One for the books?

[smokinjoeyy]

1971 85 HP Chrysler: just installed new water pump and it pumps great, in the barrel and in the river. Now the problem, at low speeds it pumps great but when I get up to plane it no longer pumps.

In the barrel I took off the prop and got the RPMs up to see if the impeller was slipping on the shaft, pumped good at the higher RPMs.
Can it be sucking air as the boat is moving? The shaft is the right length.

I just got this motor so I can't say if it did the same thing before.

 

[deejaycee_2000]

Re: One for the books?

check your thermostat ....

 

[smokinjoeyy]

Re: One for the books?

It has been removed.

 

[eurolarva]

Re: One for the books?

Does motor overheat at high rpms? My guess is all your water is going out the exhaust down the motor leg. Chryslers are like old men with bad prostates. They dont pee much.

 

[J.L.]

Re: One for the books?

If the motor is not overheating and this is just an observation of the water coming out of the thermstat relief holes in the back, this would be because at higher rpms more water pressure is made and you are opening pressure relief valve causing less restriction with water flow (especially with t-stat out), and its easier for more water to discharge elsewhere.
However, if your motor is overheating, you are either sucking air when water pump is not submerged in water(boat on plane and not in a barrell), or your housing is no good.
Most likeky you replaced the impeller only. These pumps use a poor design of cast aluminum housings and wear and pit easily. They do not have a long life normally and you should replace with a WP kit FK1033.
The other likely is that you may have installed the wear plate upside down. It is possible with this pump and very easy to do. Make sure you align the wear plate direction with the housing before you install it so that you don't have any gaps. Also you should make sure the seal from the housing to the water tube is the proper one. Fit it to the tube with the pump housing in your hand to check for a tight fit. A few different seals are available and I have seen the wrong seal in a new housing before.
Jerry

 

[smokinjoeyy]

Re: One for the books?

This engine doesn't have the *pee-hole* as most of the newer ones-1971- the water comes out about midway down the shaft and it pushes out about a six foot stream of water. I did get the RPMs in the barrel up as high as I did on the water and the volume of water increased along with the RPMs.
While on the water I never let it get to the overheat point and it was a visual thing. When I saw it not pumping I dropped it down to and idle to allow it to pump.

Is it possible that the water coming off the hull of the boat is causing too much air mixed with the water that it will cause the pump to not have enough water?

 

[eurolarva]

Re: One for the books?

The only way you are going to get air in there is if your prop is cavitating. Typically when a prop cavitates higher RPMs or surging happen because air has less friction then water. Try this. Run motor at high RPM and when you kick it down test the water coming out with your hand. It should be around 130 degrees. Hot enough to call it hot but not hot enough to burn. If water is very tepid I would not worry about it.

 

[J.L.]

Re: One for the books?

You need to take a physical temp check of the powerhead at the lake. It should be cool enough to touch with your hand at the top in front of the head area. be careful though. I like to scoop a hand full of water and splash on that area to look for boiling or steam. I believe what you are seeing is normal since the t stat is out.
Jerry

 

[smokinjoeyy]

Re: One for the books?

In RE: to the water temp. I did feel the water when it starts to pump after not pumping and it was real hot, not like it is normally.
I did however watch the level of water as the boat was moving and it appears to have a vast amount of air bubbles at the plate just above the prop. Much more than I've seen on any other boat.
Is there a way to correct this or is it just a bad marriage between boat and motor?

 

[ewbish]

Re: One for the books?

In RE: to the water temp. I did feel the water when it starts to pump after not pumping and it was real hot, not like it is normally.
I did however watch the level of water as the boat was moving and it appears to have a vast amount of air bubbles at the plate just above the prop. Much more than I've seen on any other boat.
Is there a way to correct this or is it just a bad marriage between boat and motor?

You sure you got the OB adjust right? If you have the OB tilted w/ the prop to close to the boat, it will plow and make the engine ride higher out of the water at speed. The motor should be pretty much straight up and down with the boat in the water.

 

[smokinjoeyy]

Re: One for the books?

That's the first thing I did, tried it in all positions. Made no difference.