1990 CV40ELD Overheat Alarm at plane

[D_MON]

Overheat alarm sounds after running on plane for a few minutes, stops within seconds on idling engine. Tell-tale water stream is strong and cold, cylinder head is warm to touch, I can readily keep my hand on it.

Replaced thermostat, temperature sensor and rebuilt water pump with no improvement.

Boat is a 1980 16 ft Atlantic Boats well skiff with a 22" transom.

There are (at least) two paths to trouble shoot:

1) With a 22" transom, it is possible that the cooling system is starved when the boat rises on plane.

2) There is a blockage or leakage in the water cooling path.

What steps would you recommend to trouble shoot to root cause?

 

[99yam40]

Re: 1990 CV40ELD Overheat Alarm at plane

My bet would be on the motor being too high when at speed.
Is it on a jack plate where you can raise and lower it while running?

 

[D_MON]

Re: 1990 CV40ELD Overheat Alarm at plane

My bet would be on the motor being too high when at speed.
Is it on a jack plate where you can raise and lower it while running?

The motor is mounted directly to the motor mount transom at the front of the narrow motor well 39" in front of the stern transom. There is little room for a jack plate, but I could cut the transom down by 2". The current mounting arrangement means that there are two geometric factors working to lift the the water intake; the additional motor transom height and the lifting of the motor transom when the boat planes on the stern transom 39" behind the motor mount. This unusual well skiff was designed by Alton Ray Stapleford in Kinson for fishing and performs very well on fast trolling speed. My other option is to live with that!

 

[99yam40]

Re: 1990 CV40ELD Overheat Alarm at plane

They make manual jack plates also to adjust motors, may not take up much room.
Maybe a X 25" shaft is needed for that boat instead of the L 20"

 

[D_MON]

Re: 1990 CV40ELD Overheat Alarm at plane

I will certainly investigate the manual jack plate as a solution. Thank you for your help.