Overheat Alarm 1995 150hp

[hitmanklep]

I bought my boat last summer and I'm still getting to know its like and dislikes.

In a no wake zones at low rpm (700/800) the overheat alarm activates after a couple hundred yards, when I bump it up to 1000 rpm I never get the alarm.

Does anyone have any ideas why the alarm activates? Is this a beginning to a problem?

Thanks

[jiggin joe]

Assuming this is your model no. you might consider changing pressure control valve and grommet as low rpm overheat can result from bad valve. You can find it here.
Yamaha Outboard Parts 1995 P150TLRT CYLINDER CRANKCASE 2 Diagram
parts 21and 23

It is a good idea to have a regular schedule of maintenance for water pump,thermostat ect.-

[rodbolt17]

assumining you have a 2.6L v6, ill second what joe said.
also when was the last water pump maint?

[hitmanklep]

I replaced the t-stats last year, thinking that was the cause of the alarm, but it didn't control the alarm. So for the rest of the season I ran it at 1000 or better rpm.
I am replacing the water pump this spring (I don't know when it was replaced last) and I will look into the pressure control valves as well. Is the pressure control valve the same as a popit valve? When I bought the t stats last year the man at the parts counter mentioned popit valves, I'm not sure what they are.
Thanks for the help and advice

[rodbolt17]

there is only one pressure control valve.
it CONTROLS water pressure in the block.
why did you not listen to the guy last year?
you may need an altenator.

[hitmanklep]

He did not have the valve the in stock, when I bought the t stats or I would have put that in also, and after figuring out I could run at 1000 rpm or better without issue, I figured everything was OK. The motor runs great and never had a problem pumping water
Why do you think I may need an altenator?
Thanks for the help

[rodbolt17]

the altenator was an inside joke.
actually not called for.
the valve isnt your issue, its the simple $1.40 grommet that needs periodic replacement and the grommet pocket cleaned.
takes all of 20-30 minutes unless its HPDI.

[hitmanklep]

LOL you got me
Are you sure its not the piston return spring?

BTW- its a carbed motor

[rodbolt17]

google mechanic verses customer.
you will get a laugh.
your describing a typical case where the valve no longer seals to the valve seat(grommet) and at low speeds the block wont stay full of water and typically #1 cyl overheats.
you should also note a decrease in tell tale water pressure.

[99yam40]

If you would always post your model # at the first of your thread nobody would have to guess as to what motor you are talking about

[hitmanklep]

I plan on doing that in the future (posting model number) but right now I am not sure of the exact model number and the boat is stored two hours away from me for the winter

[Ray Ritchotte]

I have a 150 pro V that was overheating and every one on the forum was trying to tell me that the heads were plugged up and I would not listen to them. After replacing everything that I could think of I finaly pulled the heads and sure enough all the water jackets in the block and heads were plugged. Cleaned them out and installed new gaskets and motor is running great. I will never doubt these guys on this forum again.
Ray