Marine: Boating, Sailing, PWC, GPS and Navigation - help with 25 hp merc tiller model

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walleye_bill
07-28-09, 05:16 AM
i have a 1987 or 88 25hp merc outboard tiller model.
i am getting a good piss stream out the back, but when at top speed, i have noticed the top of my upper unit, and the cylinders are getting extremely hot.

i troll alot and at a slow troll its luke warm to almost cold. does anyone know what temp this motor should be at at full throttle.

or if anyone has any advise on why the sides of the upper housing, and the cylinders are getting so hot.

i put a new impeller in it last season.

samuari
07-29-09, 09:15 PM
The cyl head temp should be about 160. I would pull the thermostat and run it on a hose look for good flow, if it flows replace the thermostat.
walleye_bill
07-30-09, 04:37 PM
your the only one to leave one . the only problem with that is, i dont think my motor has a thermostat.
atleast it doesent mention one, or how to replace one in my entire manual.
ill try to get a thermo gun to check the temp on cylinders. thanks.