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Mercruiser 230 V8 engine overheating problem

N

nmoye1

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"I just bought a 1986 Searay m

"I just bought a 1986 Searay mid-cabin with a 230 mercruiser V-8.When I bought the boat the owner stated to me the engine needed a new water pump due to it overheating on him.He stated that the last time he took the boat out it overheated on him and caught the two exhaust bellows on fire.He stated that it was because barnacles were covering the intake holes in the sterndrive.Since I bought the boat I have replaced the water pump in the drive unit.The old one did not appear to be in bad shape at all.I remved the water intake pieces in the drive leg and cleaned them of all barnacles and reinstalled them.I also checked for any obstructions from the intakes to the gimbal.All seem great.I then replaced the exhaust bellows.I took the thermostat housing apart and found the thermostat to be rusty and in unknown condition along with some debris sitting on top of it.I replaced the thermostat and then reassembled the thermostat housing.While the thermostat housing was apart I ran a hose to flush out the engine block and all hoses.My problem is that the engine runs at 150 to 160 degrees at an idle or just above without overheating, but when I go any faster and try to get up on a plane the temp quickly rises.When I bring it back to an idle the temp goes back down.I also noted white smoke at the back of the boat and the exhaust smells kind of rich.I verified the correct engine timing at idle.I took the exhaust manifolds and elbows off but unsure what to look for on these.The exhaust manifolds appear to be in good shape but the exhaust elbows I don't know.Is there any way to check the operation of these items.Any help would be appreciated."
 
elbows possibly blocked? head

elbows possibly blocked? head gasket? are these original manifolds? way overdue for salt water.
 
Not sure if they are the origi

Not sure if they are the original manifolds or not.The elbows could be blocked but unsure what to look for on them.Is there anyway to know for sure if head gaskets are bad.
 
I'm assuming it is sea wat

I'm assuming it is sea water cooled.

Doubt a blown head gasket (although you may have a blown gasket if it was overheated hard) would cause it to overheat at higher speed/load conditions.

The smoke/steam you are seeing may be the result of water "re entering" the heads and manifolds and boiling off into steam.

If you know you have good pumps... look for a water obstruction. That would be my first action. Remove the t-stat (look for more debris) and run it without a t-stat and let me know what you find out.
 
also - is there any water in t

also - is there any water in the oil? WOuld show up as brown sludge. You would see it under the valve covers and perhaps on the dip stick.
 
"Suggest you get a compression

"Suggest you get a compression test on the motor before going any further. When water is cut off to a (I assume) raw water cooled engine, it can self-destruct in less than half a minute (if running along on plane).

Good luck!

Jeff"
 
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