7o hp Johnson overheating

P

Pipestone Kid

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Joined
Jul 20, 2011
Messages
6
I have a 1989 70 hp Johnson that has a strange overheating problem. My alarm went off and after investigation etc. I replaced the water pump. (complete kit) Yesterday I went 4 miles down the lake at 3/4 throttle with no problem. When I increased to full throttle, the alarm went off. (after about 1/2 mile) My conclusion is it is probably one of three things--faulty thermostat; faulty sensor; or could it possibly be that the VRO is not sending sufficient oil at full throttle? Any opinions/suggestions are most welcome and desired.
Thanks, Jim
 
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Daviet

Fleet Admiral
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Sep 24, 2008
Messages
8,958
Re: 7o hp Johnson overheating

Is your alarm on steady or does it pulse?
 
D

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: 7o hp Johnson overheating

Normally a steady alarm is an overheat indication. It could be a defective temp sensor. Is the engine still overheating, can you hold your hand on the cylinder head for 3-4 seconds or will it sizzle water if you drop some on the head?
 
P

Pipestone Kid

Cadet
Joined
Jul 20, 2011
Messages
6
Re: 7o hp Johnson overheating

Well, I think I have finally solved my problem. I changed the water pump-no luck. Flushed the system--no luck. switched over to pre-mix and eliminated the VRO--no luck. (Good idea, tho) Finally was able to get a new thermostat (redesigned) . Tested it today and so far so good--NO MORE ALARM. Thanks for the help and thanks to this site for steering me to the info on disconnecting the VRO.
 
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