overheat at high RPM

kalla man

Petty Officer 2nd Class
Joined
Oct 5, 2006
Messages
100
uggggggggggh

1988 115 V4 rude'

overheat at high rpm only

I narrowed it down to port side cylinders
pulled the head and found a water reflector that was mushed down and blocking some water flow... and i thought that was my problem for sure!!
replaced it...cleaned out all salty deposits..and since i had the gasket set i did the starboard side too.

problem persists

replaced the thermostat and water pump about a year ago
she pumps water like a beast

so the only thing i can think to do now is replace the thermostat again

anyone with any other ideas before i do
 

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
Re: overheat at high RPM

What is the model number? Could be a water restriction.

What temp is it running?

If you remove the t stats, I would flush water up the water line to the t stat housing, then back flush from the t stat housing down the water line, to ensure free flow. Only remove 1 t stat at a time while doing this. It couldnt hurt to check the water pump while the lu is down.
 

Solittle

Fleet Admiral
Joined
Apr 28, 2002
Messages
7,518
Re: overheat at high RPM

You said that you replaced a water reflector. I think there are two - check your manual.
 

Solittle

Fleet Admiral
Joined
Apr 28, 2002
Messages
7,518
Re: overheat at high RPM

Two per bank that is for a total of four.
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: overheat at high RPM

Your engine must be newer than 1988, as they did not make a 115 that year. Check the valve body in the thermostat housing. There are two pinholes on that composite body that must be open/clear. If either pinhole plugs up ( a common occurrence) then that side will overheat. Those two holes let hot water bleed into the thermostat housing, causing the stat to open. One hole per thermostat.
 

reeldutch

Lieutenant
Joined
Feb 2, 2004
Messages
1,340
Re: overheat at high RPM

you might want to take the head covers of the cylinder head and clean it out.
i am sure there are some salt deposits or crud in there blocking water flow trough the head.
be careful not to break the bolts, use lots of heat and patience.
at higher rpm the thermostats are bye passed trough the pressure relieve valves.
it lets as much water as it can coming from the heads and dump it out in the exhaust at high rpm.
blockage in the cylinderhead slows down the volume of water gph. and there for loosing waterpressure after the blockage so it is not able to open up the poppet valves.(pressure releave valves.)

reeldutch
 
Top