for a real test, but once the thermostat was removed the engine was running very cool.

Thanks for your help everyone.

[sastanley]

by-pass!!

geek..that restrictor IS the bypass valve...it's job is to reduce the amount of bypass cooling water that flows over and past the t-stat and force more water into the sideplate (block) behind the alternator and normally it helps cool the motor more.

Check out this pic of my motor from a couple years ago..you can see coming into the thermostat housing that I have the Moyer standard issue bypass valve..

[romantic comedy]

????????
I run FWC with the original thermostat. Stays steady 150*.

TRUE GRIT

John, with FWC we can run hotter. The engine likes it that way.

[JOHN COOKSON]

Don't start typing until your brain is engaged - I keep telling myself.
Sorry I mixed up RWC & FWC.
I'm raw water cooled.

TRUE GRIT

[Skywalker]

FWIW

1966 original A4. FWC. Original t-stat. Long Island Sound water temp in 60s.

170 degrees.

Skywalker