Mercruiser 180hp, 4 cyl, 1987

[Hudson River]

Problem - running hot, 180-185 when on plane. When decrease speed, temp. comes back to 160 (which is correct reading). Steps taken to resolve the problem: new impeller, checked all tubes in outdrive, checked intake, new hose from outdrive to transom, new hose from transom to voltage regulator, new thermostat, new exhaust elbow. Replaced exhaust manifold, cleaned heat exchanger. Checked all hoses - everything appears OK. Tried 2nd thermostat (just in case). Can run at 1500rpm with no problem - pick it up to 3200 and the temp. rises.

Have I missed anything? Any suggestions?

 

[Bt Doctur]

Re: Mercruiser 180hp, 4 cyl, 1987

"replaced impeller" full kit including base or just the impeller.
the base may warp and allow hot exaust to enter the pump.

 

[Big Boat Bay Buster]

Re: Mercruiser 180hp, 4 cyl, 1987

I have an 83 470. When the outside water temps peak at around 75-80 degrees, the engine temps will climb to 180 when on plane. This is with a 3 inch heat exchanger. What size exchanger so you have? I bought a 4 inch to help it run cooler, but I have yet to put it in! I don't consider 180 to be an overheat condition. Food for thought, Chris

 

[rodbolt]

Re: Mercruiser 180hp, 4 cyl, 1987

with only memory I think the merc manual says the operating temp range on the MCM 4 cylinder is between 160 and about 200 .
your well within that.
DonS will have it soon maybe but all my manuals are still packed away.

 

[Don S]

Re: Mercruiser 180hp, 4 cyl, 1987

IF you normally run at 160? and now it runs at 180 to 185, then yea, you have a problem.
If you have the 3" heat exchanger and now the boat is running 20? hotter than normal and everything else (Where, how fast, how long, boat load, etc) is the same, you have a problem.
Could very easly be the raw water pump housing, might try cleaning the heat exchanger (radiator shop could boil it out.
How old is that hose between the drive and the transom shield. Is it kinked or the hose delaminated inside? Seen that happen a couple of times. Also check it to see if it's kinked.

 

[rjevans]

Re: Mercruiser 180hp, 4 cyl, 1987

How hard is it to change a 3" stock heat exchanger, to a 4" on a 470 mercruiser?

 

[Don S]

Re: Mercruiser 180hp, 4 cyl, 1987

Start a new thread with your question rjevans, or soon your post will be lost.