Impeller Pump

[ClemsonDave]

This one has me, and my friends. 2003 SN with PCM GM. I replaced the impeller because the boat was overheating. The used impeller was bad, but I have seen worse. I pulled the pump housing out of the boat, but kept the mounting bracket attached (so it would not get put backwards).

With the new impeller in, I ran the boat for about 15 minutes and the temp was steady at 159. Today, I pull a skier 6 passes. When I get in the water for my set, the boat starts to overheat.

We pulled every hose and found no blockage. With the discharge hose off of the impeller pump, there is only a small amount of water coming out of the impeller pump. I double checked the new impeller and it is fine. The pump housing looks fine.

My dealer said that he has seen this before, the pump looks fine, but after replacing with a new one the problem went away. I just can't seam to grasp how it could be bad. There are no moving parts to speak of.

Anyone have ideas?

[Rick]

Check to see that the rubber impeller is still attached to the brass coupler. If it is slipping it will look good but will not pump under load. Also check to see you don't have an air leak in the strainer. Once again it will work well at idle but will suck air under load. Good Luck

[ClemsonDave]

We could not hear an air leak in the strainer. Any other way to test that? Maybe bypass the strainer?

[Mikeski]

The strainer on my 95SN was the source of so many problems I finally just bypassed it. I won't touch the strainer seal on my 2005 until it gets really full of junk, the seals on these things are tempermental.

[aaron]

As far as the waterstrainer is concerned, i have had a 93 SN, 94 Sport and never had to worry about them ( 6000+ hrs) when they were in a freshwater lake.Just twist open and throw away water and debris suspension.
My 2003 Super Air was fine for 500 hrs in the same lake but the moment the boat was used somewhere else, this time for the Asian Wakeboard Tour ( Phuket)in a pond by the sea ( fresh with alittle sea water) the strainer got coated with this greenish algae/ gelatine-like that caused an impeller meltdown.We had to literally brush the metal strainer to get the stuff off.

But what happened later is relevant.Since impeller meltdown happened mid event, i had to quickly change the impeller....hot engine/v-drive, everyone waiting and watching, got new impeller in and guess what, engine still runs too hot, checked to discover no water coming thru the pump as the risers were getting HOTTER and eventually found out i installed the wrong type impeller.......

I had afew in my store and thought the impellers for the Ford engined Nautiques were the same......

After i reinstalled the "proper" type impeller , temp was fine but things got bad again after 2 hrs of continuous running....we were not sure what to do. So we rested the boat for an hour and ran the final rounds in about another hr......no overheat issues.

On returning home, i got help from this forum and checked all cooling lines/hoses and found afew impeller bits at the thermostat housing and these bits were obviously impeding water flow.

So check all the cooling lines/hoses and esp the themostat housing.While u are at it, check that the thermostat is working by putting it into boiling water over a stove.

[aaron]

Also, to open the thermo housing, u will have to pry it open.Gasket will be gone,and when i reinstalled, i used liquid gasket sealant and boats now working fine.
The temp guage shd be at 161 when idling hot

[ClemsonDave]

Thanks for the ideas.

We completely removed the thermostat and still no flow.

The impeller is the exact number that is on the back of the pump plate.

The funky thing is we limited one of our tests to:
intake from bottom of boat - hoses/fittings/strainer to the impeller pump. We removed the hose on the output of the impeller pump. There is very little water coming out of the pump. There are no obstructions.

I am going to try to make a hose to elminate the strainer. If still no flow, it has to be the impeller pump, right? If I do get flow, it would have to be the strainer? Beyond that, I have no idea.

[richard]

Impeller Pump

I had test my new Sherwood raw water pump same your way, can see weak water out , so, when idle, I notice cooling is not enough, (the starboard side 3.5" rubber exhaust hose too hot),But as soon as speed up to over 1300rpm,it become strong out and cooling is ok. so I don't let the boat idle long time.this is a small problem of my SAN so far.

[ClemsonDave]

RE: Impeller Pump

I was using the wrong gasket for the impeller housing. I used the 'o' ring rather than the paper gasket. It certainly looked like it was making a good seal, but I guess not.

Thanks for all the thoughts!! It was driving me crazy.