1998 Mercury 150 Off shore - OVER HEATING ALARM ISSUE

[Ant-Knee]

Hello All.

I have a 98 mercury 150 Offshore 2 stroke model# 1150422UD, S/N # OG740674

the overheat alarm went off the second to last time I went out on the boat. Did not really seem to be that hot tho.. The teltale has a nice solid stream coming out, I went ahead and change the water pump and thermostats, But I took the boat out again yesterday and the alarm went off again..

I am going to change the poppet valve ( waiting for kit ) and both the temp sensors, The one on the port side of the motor looked pretty beat up and looks like the wires might be bad the starboard side did not look that bad but I am going to change that as well.. I am hoping this will fix the issue, But if not what else could it be..

Heres what will be new when parts get here,,

Temp Gauge ( On order )

Poppet valve kit ( On order )

Temp sender units ( Both On order )

Water pump and thermostats ( already in motor)


Is there anything else that could be bad in the cooling system and causing motor to over heat?

Any help is appreciated..

Thank you,

Ant...

 

[Robs88]

Re: 1998 Mercury 150 Off shore - OVER HEATING ALARM ISSUE

Get yourself laser temp gun, take boat out and try and get an accurate reading on your heads temp, engine my not be overheating at all could be a bad temp sender unit.

 

[Ant-Knee]

Re: 1998 Mercury 150 Off shore - OVER HEATING ALARM ISSUE

Get yourself laser temp gun, take boat out and try and get an accurate reading on your heads temp, engine my not be overheating at all could be a bad temp sender unit.

I am waiting on the temp gauge in the mail and was hoping that would give me a more accurate temp reading.. I am hoping it is a bad sensor or the poppet valve, Should have new parts in boat bye Friday, Should be back on water Saturday this weekend..
Will post what happens when I return..

Thanks for your reply!!

Ant...

 

[Ant-Knee]

Re: 1998 Mercury 150 Off shore - OVER HEATING ALARM ISSUE

Got all parts in and on the boat, Ran the boat on a hose today and it seems to be running at 140 - 145 degrees, .. Think this is normal.. I will take the boat out this weekend and run it.. What is normal temp when running say at 5000 RPM? and also what is too hot?

Thanks for any input..

Ant..

 

[aussieflash]

Re: 1998 Mercury 150 Off shore - OVER HEATING ALARM ISSUE

On my V6 temp alarm activates at 240 deg located below #1 plug.Outer head sender(on side of cyl head)is set at 190 deg.
I would think around 140ish would be a good temp at 5k.
Mine runs too cold at speed,still working it out.