where to start?

[1fast6]

I have a 99 carbed mariner 200 that is having an overheat issue. Boat will run all day just off idle or on plane on glass. Once I hit moderate chop above 3,000 rpm it will set steady over heat alarm.
I don't know when the water pump was last changed so that is getting done regardless.
Could this be a cavitation problem? I have a water pressure gauge. Usually never gets above 5 or 6.
thanks for any help.

 

[j_martin]

Re: where to start?

Sounds like water pump is marginal. Also sounds like you might have the engine a little high, and it's sucking air in the water intake.

 

[1fast6]

Re: where to start?

That's what I was thinking but motor is trimmed all the way down. Only happens in rough sea. I am changing the water pump today so I will post the condition of the pump that I remove. I will sea test tomorrow.

 

[1fast6]

Re: where to start?

I think the pump looks pretty good. I have never seen one before to compare it to but I have been a mechanic for 20+ yrs.

 

[CharlieB]

Re: where to start?

Notice that 'groove' worn in a perfect circle around the hole in that plate?

That ain't 'factory'.

And I'd bet you will find that same groove worn in the upper stainless 'cup'.

Poor side seal on the impeller, as the gearcase rises in the water as the boat comes on plane, the top of the pump comes out of the water and begins sucking air.

Time for a pump rebuild kit.

 

[1fast6]

Re: where to start?

Notice that 'groove' worn in a perfect circle around the hole in that plate?

That ain't 'factory'.

And I'd bet you will find that same groove worn in the upper stainless 'cup'.

Poor side seal on the impeller, as the gearcase rises in the water as the boat comes on plane, the top of the pump comes out of the water and begins sucking air.

Time for a pump rebuild kit.

Thanks. Just ordered my kit today. Will be here tomorrow. When I removed the impellor the fins stayed curved they didn't straighten out. Is that bad?

 

[Wingedwheel]

Re: where to start?

That's typical of an old impeller.They lose flexibility and their seal. The new impeller will be nice and flexible.

 

[1fast6]

Re: where to start?

just to update. took boat out yesterday after changing impellor. Ran great maintained 5-6 psi and had good flow from tell tale at all speeds and water conditions.
Thanks for the help fellow iboater's.