Did I damage my Mercruiser 5.7L after overheating?

[Tahoeboater]

I have a 1997 Crownline with 5.7L mercruiser. While running at full speed, I noticed smoke from the engine compartment. opened up and did not see anything. Boat ran fine and temp was about 160, oil pressusr good. Continued to run. Boat started smoking very bad and engine quit. Noticed starboard side exhaust manifold rubber exhaust hoses were so hot one was burning. Diagnosed that water was fine from thermostat housing, but manifold clogged and the one side did not get water.

Never showed as an over heat via guage. After cooling, the engine run, but missing a bit.

Do you think I could have caused engine damage?

Thanks for your time!

 

[Bondo]

Re: Did I damage my Mercruiser 5.7L after overheating?

but manifold clogged and the one side did not get water.

Never showed as an over heat via guage. After cooling, the engine run, but missing a bit.
Do you think I could have caused engine damage?

Ayuh,.... Probably...

 

[Tahoeboater]

Re: Did I damage my Mercruiser 5.7L after overheating?

Doesn't the water circulate through the block as well, keeping the block/head from getting hot? Exhaust manifold would get hot. Maybe fry a valve. Anyone with experience as I assume I am not the first this has happend to.

 

[Tahoeboater]

Re: Did I damage my Mercruiser 5.7L after overheating?

Here is the final outcome (I love that I get no responses to this as this is supposed to be a forum of knowledgable individuals!). Now I am the expert!

The cooling water exits the exhaust manifolds after it cools the block. Blockage was at the starboard exhaust manifold and damage was done to the two hoses that attach to the riser and the Y pipe. Exhaust flapper was toasted. I bought a great set of used manifolds (90 fresh water original hours) for $260.00. Installed all new hoses (from Y pipe and riser) and cleaned both risers. Since the boat was out of the water, I replaced the thermostat and impeller for PM as they are very cheap, easy fixes. Boat runs VERY cool...no damage to the motor as the exhaust manifold is the only the only thing that got hot.

Boat is happy, healthy and back in the water!

 

[soaringhiggy]

Re: Did I damage my Mercruiser 5.7L after overheating?

great news.

good work!

 

[Bondo]

Re: Did I damage my Mercruiser 5.7L after overheating?

Now I am the expert!

Ayuh,... Some posts slip off page 1,+ we can only answer Soo many....

So,.....
Why was the motor Skipping,..??

 

[TilliamWe]

Re: Did I damage my Mercruiser 5.7L after overheating?

Ayuh,... Some posts slip off page 1,+ we can only answer Soo many....

So,.....
Why was the motor Skipping,..??

Yeah, sometimes you need to "bump" your own thread back onto page one or it gets lost.
Why was the motor missing a little?

 

[Tahoeboater]

Re: Did I damage my Mercruiser 5.7L after overheating?

I checked compression on all four Starboard cylinders and all at 120 plus or minus. The set of wires running to motor (in the plastic protecive slip shell) were melted to the pipe between the riser and y-pipe. I peeled it off and separated the melted wires. may have had a short to the pipe or together? Runs perfectly and now have a 140 degree thermostat (Lake Tahoe, CA only boat). Couldn't be happier so far!!

Thanks for the responses...This is my first post, so I will follow better on the next!

Thanks,
Keith

 

[fabrimacator21]

Re: Did I damage my Mercruiser 5.7L after overheating?

sounds good but I'd dump the 140 thermostat... motors like to run a little hotter then that.

 

[Bondo]

Re: Did I damage my Mercruiser 5.7L after overheating?

The set of wires running to motor (in the plastic protecive slip shell) were melted to the pipe between the riser and y-pipe.

Ayuh,... That's HOT....

Now you need to replace the Rubber Parts in the exhaust system,... I'm SURE the Shutters are Burnt...

 

[z284u2try]

Re: Did I damage my Mercruiser 5.7L after overheating?

I checked compression on all four Starboard cylinders and all at 120 plus or minus. The set of wires running to motor (in the plastic protecive slip shell) were melted to the pipe between the riser and y-pipe. I peeled it off and separated the melted wires. may have had a short to the pipe or together? Runs perfectly and now have a 140 degree thermostat (Lake Tahoe, CA only boat). Couldn't be happier so far!!

Thanks for the responses...This is my first post, so I will follow better on the next!

Thanks,
Keith

Did you check port side comp? Whats the stock comprssion on that engine?
Seems like you got lucky if thats all that was needed.

 

[Benoit Masse]

Re: Did I damage my Mercruiser 5.7L after overheating?

I have a 1997 Crownline with 5.7L mercruiser. While running at full speed, I noticed smoke from the engine compartment. opened up and did not see anything. Boat ran fine and temp was about 160, oil pressusr good. Continued to run. Boat started smoking very bad and engine quit. Noticed starboard side exhaust manifold rubber exhaust hoses were so hot one was burning. Diagnosed that water was fine from thermostat housing, but manifold clogged and the one side did not get water.

Never showed as an over heat via guage. After cooling, the engine run, but missing a bit.

Do you think I could have caused engine damage?

Thanks for your time!

Well, I'm just experimenting the same situation presently with my Maxum 2300sc with a 5L Mercruiser engine. Very very bad situation. All damages were caused by a bad thermostat who didn't open (stick). It happened the same way as you. On my 1998 Mercruiser engine, the sensor was moved beside the thermostat and that's why even if in appearence everything is OK, the gauge don't indicate any overheating because the fresh water who comes out by the exhaust when the thermostat is close still cooled the sensor. When I had stopped the engine after I have notice a lack of power, the temperature indicated on the gauge was going up over 200 degrees and alarm goes on???. So I restarted the engine and everything came back to normal in less than 15 seconds... because the cool water was refreshing the sensor again. What an engineer the guy who decided to located the sensor there. In the past apparently the sensor was located at the other end of the engine block so it was possible to prevent an overheating.

Final diagnostic for me: Two craked engine heads, damaged valves, etc.. I have to put a new reconditionned Merccruiser engine in my boat for the amount of 6000$....just because of a 25$ bad thermstat.

Hope it won't be as bad for you my friend?

 

[fabrimacator21]

Re: Did I damage my Mercruiser 5.7L after overheating?

6g's??????

you got ripped.

 

[fabrimacator21]

Re: Did I damage my Mercruiser 5.7L after overheating?

6g's??????



No offense but you got ripped.





Whoops. Double post.

 

[jtybt]

Re: Did I damage my Mercruiser 5.7L after overheating?

Benoit,
The difference between you and tahoe was, through negligent maintenance, Tahoe very nearly burned his boat up which may even have caused an explosion which could have caused loss of life. He was EXTREMELY lucky...and all he was concerned was that his engine wasn't damaged.

There's a very good lesson here that I hope people will take to heart. Preventive maintenance on a boat may save your life. Don't neglect it.