Over heat alarm after slow speed running

[paw2000]

Hi, was out in the bay yesterday, ran about 5 miles to my favorite spot and did several drifts for flounders. After the 3rd drift, started up and went slow speed say 5 minutes as my buddy was on the phone. The alarm sounded and it was the constant overheat alarm. The motor was pumping a good stream of water. I shut it off, tilted the motor to check for anything on the lower unit, nothing. Restarted and still had alarm, decided to see what happens after it gets up to speed, and about 30 seconds the alarm shut off and was fine the rest of the trip. I have to travel slow speed on the river I keep my boat, so its never overheated before. Is it possible something passed thru the motor to plug off a water passage and then it finally passed thru?

The motor has new pump kit and themo stats installed this spring, I have run all over the Delaware bay and the only thing I noticed is early spring I would get some steam in the exhaust when at cruising speeds (20knts) I was told it was due to the cold 60degree water.

I read that there is a modification to the water hoses and thermo stats that bypass the water divertor valve. Would this be worthwhile mod for my issue?

 

[jonesg]

Re: Over heat alarm after slow speed running

What engine doh!
HP, Yr and model number..

But...a constant alarm is also fuel restriction in some models.
The way to find out is when the alarm goes off, disconnect the temp sensors in the cyl heads, if alarm continues its the alarm in the fuel delivery, could be clogged filter, tank relief hose clogged etc.

 

[ezeke]

Re: Over heat alarm after slow speed running

There's no fuel restriction alarm on the 140 looper, so overheat is the probable reason for the alarm.

The thermostats have vernatherms inside of the plastic cases and you can unscrew the covers and test the vernatherms in pan of water. Just put your kitchen thermometer in the pan with the vernatherms and watch as the heat rises. They should open at around 140 degrees.

The thermostat seats had multiple problems on the 140HP motors, so examine them carefully. If they are corroded, they will need to be replaced.

Also, be careful with the small hole in the thermostat cover gasket; if it is blocked the system won't work.