Suzuki overheat

[landry]

My friend has a new used boat with a 1999 70hp 4 stroke Suzuki. Runs really well. However, yesterday the overheat alarm came on after a 15 minute high speed run.

It has a new impeller btw.

Anyone own one of these and have a similar issue.

What's the most likely cause.

[ccmtcanada]

Here's an excerpt from another Suzuki owner....

 

"It appears at this point that the problem was being caused by the motor picking up air while being run under certain conditions. Lowering the motor by one mounting hole seems to have corrected this condition. According to the technician, small amounts of air were likely being sucked into the cooling systemespecially when running across a light chop at high speeds. Once inside the motor, the tiny bubbles would coalesce to form air pockets, which in turn would create hot spots along the cylinder walls and in the head. Hot-spots equal steam, and steam in the system creates a temperature spike and eventual overheating. Shutting the motor down (to cancel the alarm and the guardian mode) allowed all the water to drain. When I would restart, the air pockets would be eliminated as fresh water was again flushed through the system."

 

Another thing I read was if the pee stream wasn't too warm, then it could be a faulty sensor.

 

Hope you figure it out!

[landry]

That very well could be it. Light chop and long run. Thanks. I will check the stream temp next time. It ran great after we shut it down. While he got the trailer I ran it hard for ( minutes with no issues.

[finja]

I had my Suzuki df140 overheat this year at wot. I was very surprised since the outboard is only 3 years old and runs smooth as a top. Took me a while to figure it out but when I had my skeg repaired this winter, the intake on the lower unit for water pickup was installed backwards. So at high speed the water was being pushed away instead of into the water pickup. Worth a quick check if the lower unit was serviced recently.

[ecmilley]

Uts a 99 when was the last time the impeller was changed?

[landry]

It has a new impeller. Bay City marine did it. I m sure it is correctly done. Good flow at pee hole.

[ecmilley]

well with the couple i service either suke or evinrude johnson four stroke the alarm at high speed is usually a fuel restriction,bad line filters ect.

had one case of a mpi suze alarm at low speed was a discharged battery

[ecmilley]

also possible theres crud build up on t-stat that effects flow when most needed

[landry]

Thanks ec.

We r gonna check the oil level/quality and the intake grates. Possibly it was trimmed up to much too???

[ecmilley]

usually if your trimmed up to much your water pressure goes down but your rpm goes way up, but not eing there to see it is a shot in the dark

[landry]

I think he may have been over trimmed but not sure. We were proposing a bit before it went off. So many variables. Lol. We will keep an eye on it.