force 120 overheating

[byronjacobson]

HI,
I have a force 120 which overheats whenever i troll slowly with the boat and the alarm sounds. I change the impeller and this helps for about 6 months and then the problem returns. It doesn't seem to me that the impeller should have to be changed every 6 months. Any ideas to help me?
Byron Jacobson

 

[byronjacobson]

Re: force 120 overheating

this is an update on my earlier question. I unplugged the small plastic plug on top of the engine and the impeller was pumping water thru this opening. I also removed the thermostat, put it in hot water, and the thermostat does open at 130 degrees

If i let the motor idle at a slow speed with the plastic plug removed, the motor does not overhead. if i put the plug back in, then the motor will run hot at slow speeds. I've read where i can install a new plug with a barb connecting to a hose to show the water is pumping. I'm wondering if I have an air pocket or something that causes the impeller to work less effectively when the top plug is in, causing no water to reach the impeller which keeps it closed.

do i dare simply replace the plastic plug with a drain plug to a hose and hope it works? I've replaced the impeller each year and this same problem occurs about 6 months later. Your ideas would be appreciated.

 

[Stachi]

Re: force 120 overheating

this is an update on my earlier question. I unplugged the small plastic plug on top of the engine and the impeller was pumping water thru this opening. I also removed the thermostat, put it in hot water, and the thermostat does open at 130 degrees

If i let the motor idle at a slow speed with the plastic plug removed, the motor does not overhead. if i put the plug back in, then the motor will run hot at slow speeds. I've read where i can install a new plug with a barb connecting to a hose to show the water is pumping. I'm wondering if I have an air pocket or something that causes the impeller to work less effectively when the top plug is in, causing no water to reach the impeller which keeps it closed.

do i dare simply replace the plastic plug with a drain plug to a hose and hope it works? I've replaced the impeller each year and this same problem occurs about 6 months later. Your ideas would be appreciated.

I would think installing a tell tale would be a good idea.....an air pocket is something I have read in a post here someplace...regardless....a tell tale will let you know if your intake ports have gotten clogged by debris...

 

[Stachi]

Re: force 120 overheating

by the way...what does the impellor look like when you change it ?

 

[byronjacobson]

Re: force 120 overheating

this afternoon i installed a tell tale with a 4 foot rubber hose. it does sbow water coming out of the hose but it seems to be a weak stream when the boat is idling slowly. It did prevent the horn from blowing. took some temp reading with a temp tool and the temps close to the 4 plugs showed about 150, 155, 160, 165 going from the top plug to the bottom plug.
this week i'm going to install a new impeller and also replace the thermostat. I wondering if the impeller housing has some wear and tear that prevents good water pressure making its way to the top of the block. I think installing the tell tale allows air to escape from the top making it easier for the pump to push water. Anyway, if you have any other ideas would like to hear them.
Usually when i replace the impeller , the old one usually looks pretty good to me.

 

[Smokepole27]

Re: force 120 overheating

Just a guess when your at a slow idle water isnt being forced into the inlets, is the water pump submurged when at a slow idle? Possibly the motor is to high? or if you have it is the nylon insert that goes into the houseing making good connection could you possibly be losing water and not creating enough pressure at a low idle?
The telltale is a good idea but if yours is like my 85 then there is 2 ports on the back of the bottom call that would allow water to come out which would keep you primed. I added a telltale also because I want to see that I am pumping water when running
Ryan

 

[Stachi]

Re: force 120 overheating

this afternoon i installed a tell tale with a 4 foot rubber hose. it does sbow water coming out of the hose but it seems to be a weak stream when the boat is idling slowly. It did prevent the horn from blowing. took some temp reading with a temp tool and the temps close to the 4 plugs showed about 150, 155, 160, 165 going from the top plug to the bottom plug.
this week i'm going to install a new impeller and also replace the thermostat. I wondering if the impeller housing has some wear and tear that prevents good water pressure making its way to the top of the block. I think installing the tell tale allows air to escape from the top making it easier for the pump to push water. Anyway, if you have any other ideas would like to hear them.
Usually when i replace the impeller , the old one usually looks pretty good to me.

I recently replaced the water pump housing and impellor on my '89 125....when I removed the housing ,I found that many areas of the casting below the plate had 'vanished' ....I built up the passage walls with a few coats of JB weld , and flat filed it so the mating surfaces actually would mate again...I then smoothed out the passages with my Dremel....I sure hope it works !!!

 

[byronjacobson]

Re: force 120 overheating

today i went fishing to check out the motor again. I removed the thermostat to see if that would make any difference. the alarm went off again after trolling slowly. if i speed up then the water flow is enough to cool off the engine. if i idle slow, i notice the flow thru the tell tale is intermittent.
tomorrow i'm dropping the lower unit to check out the impeller and housing. the local marine dealer says they normally just replace the impeller. they also suggested to back flush. I'm going to try run my garden hose back thru the thermostat opening to see if that does any good.
i'm hoping replacing just the impeller does the job, because i might have to wait a few weeks to get the other impeller housing parts and I don't want to be without the boat for that long.

 

[pnwboat]

Re: force 120 overheating

You might also want to check the water passages in the exhaust cover. The water flows from the water pump to the water jacket at the bottom of the exhaust cover. From there it flows up the exhaust cover, then into the water jacket in the block. The water passages in the exhaust cover are small and are easily clogged if you've picked up some sand or other debris.

 

[byronjacobson]

Re: force 120 overheating

replaced the impeller today and now i have flow thru the tell tale even when it is idling at a slow speed. still surprises me that i have to replace the impeller allmost yearly to get it to work.

i also am finding it is hard to find good diagrams or parts for force outboards. anyway now for the time being I,m good to go. thanks to those who sent ideas. I still am wondering if their should have been some kind of rubber seal that would be located at the top of the plastic housing that would go around the drive shaft. I'm suspicious it has a missing part but can't find a good diagram to tell.

 

[TYLER HUNN]

Re: force 120 overheating

LOOK AT MY POST. Click on my name. Umm i didnt read the replys but you might want to do just a major cleaning and tune up. check the haed gasket, check compression, check to make sure that your exhaust isnt built up with carbon rez. check passages from impeller to head. its easy just inspect everything. this is a very simple engine

 

[Smokepole27]

Re: force 120 overheating

replaced the impeller today and now i have flow thru the tell tale even when it is idling at a slow speed. still surprises me that i have to replace the impeller allmost yearly to get it to work.

i also am finding it is hard to find good diagrams or parts for force outboards. anyway now for the time being I,m good to go. thanks to those who sent ideas. I still am wondering if their should have been some kind of rubber seal that would be located at the top of the plastic housing that would go around the drive shaft. I'm suspicious it has a missing part but can't find a good diagram to tell.

If you have a 2 piece drive shaft then you are supposed to have a rubberized seal that goes over the shaft like an O ring down to the pump houseing

 

[moparman]

Re: force 120 overheating

With this many water pump replacements ,you might want to check and make sure you don't have another problem that's hiding . By this ,I mean if it's running lean and as the water pump wears slightly[not pumping as much as new ],the lean problem comes in to play at idle. A look at the plugs will tell some what,but with alcohol in the fuel now days it's very tricky to read plugs like the old days. You might want to get some one who knows how to read plugs to help you on this ,but I think it's worth looking at. It's hard to believe that pumps won't last longer than 6 months, so check out your fuel system too[ it helps cool the motor to a certain extent]. Just my two cents worth

 

[srimes]

Re: force 120 overheating

why would running lean stop water from flowing out the telltale?