1975 15HP Evinrude Water Pump, I need a mechanic

[drivadesl]

I'm having issues with the above motor. Bought it recently, ran it off muffs, there was some water flow out the discharge on the lower unit, but didn't seem sufficient flow to me. Sort of a dribble at best even when revving. Discharge water was very warm. So I remove the lower unit, inspected all passageways looked clear. Inspected the impeller. Not warn, or cracked. Housing is solid. I install a water pump kit anyway thinking to start out on the right foot with this.

One thing I questioned was the impeller is mounted to the drive shaft, and the shaft has a flat on it where a round key sits, and mates with a round keyway on the impeller. Never saw this set up on other machinery, pulleys or electric motors. Used to seeing a flat key and keyway, not a round key and flat. The impeller sort of floats on the shaft radially, not fixed to the shaft. Does that sound right? It will rotate to the point where the round pin catches on the flat.

So I ran it, and not a drop of discharge out the lower unit. Ran it a little to test, then shut down, no overheating.

Not sure if the drive shaft is worn to a flat, and is causing poor performance or,I'm missing something else. Thermostat issue maybe?

Sorry for the long post. Any help from someone who can clear this up is appreciated.

 

[Daviet]

Re: 1975 15HP Evinrude Water Pump, I need a mechanic

Remove the thermostat and see if the flow picks up.

 

[Rick.]

Re: 1975 15HP Evinrude Water Pump, I need a mechanic

Sorry but I don't quite follow your description of the impeller key way connection. However it is it must lock the impeller to the drive shaft 100% or the drive shaft will just spin and the impeller won't. Perhaps a picture or, if your certain it's a good connection then so be it. A couple of things to check. Make sure the water tube sits well into the pump grommet. The grommet can pinch off the water flow. The other thing that is very important is to try the motor in a barrel with water well up the leg. If the leg isn't in the water enough it will cause a no flow situation. Muffs are not going to tell you the condition of the pump. Best of luck. Rick.

 

[JackHunter]

Re: 1975 15HP Evinrude Water Pump, I need a mechanic

One thing I questioned was the impeller is mounted to the drive shaft, and the shaft has a flat on it where a round key sits, and mates with a round keyway on the impeller.

That sounds right my 97 15hp is the same, have you tried to see if the water passages are clean? i somethimes have the same problem ( mud wasps getting into the cooling system after heavy rain)

mabey blow them out with an air compressor just take the L/U off so you dont blow any dirt into the pump

 

[drivadesl]

Re: 1975 15HP Evinrude Water Pump, I need a mechanic

Thanks for the excellent replies. Firstly I will try to test it again in a garbage can, maybe thats the problem from the start. But I have feeling I will be removing the pump impeller again, cause the keway/flat arrangement is bugging me. It definitly was not solidly fixed on the shaft, at least after I installed the new one. The old one, felt like it was so maybe its my install that is faulty. If I get to that point will take a photo to show what it looks like.

If it still isn't working, I will check the thermostat, In any case I will be pulling this apart again.

Beginning to think I should have spent the big bucks on a new one. Who has time to work on this stuff??

Thanks again, and I will reply on update.

 

[raczekp1]

Re: 1975 15HP Evinrude Water Pump, I need a mechanic

look at page http://www.sschapterpsa.com/ramblings/Ramblings.html
but i think the problem can be at termostat and upper water tube gromet.i would tear down powerhead and put new upper gromets and new termostat.
i think 3-4 hours of work, maybe less

 

[the machinist]

Re: 1975 15HP Evinrude Water Pump, I need a mechanic

The flat on the driveshaft is how the factory makes them. The round key slides to one side & gets bound up & wedged against the impeller's tapered inside. Their thought may have been it could be eaiser to install with the key being able to somewhat self align. When I first saw that I also questioned it. Mercury uses the same flat on their shaft, but they use a key that looks like a hat that fits better. You can buy a mercury key & cut the sides down to make it fit if it makes you feel better.

On your initial post you say there was some water flow out of the discharge at the lower unit. That bothers me as I do not understand, unless you are running it on muffs & have lots of city water pressure forcing water where it would not normally come out of (as I understand your post).

Does the block behind the flywheel get so hot that you can not hold your hand on it for 20 seconds or so or the paint there starts to burn? That seems to be the test if the engine is overheating. As Daviej says remove the thermostat cover (it is a chore on that motor, almost as easy to remove the head), check the water passage & the thermostat. If it may have been ran in saltwater, you could have debris build up in the head & cylinder cooling passages. And as a last (hardest to cure) is the water tube inlet & outlet at the bottom of the powerhead may need to be replaced. Again detailed in my "Ramblings".

Also on that motor (from 74-76) there is no tell tale water indicator, it is just a blubber hole on the upper rear exhaust housing that some water mixes with some exhaust gasses. For a true water flow condition go to my "Ramblings" where I describe how to install a tell tale (pee hole) on that motor. If after you modify bit to a true tell tale indicator, you can have a better understanding of your water flow.

 

[drivadesl]

Re: 1975 15HP Evinrude Water Pump, I need a mechanic

Thank you. I'm glad to hear from a few of you who have confirmed the shaft is not the issue.

I ran the engine in a large can filled to the top. Revved it up a bit, and it didn't take long for it to heat up to the point I didn't want to burn my hand on the block so I shut it down. Not one dribble out the exhaust. So will proceed to the thermostat and let you know what I find out.

Machinist, when running on muffs, I was referring to the water discharge openings that are just above and to the tear of the water intake slots on the lower unit. I got this from the Service manual, so I was looking for water to discharge at those openings.

Before I install a **** hole, I want to get this engine running right. On top of the cooling issue, it needs some tuning also.

Thanks again guys for the passing along of your knowledge and experience. AWESOME!

 

[Tim Frank]

Re: 1975 15HP Evinrude Water Pump, I need a mechanic

Beginning to think I should have spent the big bucks on a new one. Who has time to work on this stuff??

Or spent small bucks on a manual....