88 50HP overheating at WOT.

[cbercaw]

Hello, My 88 50HP is overheating at WOT, I can only go about 2/3 throttle to keep the temp down on the guage. Impeller is brand new, no pitting on upperhousing or wear plate. Ive shot a clear stream of water through the thermostat hole (which opens in 135 degree water) down to the pump. (which opens at 135 in water) Any suggestions? Thank you.

 

[cbercaw]

Re: 88 50HP overheating at WOT.

Do I need to use a gasket sealer under the impeller wear plate? Because I didn't.

 

[pnwboat]

Re: 88 50HP overheating at WOT.

Is the water inlet screen free of any debris? Item 44 in the diagram below.


http://www.boats.net/parts/search/Merc2/Force/50%20H.P.%20%281988%29/507R8C/GEAR%20HOUSING/parts.html

 

[jerryjerry05]

Re: 88 50HP overheating at WOT.

Did you replace old or new part #50 when you did the impeller.J

 

[cbercaw]

Re: 88 50HP overheating at WOT.

I have no screen for the water intake..it broke out last year. Part number Number 50; the driveshaft seal? isnt that part of the upper pump housing. I reused the upper pump housing, it is less than a year old and looks fine.

 

[jerryjerry05]

Re: 88 50HP overheating at WOT.

There is a rubber seal that fits on the top of the pump housing.J

 

[cbercaw]

Re: 88 50HP overheating at WOT.

The rubber seal is torn, it always tears.I have replaced it many times..I do not know why it tears!. The pic is of an older, out of commission water pump, not the one i am using, but the driveshaft seal on the actual pump housing is ok on the pump in my outboard.

 

[jerryjerry05]

Re: 88 50HP overheating at WOT.

The old impeller:what condition was it in? Any pieces missing? The wear plate was it smooth or lots of grooves?The inside of the housing what condition?
Does the warning buzzer go off or just the guage reading high?J

 

[cbercaw]

Re: 88 50HP overheating at WOT.

The old impeller wasn't too bad, no pieces missing..the bottom was a little scorched. I replaced it, this one only has a few hours on it now,There is a tiny groove in the wear plate...the housing is in good shape, no pitting or marks.the warning buzzer got fried last year so i replaced it with this temp gauge....

 

[cbercaw]

Re: 88 50HP overheating at WOT.

the gauge reads about 135-145 but sometimes it tries to spike to boiling...I am afraid I fried the head gasket too because it got too hot a few times yesterday.

 

[erikpn]

Re: 88 50HP overheating at WOT.

Did you make sure you lined up and connected the tube from the water pump up with the intake tube on the motor when you put the lower unit back on? They will not automatically line up when you get the lower unit back on, you can EASILY miss and have the pump just spraying water up the side of the motor leg, not getting anything to the powerhead at all.

 

[cbercaw]

Re: 88 50HP overheating at WOT.

yes...I am thinking this is a thermostat issue....