What damage do you check for after overheating?

[billh1963]

Let me start by saying I know that what I did was stupid....I should have understood how my motor is cooled before I went on the water!
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I overheated my 1997 Volvo 7.4L (454) and was wondering what kind of damage I should look for? The engine is RWC and has new risers/manifolds.

A couple of months ago I was cruising in the sound and the engine alarm went off. I immediately looked at the temp gauge and saw it was around 220 and I shut it down. I opened the hatch and saw that I had broke a belt on the front of the engine. The belt was to the alternator and to the engine water pump (not the raw water impeller). At this point I got stupid. Stupid me thought only the alternator was affected thinking the raw water impeller supplied all cooling to the engine. (I didn't think about the engine having a water pump). Anyway, I let the engine cool down and I started it up. It ran fine for a few minutes (the risers were cool) and started overheating again. I shut down and repeated this cycle several times until I made it in. I assume I was able to do this because the raw water pump was pushing enough water into the engine to keep it relatively cool.

Since then I have not had a chance to put the boat back in the water but I have replaced all the belts and the thermostat. I will be off for almost two weks over Christmas so I want to run the boat. The engine starts and runs fine "on the hose"; however, before I put it in the water is there anything I should look for? I assume I should do a compression check. What else should be checked (and how do I check it)?

Thank you.

 

[Don S]

Re: What damage do you check for after overheating?

220? will not damage the engine, but the lack of cooling water to the exhaust could cause the hoses that come off the risers and go to the Y pipe to burn inside. I would sure pull them off and inspect. If they are all crispy, replace them. That model also had exhaust shutters that would burn off and get stuck in the exhaust passages. Check them and make sure they are accounted for. IF they are damaged, remove them and throw them away. Volvo stopped using them around 98 or 99 as I recall.
You might also want to look at your pulleys and make sure they aren't all rusty, if they are, that is what caused your belts to break. Clean them up and repaint so they don't grind your belts away. Might also want to inspect the raw water pump impeller. It should be replaced everyother year anyway.

 

[mickjetblue]

Re: What damage do you check for after overheating?

What kind of shape is your motor oil in? I would change the oil and filter,
all the same. If you really didn't over overheat the engine, and the oil
did not break down its lubricating ability, and didn't burn out, you might be ok. Otherwise...

 

[billh1963]

Re: What damage do you check for after overheating?

The oil looks clean but changing the oil is a good point. I'll do that before I put it in the water.

The impeller is new.

The pulleys are a little rusty so I'll clean them up. I thought the rust would wear away from the belt rubbing. I didn't think about that damaging the belt.

Bill

 

[flabum]

Re: What damage do you check for after overheating?

Although engine damage is unlikely, a quick compression test wouldn't hurt.

 

[billh1963]

Re: What damage do you check for after overheating?-UPDATE

Re: What damage do you check for after overheating?-UPDATE

Update.....I put the boat in the water over the holidays. I decided to change out all the hoses, raw water pump, thermostat, etc. The air temp was around 70F and the water was 53.8F. Engine ran nice and cool (145F at idle and 155F at speed). No water in oil or anything else.

Thank you for the help!

 

[Haut Medoc]

Re: What damage do you check for after overheating?

Ya dodged a bullet!...
Lucky you!......​