Engine overheating

[chfbledsoe]

I have a 1987 bayliner with an OMC 5.7ltr sterndrive. I just finished rebuilding the the engine and it seems to be running hot. It's running about 225 degrees. I have replaced the thermostat, water pump and impeller and tightened all the hoses. Still it's running 225 degrees. I tried to check water flow at the thermostat from the raw water line and the water pump line. It doesn't seem to be circulating well. Could thier be somthing restricting the flow between the impeller and the thermostat housing? Also noticed that when it gets hot that thier seems to be steem from the exaust. Sound like exaust manifold leeking? How do I tell which one it is? Could this cause the engine to run hot? @#$?&%$#@ PLEASE HELP!!!!!!!!!!!!!!!!! Any suggestions would be greatly appreciated.

 

[Uraijit]

Re: Engine overheating

Did you get your hose routing right

 

[jerryjerry05]

Re: Engine overheating

How old are the manifolds?Pull the water pump impeller and look for obstructions in the hose.
Maybe when you removed the manifods the corrosion in them came loose and is clogging the risers.
You need to flo test the man/risers. Jerry

 

[chfbledsoe]

Re: Engine overheating

Hoses are roughted right. Ilooked today and thier isnt any water flowing through to the cooler just on the inside of thetransom. Not sure how old the exaust manifolds are. I bough the boat about 4mths ago. It sat for about 2yrs befor that. I'll try checking for blockage. Do I need to pull the outdrive again to properly do so or can it be done with it on? How do I flow test the manifolds?

 

[tallguy63]

Re: Engine overheating

Is the timing correct? Is there a timing advance that needs to be considered? Does the carb need tuned? Could a lean mixture be causing the over heating? Was the carb rebuilt? Maybe it is not a water issue... just thought

 

[Boatin Bob]

Re: Engine overheating

When you replaced the impeller were there any vanes missing from the old one? That is probably the power steering cooler that the hose goes to from the transom and then up to the t-stat. You may have a blockage in the hose coming through the transom and will probably have to remove the drive again.

 

[chfbledsoe]

Re: Engine overheating

After taking the inpeller housing back off I back flushed water through the sytem starting at the cooler. some trash came out stuff like parts of an old impeller and impeller gasket. So with much hope I put it all back together and --------------------- no such luck. Still getting hot. I'm going to check the timing next. I did take the water lines off of the exaust manifolds to make sure tehy were getting water flow and they are so I'm going to take tallguy63's advice and check the timing. The carb was not rebuilt but seems to be working properly. Good fuel flow, no smoke in the exaust, idles smooth. If thier are some other test i should run I would love to hear about them.

 

[Maclin]

Re: Engine overheating

The exhaust manifolds or risers could still be the culprit if they are clogged internally with corrosion or whatever. If there is restriction in the manifold/riser exit flow then it does not matter how good the flow is up to the manifold, it will be stymied right there and the engine will run hot or overheat.Are you getting good water flow thru the exhaust, no vapor or steam?

 

[Maclin]

Re: Engine overheating

Also, running that hot could have melted any rubber exhaust components that are after the risers, like flappers. If those melted from the first overheat then they could have been forced down into a bad place and be blocking the water's exit as well.

 

[chfbledsoe]

Re: Engine overheating

I get vapors when its hot (up around 200). I'll check the flappers next. should I take the manifolds back off and put some compressed air to them and see if I can knock anything in thier free or is thier a way to test the flow trough the manifolds?

 

[chfbledsoe]

Re: Engine overheating

I also noticed that I don't have water running from the exaust. I'm pretty sure that it used to. Probably blockage in the manifolds/risers?

 

[Don S]

Re: Engine overheating

Ilooked today and thier isnt any water flowing through to the cooler just on the inside of thetransom.

The power steering cooler is the first thing the water from the outdrive raw water pump see's before getting to the engine.
If you don't have water to the cooler you have pump problems or plugged lines to the cooler.

 

[Uraijit]

Re: Engine overheating

I also noticed that I don't have water running from the exaust. I'm pretty sure that it used to. Probably blockage in the manifolds/risers?

I'd start by removing the hoses, and back-flushing each hose individually. Starting with the inlet hose, and moving forward in the system. Inlet hose on drive, then hose between heat exchanger and drive, then water pump to heat exchanger, then remove the thermostat housing, and flush engine, then exhaust manifolds. Finally, I'd remove the risers, and flush them separately. Then run a water hose down your exhaust Y-Pipe, and make sure you've got good flow. Once every piece is separately flushed, and has good flow, put it all back together.

You'll be able to identify areas with restrictions this way, and then you can start working on getting them cleared. Don't just flush one part and think that it's fixed. Check each area of the system separately, and make sure you get ALL the junk out of there, or it will end up plugging something else up later on. I'm thinking you've still got parts of a water pump impeller somewhere, or several "somewheres".

 

[bruceb58]

Re: Engine overheating

I did take the water lines off of the exaust manifolds to make sure tehy were getting water flow and they are so I'm going to take tallguy63's advice and check the timing.

Like Maclin already said, since water is getting to the manifolds, you need to check the manifolds, risers and beyond.

The question I would still have is what type of flow were you getting at the manifolds.

You at least need to pull the risers and see what those water passages look like.

 

[chfbledsoe]

Re: Engine overheating

Thanks guys! I'll get started on back flushing the system tommorrow. Any thoughts on the steam/vapors in the exaust? Oh yeah I did the water hose test on the y-pipe and it seems to have real good flow. I took the risers off to check the passages and the risers look O.K. but the port manifold looks like it could have some flow problems so I'll take them off tommorrow. whats the best way to back flush the manifolds?