'92 2-cycle, 3 cylinder Johnson 60 HP overheat?

[imported_Walleye1]

Recently started experiencing problem and would like to hear your ideas before I take boat/motor to mechanic.

Motor starts fine, water flowing out of tell tale in good steady stream at all speeds. Motor readlines at about 6000 RPM, I have never exceeded 3800. Equiped with a sensor which sounds a a continuous horn when overheat condition detected, automatically dropping RPM's to about 2500.

Recently in 3200 - 3400 RPM, after going about 500 yards overheat horn sounds, water coming out of tell tale fine. Immediately stop engine, sit maybe 5-10 seconds, engine starts right back up, and run again. At that point, I take it easy and run 2,000 - 3,000 RPM with no more overheat horn sounding and no problems.

This has happened the last 3 times I have taken the boat out.

Your ideas on what to check first appreciated. Was told by a non-mechanic that he experienced an overheat condition with a different motor due to a loose plug and timing being off. You will probably laugh at me but I haven't changed my plugs for two years because I haven't experienced any problems starting or running until now. Water pump/impeller changed within past 2 years and seems to be pumping fine. Thanks.

 

[Joe Reeves]

Re: '92 2-cycle, 3 cylinder Johnson 60 HP overheat?

If the top rated rpm of that engine is 6000, it would be a good idea to exceed that rpm figure you mention of 3800 to "blow" the engine out occasionally.

Your explanation indicates a faulty/weak water pump. That tell tale outlet stream may look strong BUT......! The only way to tell for sure is to drop the lower unit to visually inspect it.

If the water pump proves to be okay, I'd strongly suspect a sticking thermostat.

 

[rickdb1boat]

Re: '92 2-cycle, 3 cylinder Johnson 60 HP overheat?

And it's super easy to check the stat. Just remove the t-stat cover (4 bolts) on the back and pull it out. Drop it in a pan with enough water to cover it and heat it up. See if it opens...If not, replace it. They are so cheap, I would do that first before taking it in...Below is a pic of the cover:

 

[imported_Walleye1]

Re: '92 2-cycle, 3 cylinder Johnson 60 HP overheat?

If the top rated rpm of that engine is 6000, it would be a good idea to exceed that rpm figure you mention of 3800 to "blow" the engine out occasionally.

Your explanation indicates a faulty/weak water pump. That tell tale outlet stream may look strong BUT......! The only way to tell for sure is to drop the lower unit to visually inspect it.

If the water pump proves to be okay, I'd strongly suspect a sticking thermostat.

 

[imported_Walleye1]

Re: '92 2-cycle, 3 cylinder Johnson 60 HP overheat?

Thanks for your thoughts on the problem Joe!

 

[imported_Walleye1]

Re: '92 2-cycle, 3 cylinder Johnson 60 HP overheat?

Thanks for the info Rick!

 

[mikesea]

Re: '92 2-cycle, 3 cylinder Johnson 60 HP overheat?

you should try and change the impeller at least once a yr.and lack of use is not a plus.the impellers tend to take shape of the cup they are pushed into,after time they lose alot of their affect,the volume can go down,salt and sand add to the problem,you also give the lower unit mounting bolts excercise too,they can be a big labor problem if they get stuck or break,use anti seize compound when re-installing parts,

 

[seahorse5]

Re: '92 2-cycle, 3 cylinder Johnson 60 HP overheat?

There were a few service bulletins about that motor back in its day for occasional overheating. You will have to find a dealer who is familiar with those engines.

Has the water telltale hose been relocated to the top of the exhaust side of the block, instead of at the lower side of the block?

Is the temp sender wire a tan with a blue stripe, or just solid tan?

The factory waterpump kit is a heavy duty design that also includes a new thermostat spring and gasket that should be installed.

Replacing the t'stat should be done on that old a motor, don't even worry about testing it.

Some saltwater motors or ones in muddy waters can get get deposits built up inside the cylinderhead which restrict water flow and cause a hot spot near the temp sender.