1994 Force 120 impeller/overheat alarm

[ggundersen3]

I have a 1994 Force 120. Bought it 2 years ago. It's on a Bayliner 185 Capri. No problems thus far except it did something odd when I fired it up on earmuffs and the garden hose turned on about 1/2 way yesterday for the first time since fall winterization and winter storage. It started after a few tries like normal, ran ok, I revved it a little, then let it idle, all was ok, water pump apparently working as "pee hole" was discharging water like normal. Then, after idling for a few minutes the overheat alarm went on. It never did that ever before. I of course turned the motor off. Let it sit for a while. Moved the earmuffs to the other side of the lower unit water intakes and turned water back on this time with faucet almost wide open. Restarted motor and the overheat alarm did not come after letting it idle for a while. What's going on?
Was the earmuffs just not enough volume of water to cool it properly? Or is something else bad. It always seemed just provide very limited amount of water discharge from pee hole when on the earmuffs compared to the gushing of water it discharges when on a lake.
Thoughts?

 

[jerryjerry05]

In the lake you have access to MILLLLIONS of gallons of water.
​The hose, on halfway is 2-maybe 10 gal a minute.
I think you figured it out. Not enough water.
Now since you might have scorched the impeller??? Replace it. Just in case.

 

[Jiggz]

It's not unusual at all to have high temp alarm while on muffs. The reason being is always misaligned muffs or not enough water pressure. If you have the water spigot wide open, there is a tendency for the muffs to drop off alignment from the water intakes due to high pressure. Additionally, with the motor vibration, the muffs can also fall off alignment from the water intakes. On the otherhand, if the water spigot is throttled back too much, the muff may stay aligned but then will not have enough pressure. Sure you'll see water flow from the exhaust and the pee hole but it may not be enough for cooling. The secret is to find the sweet spot for water pressure to maintain the muff's alignment with the intake and provide enough water pressure to maintain proper cooling.

Now there maybe something also that is going on outside of the norms and that is the impeller may have lost some of its pumping action due to missing fins. Hence, requires higher water pressure to keep the motor cooled. Of course, the only way to find out for sure is to test it submerged in a trash can or on the water at the lake. When was the last time you replaced the impeller?

 

[ggundersen3]

Bought it in fall of 2014, used it a lot last summer haven't changed it yet.

 

[Jiggz]

Time to change the impeller I believe. Typically, when one buys a used boat, regardless on what the sellers says about the impeller, a good practice is always to replace it (and this also goes with the LU gear oil). This gives the buyer two important information, the impeller is absolutely new and knows a good reference point or date when to replace it. Depending on usage, impellers are replaced on annual basis or every two years. Regardless of usage, impellers must be replaced every three years as its stated shelf life is that, three years.

 

[ggundersen3]

Thanks. I will get that done. Thanks again.

 

[ggundersen3]

So. On a '94 Force 120, how difficult is it to change the impeller? Should water pump be changed too? How difficult that? I've read some instructions here on other outboards. This is a 94 Force by Mecury however. Can I handle it? I've done other projects on past boats like carb rebuild and changing ignition from breaker to breakerless/solid state. But can I handle this? Some thoughts?

 

[SkiDad]

it's not hard just takes some time to get to lower unit off and on - see this link http://forums.iboats.com/forum/engi.../237589-step-by-step-impeller-change?t=231685

don't forget about the hidden bolt under snout and also take the shift pin out before you start so it doesn't get hung up on that - your 94 has the mercury style pump most likely which is a different size pump and impeller than the 80's models. Usually just the impeller is needed unless you see heavy scorring in the water pump housing. It helps if you can have someone turn the flywheel a small amount if you can't get the drive shaft into the engine when re-installing

 

[jerryjerry05]

Trouble reinstalling the lower unit:
Put the motor in forward before removing, then when reinstalling the lower,
​You leave the prop on and as you lift it up and it doesn't slide in you lift up on the right blade of the prop.
This turn the drive shaft and it will allow the splines to mesh.