Force not pumping water

Mikeypalone

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I have a 1988 50hp force with new water pump impeller,new thermostat but does not pump water when ran in a barrel. The shaft turns, the tube lines up. Took screw out of thermostat housing and can't seem to get water up there thus overheats after a few minutes and have to shut it down. Any ideas ? This is the second new impeller this week, the first was a 6 fin this one a ten fin. Any help is much needed.
 

Scott Danforth

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How high is the water in your barrel? Is it higher than the water pump?
 

Mikeypalone

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It is much higher than the water intake. Have blown air thru the system and don't find anything blocking it. The thermostat opens as it should but not getting water thru it.
 

Scott Danforth

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Did you make sure the drive key in the impeller is installed?
 

Mikeypalone

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Everything is back together as it should be to operate. I have the manual for this model and seems to be fairly simple system but I can't figure out what's going on. The pump housing has a few small pits but not bad for its age.
 

Scott Danforth

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Everything is back together as it should be to operate. I have the manual for this model and seems to be fairly simple system but I can't figure out what's going on. The pump housing has a few small pits but not bad for its age.

Any pits, nicks, etc is reason to change the whole pump, and not just the impeller
 

Mikeypalone

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I checked into that, to the tune of $269.00. Thought I would check on here first in case I was missing something simple. Can a wire be ran thru the thermostat cavity down thru the tube. It gets air thru it but I'm thinking if anything is in there it may restrict water flow. Yes, I'm grasping for straws but want to make sure before I proceed.
 

Nordin

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The water intake is lower than the pumphousing.
Remember that the impeller is not selfsucking, on a boat and in water the water level is much higher than the waterhousing when the pump starst to turn.
When the impellerpump has start to draw water it will deliver water even if the level goes lower then the pumphousing .

Before doing anything more try again in a bucket and be sure the waterlevel is higher than the impellerhousing.
 

Frank Acampora

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Since at higher speeds the pump acts as a cetrifucal pump. a few small scratches or a bit of corrosion is not a reason to replace the whole pump. Excessive corrosion, cracks, or other damage is a reason to replace. NO--because of the many turns in the water path, you can not pass a wire down from the thermostat. The BEST you can do is run a wire UP the water tube until it hits the block.

Six fin and ten fin--it doesn't matter. In fact. at low speeds, the six fin is a little more efficient because of the greater volume between fins.

Do you have the adapter from water tube to water pump in place? Are you certain the impeller drive key is in place? It is a little tight and sometimes the key will drop out of the shaft as you are trying to slide down the impeller.Sometimes it will end up in the water intake cavity.

When running in a barrel, water level must be a least up to the level of the lower unit mounting bolts.
 
Last edited:

oldboat1

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Want to be sure the intake in the l.u. isn't blocked with some debris (mud wasp nest or whatever).

Assuming there is no blockage found and the motor is assembled, you could pull out the thermostat and push some water down through the t.stat housing -- should exit out the exhaust housing (should get back flushing down the water tube as well). If the l.u. has been pulled, you can do a couple of things: I would first turn the shaft by hand to see if I could feel resistance from the impeller turning (possible installation issue like the key not in place and the impeller not turning with the shaft, as previously mentioned). You can also spin the shaft using a hand drill, l.u. in a bucket, water a little over the impeller housing -- pump should function.

Additionally, you can push water up the water tube to the powerhead if the l.u. is removed. With the t.stat removed, the water should come out of the t.stat opening. With the opening closed up, water should circulate around the head and down inside the leg -- out the exhaust port on the leg, and out the tell tale if you have one. When pumping water, don't need much pressure -- just enough to push water through the passages.

If you are running in salt water, you may have to remove the cylinder head and exhaust cover to remove corrosion.
 

tommarvin

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Nov 22, 2015
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I would get some muffs where water goes in both sides of lower unit for two reasons. First, when we bought our boat, we used a 30 gal tote because it was better to run the motor in, After 5min there was a huge oily mess that took me a half hour to clean up, I couldn't believe it, I thought this isn't going to work.
Second, we bought muffs ,the water goes in both sides. This eliminates any water height problems in the barrel or tote., or tank, less water waste..
Overheat is three things, impeller, get the correct impeller, Like was said above is keyway still in place, fins oriented for CM drive shaft, Did you test t-stat in hot water, or bad sensor, test in hot water,the motor WASN'T really overheating? If ok, we move on, make sure water tube is clear, run wire up tube, shine light up tube, pour lots of water down t-stat hole does it drain out water tube fast? Is plastic part on water pump housing where water tube goes in still in place or is it stuck on water tube like last overheat post, if water pump housing has the plastic adaptor in place for water tube to insert into, make sure the water tube goes into the plastic adaptor,when you install lower unit.
 

Mikeypalone

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Jan 29, 2016
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final update: took water jacket off and found lots of debris looked like some type of calcium build up. Cleaned everything very carefully and reassembled. Motor runs great so I installed telltale and took to the river. 3 hours running and all is well. I would like to thank everyone for the help and ideas.
 

tommarvin

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Just to be clear, I've never heard this before being the actual overheat problem. You took the head off cleaned all the calcium build up, and that was the cooling problem?
Good for you.
 

Mikeypalone

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I'm not a mechanic so my definitions may not be correct. The motor would not pump water, changed impeller still no water. Checked thermostat and replaced. Still no water. The motor is in a barrel with water level 12 inches above water intake. The alarm goes off within 2 minutes of starting motor. Took thermostat back out and housing is wet, decided to remove water jacket and found build up of deposits in a few places so cleaned it up and it ran fine. Pumps water great. Let sit for a day and started again, runs great. Took to river and ran great for 3 hours. While doing all this the overheat alarm would go off quickly with no water so I would shut it down quickly. So, I guess overheat may not be the correct term because I didn't let it run long enough to get hot. It would have overheated if not shut down. I did the telltale thing so as to keep an eye on water pumping and that works great. The water jacket was the last thing I did so I'm guessing there was enough restriction to not get enough cooling going on. I do know my overheat alarm works great. If your thinking something else was the problem please share your thoughts with me as I am wanting to learn all I can about this motor. Thanks
 

oldboat1

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That type of blockage in the passages will definitely cause overheating -- a very common issue with brackish or salt water motors, or anywhere the motor picks up debris or mud. (Tom -- bolts can break, so would want to be careful removing covers on your dad's motor, for example.) Regular flushing helps, but isn't a cure.

As a blockage was found under the exhaust cover, I would pull the head cover as well and clean under there -- if not already done. Would normally replace the head gasket too at that point (resurface cover and replace gasket). I wouldn't take it for granted that the overheat sensor is responding correctly, although it's wise to assume it's signaling an overheat condition. It would be a good idea to get a separate reading of head temp. Surface temp on top of the head shouldn't exceed 160F. (IR temp guns are cheap, and a good investment).
 

Mikeypalone

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I have an IR gun and after 30 minutes run time( on trailer in river) the temp was 146 degrees. That's just over idle I didn't want to take off trailer for now.
 

oldboat1

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Temps. between 140 and 160 are normal. Sometimes lower. Shouldn't be higher.
 
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