need help with merc problem

[niner93]

I have a problem with my 88 150 hp merc. The motor itself runs fine. The problem I'm having is that after about a 5 minute run at moderate to high speed it wants to overheat. I've had it into a marina and they could not find anything wrong. Has anyone else had a problem like this?
Any advice would be appreciated.

[ESOX]

A couple of possible problems:

When was the last time you had your water pump impeller replaced?

Is it running lean?

Is the timing too far advanced?

If the impeller is in good shape, have you checked to make sure you don't have a partially clogged water jacket?

[grizzly]

Niner93, had the same problem with my 1994 mariner, it turned out to be a bad head gasket. I replaced it myself in about 2 hours. Do you notice if the water spits good then like it wont spit as good for a second or two. Check for that, but as Esox said also maybe impeller and jacket could be an easy fix.

Goodluck.

Grizzly.

[niner93]

Thanks guys I'll give it a look. The one thing was that the marina did check the water pump and that was working fine. I was wondering about the oil pump.

[ESOX]

If the oil pump weren't working, it would be painfully evident after 5 minutes at a moderate to high speed.:eek:

[grizzly]

Esox may have nailed it, Check to make sure your o ring on your oil jug is seating correctly, air will get into the tank and will cause your auxilary tank in the motor to get low sounding the alarm, this is a good possibilty also. If you have filled your oil jug recently then it may be the ticket. Good work Esox, keep brainstorming and we will have this thing fixed.

Goodluck.
Grizzly.

[niner93]

:) As a matter of fact I did recently fill it with oil.
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