I installed a KPM water pump at the end of last season with a new stern mounted water pickup (both from Trick). I am overheating at idle but as soon as RM kick up to 1200-1300 or so the tstat opens and the temp drops fairly quick. When the motor is returned to idle the tstat will remain open for the duration of the run. Is the pump not making enough pressure to "pop" the tstat when it gets hot? This is a new Merc tstat and housing and it seems to function normally except after startup....Motor is a GM 350 marine vortec carb installed last year 10 hours or so.
Ken

Which water pump did u install? Is it the rebuild kit that puts a new housing on the back of the Merc snout? When I talked to KPM about ins and outs.. he said that on that pump.. you can hook it up backwards and it will still pump water, but not near as much if it is connected correctly..

I hope this helps..
Dick

Could be as simple as going to a smaller pulley to speed the pump up, Merc uses two different pulleys one for SB and one for BB. I tried the BB pulley on my setup at idle it ran so much water through that I changed to the bigger small block pulley before the bay testing.

How would I know if it is pumping backwards? The one pictured is the one I have (rebuild kit) but it seems to pump plenty above 1500 rpm or at least the water pressure is pushing enought water through..... MOP what size pulley are you using on the water pump?

klmken,
If you look at the back of the pump.. it sorta shaped like a "V". If you look at my photo my pump is mounted with the open end of the "V" away from the engine block... I< ... like this ... that makes the top port the input and the bottom the output.. according to KPM.. I would was surprised to hear him say that it will pump in both directions.. only good water flow in the one direction.. I was stabbing in the dark.. hoping that it would be something easy.. My pump is on a BBC and I have no problems with flow at an idle.. actually better than the stock pump housing..

Dick

Hi Guys;
Never come across this one before. I will try to become methodical with the info I have.

1) The stat should not need pressure from the water to operate and open and close. Please check the stat, by putting in cold water and boiling water. look to see if there is any sticking at all. From what you are describing it sounds that this may be the problem.
2)The pumps can pump both ways but with limited pressure on one side. We have now engraved the inputs on the body.
3) The smaller pulley will help since , and your pump will run the most efficiently at 1:1.

I am not sure how your system it plumbed but if you email me your phone number I will be pleased to talk through the system with you. And solve your problem.
Best regards Jules

Ps we are writting a new web site with full layout schematics and trouble shooting guides. We have also included photographic maitenance and fitting methods. we hope to eventually have these on video with our run dry tests and manufacturing . This has turned into a bit of a monster but it will be worth it.

Looks as though I am plumbed backwards. I have the big part of the "v" away from the engine and the intake on top. I am going down to the marina today to drag the boat home so I will swap hoses and see if this makes a difference. I will post a picture tomorrow.
Jules,
Thanks for the info. I'll send a pm if I don't solve this afternoon.

Klmken...

I think I mixed you up... the open part of the "V" is facing away from my engine block and the top is the input. That is what I tried to depict with the " I< " image.. the "I" being the engine and the " < " being the pump..

Does that make sense.. I wish I had a better pic of it..

Dick

I will get a pic of mine tomorrow and compare.