94/95 Force 120 - Alarm = Impeller/Water Pump/Thermostat?

[kingstretch]

New (to me) boat. Just got at least partially through a fuel issue by replacing fuel lines, fuel filter, primer bulb, rebuilding fuel pump. That thread is here: 94/95 Force 120 - Fuel Problems.

So the boat actually runs at WOT now without bogging down on me, so that's definitely a good thing. I was heading down the lake today to try and get a feel for how it ran at WOT and suddenly an alarm came on. I remember reading one time that boats have temp alarms and low oil alarms and had the sense to throttle down and shut it off. Pretty sure since I'm premix, the issue is the temp alarm. I did some searching on here and found a lot of suggestions, so now I need help prioritizing.

For some added details, the boat will "cruise" pretty consistently, no alarm, no real issue. The alarm came on when I was running at WOT for a few minutes, and I didn't try it again just in case something was wrong. Anchored for a little while and then ran back to the dock at low speed. No issues. There is water coming out of what I thought was the pisser (2 holes just under the cover lever), but from what I've read on here, my motor probably doesn't have one of those and this is likely just pressure relief.

So from what I can tell, I'm probably looking at the thermostat, the impeller, and/or the water pump. Is there an order I should go with or just buy and replace them all? Are there any tests I should try and run to help steer me in the right direction? I've got a pretty decent collection of tools, but no specialty boat tools and no specialty gauges.

Thanks again for any help - I'm determined to get this thing up and running...

 

[gussbuster]

Re: 94/95 Force 120 - Alarm = Impeller/Water Pump/Thermostat?

if your getting water from the "pisser" holes, then your impeller is functioning....I cant say how good it is from here obviously but it is definitely working. If the boat is new to you, there is no telling how old the impeller is...probably a good idea to replace it regardless. Overheating at WOT could be a number of things. Im certainly no expert and maybe someone could back me up here, but I would think either there is a partial blockage in your inlet tube, or water jacket: the impeller is not pumping enough water to sufficiently cool, or maybe the carbs ar too lean wich would cause it to run hot. I would say impeller for sure and check carb adjustment for starters. They are pretty easy to do. Im not 100% sure, but it doesnt sound like a thermostat problem to me. I believe thermostats will usually fail "open" wich would cause a constant cool flow to the engine..someone else may be better equipt to answer that though. First thing I would do is buy a manual if you dont already have one.

 

[roscoe]

Re: 94/95 Force 120 - Alarm = Impeller/Water Pump/Thermostat?

A weak/old water pump impeller will lose pressure at wide open throttle.

Start by replacing the impeller.

If the inside of the pump housing looks scored and badly worn, replace the entire pump.

Thermostat is also a maintenance "consumable" item. You can test it by carefully removing it, trying not to damage the gaskets, placing it in a pan of water on the stove and slowly heating it, it should open at either 130 or 143*

 

[kingstretch]

Re: 94/95 Force 120 - Alarm = Impeller/Water Pump/Thermostat?

Thanks for the comments.

gussbuster - I read in one of the other threads on here that those holes were for pressure relief so I was thinking that might not be any sort of indicator that the water pump and or impeller were operating correctly, but I guess that water coming out still has to come from somewhere since it's pressurized. There doesn't seem to be any obvious blockage in the inlet, but it could be deeper than what I can see.

roscoe - I'll take your suggestion and start with the impeller. It doesn't look like there's much to it. Is there any way to test that the problem is fixed without putting it in the water and running it at WOT again? Want to make sure I don't cause any damage...

 

[kingstretch]

Re: 94/95 Force 120 - Alarm = Impeller/Water Pump/Thermostat?

Follow-up question: Should I get the impeller repair kit (which appears to come with an impeller and gaskets), or do I only need the new impeller?

 

[gussbuster]

Re: 94/95 Force 120 - Alarm = Impeller/Water Pump/Thermostat?

On a motor that you have no idea whats been done to it, I would do the whole kit..housing and all. Should be under 100 bucks. Of course you could pull the old one out first and inspect the housing. As roscoe said, any scoring or damage to the houing wall will impact performance/lifespan of an impeller. If it looks clean and undamaged, the impeller/gaskets should be fine. Make sure to note the rotation of the old impeller before removing it. Put it in the wrong way and you'll blow an impeller in the first few revolutions of the motor.....been there...it sucks!

 

[erikpn]

Re: 94/95 Force 120 - Alarm = Impeller/Water Pump/Thermostat?

It won't automatically fail if you put the impeller vanes facing the wrong direction. It's not good for it because it stresses the rubber. But doing it a few times won't hurt anything. It's only damaged when you change the direction, forcing the vanes to contort. Once it's already going in that direction, it will function normally. I've done it by turning the flywheel both clockwise and counter clockwise after putting in the impeller. At hand speeds especially, nothing bad came of it. What really damages the impeller is running your engine when it is out of the water, when water will not lube the impeller and friction and heat against the pump housing will wear it down significantly in just a few minutes.