1991 force 70 HP - overheating

[saunts]

I recently replaced the impeller in this motor but, it continues to overheat when run at SLOW speeds.
Hot "spray" comes out the 3 holes in the rear of the motor but, not a "constant flow" like I see
on most motors...... Is this normal ?
Is there anything I can do to improve water flow ? The lower unit feels Very warm to the touch.

 

[Jiggz]

Re: 1991 force 70 HP - overheating

You need to inspect the thermostat to make sure it is not clogged or even working. If you search for thermostat topic on this forum you will find many pictures showing your where it is located and how to inspect and test it.

 

[saunts]

Re: 1991 force 70 HP - overheating

You need to inspect the thermostat to make sure it is not clogged or even working. If you search for thermostat topic on this forum you will find many pictures showing your where it is located and how to inspect and test it.

I guess I have NO computer savvy..... I Cannot find that subject or any pictures.
How do I get there....LOL

Thanx

 

[Jiggz]

Re: 1991 force 70 HP - overheating

Try this which is a list of result for thermostat search.
http://forums.iboats.com/search.php?searchid=7772531

You want to focus on those with attachments to see a pic of the thermostat and its location.

 

[jerryjerry05]

Re: 1991 force 70 HP - overheating

When you removed the old impeller, did it come out in 1 piece?
What condition was the housing and wear plate?
You run in fresh or salt?(profile)
Check the thermo and check for corrosion.Pics?
If your running on the hose, the lower unit will get hot/warm as the exhaust runs through it.
When it's in the water it gets cooled by contact with the water.

 

[saunts]

Re: 1991 force 70 HP - overheating

When you removed the old impeller, did it come out in 1 piece?
What condition was the housing and wear plate?
You run in fresh or salt?(profile)
Check the thermo and check for corrosion.Pics?
If your running on the hose, the lower unit will get hot/warm as the exhaust runs through it.
When it's in the water it gets cooled by contact with the water.

Jerry, I had a marina do the job so I cannot answer those questions.
However, the lower unit gets very warm even when it is IN the water.
This leads me to believe I may have a bad thermostat and, it's not even
opening to let cooling occur. Will check this out. Still can't find any pics
of where thermostat is located. Is replacing it an "easy" job ? I have very
little mechanical experience. I run the boat in FRESH water only and, have
used it very little.

 

[saunts]

Re: 1991 force 70 HP - overheating

Jerry, I run the motor in fresh water only. Still cannot find any pics of location.
Thanks for the advise

 

[jerryjerry05]

Re: 1991 force 70 HP - overheating


Thermo is located at the top on the head above the spark plugs.
The funny shaped rectangular box.
The thermo wouldn't have anything to do with the lower unit getting hot.
The exhaust passes through it and exits through the prop.
Have you had this motor since new?
Where you located?
Overheat can be: a bad impeller.You ever start the motor without it being hooked to water?(even 15 seconds?)
Starting in a bucket,the impeller needs to be under water, or DEEP in a bucket.
2-4 inches over the cavitation plate.Low water pressure in the hose.
Or could be: the exhaust plate/cover could be clogged with sand/corrosion.
Or could be:the thermo.Pull it and test it.
I put a cup of water in the micro and heat it to a boil.
Then drop the thermo in and see if the spring contracts and opens the thermo.
If it opens,slowly add cool water and see if it closes right. Do this twice.