VP 4.3GL 2000 - Overheat Diagnostics

[cmyers_uk]

VP 4.3GL PEFS - S/N 4012018114

Symptoms - above 1500 rpm overheat, 1500 rpm and below fine.

Ran the checks from the VP Diagnostic Guide. This is what I found

Idle - Pressure 2psi but did not register a vacuum on the guage
1500 rpm - Pressure 8 - 9 psi vacuum needle flickering between 0 - 3hg.

At this time there was no bubbles in output and 2 large bubbles in input that didnt appear to move. No water was coming out of the hoses to the exhaust manifolds.

At 3000 rpm the pressure went to 20psi then dropped to between 10 - 5 psi flickering like mad input 0 - 3hg flickering. The output looked white with bubbles and input didnt seem to have bubbles. Tiny dribble of water down hoses to the exhaust manifolds.

So my thoughts are

a) I dont have a clue
b) Seal to the impeller bad, impeller bad.
c) Blockage in the block.

Q: I cant understand how I have high pressure on the output with no vacuum from input?

Q: Should the hoses to the exhaust manifold always be full of water?


Tried to get new impellor and seal but not in stock. Have ordered one. New thermostat installed.

Any thoughts?

Regards

Chris

 

[Bondo]

Re: VP 4.3GL 2000 - Overheat Diagnostics

Tried to get new impellor and seal but not in stock.

Ayuh,....

Anytime there's an overheat issue, the impeller is the 1st thing to replace.....

 

[Don S]

Re: VP 4.3GL 2000 - Overheat Diagnostics

Q: I cant understand how I have high pressure on the output with no vacuum from input?

Very simple, the impeller vanes are probably permanently bent over. They must be flexable. Their bending over and straightening out is what makes the pump a pump. Even with a small amount of water flow from a worn pump can create pressure, just from all the restrictions in the system
I too am amazed you went thru all that testing without first replacing the impeller and inspecting the pump. As Bondo said, the FIRST thing you check in any overheat is the impeller.

 

[cmyers_uk]

Re: VP 4.3GL 2000 - Overheat Diagnostics

Guys, I am a bit stupid but perhaps not as stupid as you thing.

The minute I overheated on the water I stopped , took the impellor out and replaced with a spare I had in the boat. The old impellor looked in fine shape being only this seasons with no bent / missing / vanes , no cracking etc. The replacement was the previous years and had served me well with no issues. What I didnt replace was the o-ring. (Big mistake I know now!)

I am not near my boat, I live inland so when I went to the boat I went carrying the overheat guide from Don, the bits and bobs to test pressure , vacuum etc , the clear hose , new thermostat , gasket , but they were out of stock of the impellor. I assumed the local marina would have one but they didnt either so I did the tests anyway.

My main confusion until you told me was I had assumed that if I had high pressure then the pump was pumping well!

Even with a small amount of water flow from a worn pump can create pressure, just from all the restrictions in the system

Thanks for you help guys I have ordered from the web a new impellor and a new one for a spare.

So I have learnt two things 1) dont assume anything and 2) a worn pump can create pressure.

Thanks again for all the advice and docs. I will be back if the new impellor does not fix it!


1) last bit of advice greatly appreciated. The pipes going to the exhaust manifolds should they be full of water all the time, I am assuming yes?

Regards

Chris