I have a problem with water temps, rising and falling very rapid. I have HP500's both are plumbed the same way, changed both water impeller's and thermostats, one motor starts and temp goes straight to about 150-160 and remains stable. The other motor goes to 150 and then back to 100 to 120 to 150 to 160 to 100 and so on. If I take the sea strainer out of the line and direct from the inlet it does not do it as bad or as much swing in temp. With the strainer in line, after about 15 mins of running on the hose it will stablelize at 150-160 only if the motor is reved up to 1500rpm when let of back to 850rpm the temp drops very rapid to 100-110 and the second I crack the throttle to 1500rpm it goes right back to 150-160 and stays.
The strainer never fills up just at the bottom and swirls around.
Could there be air in the line or the receculating pump not working??

Have you checked the pickup and hose for debris?

Yes, back flushed the system and clean.

some one figure this out , please

funny you say that... I just bought new strainer caps/gaskets and new impellar kits -- trying to figure out the exact same thing on my 500 efi's.

Gotta love OSO!

P.S. I'll update my post after installing everything.

I hope you have better luck in finding the problem than I have, I think I have stumped the board with this problem. I have been chasing this problem for about 3 weeks now. Keep me in touch with your progress.

hey james had that problem with my 25 hp500 i changed the circulating pump and temp stayed at 160.
the impellar in the pump was bad from salt water.

32 thunder rick

ps keep me posted about the poker run.

Drill some holes in the thermostat.

Hey Joe keep me informed on what happens.
I was leaning towards the ciculacting pump also Rick will swap between motors and see if the problem follows.
I have swapped the entire thermostat housing and did not help so The hole in the thermostat would not help.
Am trying to get to the water this weekend if the river will stop flooding.

I understand the pump problem but why would the temperature be affected by the sea strainers? Could it be that they are mounted too high. Are they at or below water level?

I am curious because I just installed 2 in my 342 and there is no freakin way I could get them between the stringers, so they are mounted to the sides and above the stringers under the gunwhales. There is a lot of hose going to and from them. I haven't tried them yet so I'd appreciate any insight you guys might have.

Thanks,
Bruce...