Sea Strainres & Water Temps
 

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...

check the condition of your hoses to make sure they are not collapsing.....my fisrt thought was that its mounted too high if you say they are not filling up all the way. If they are mounted too high and you keep getting air in the system i can see how this would be happening because the engine would be creating steam pockets every so often.

One other thing (and maybe i read this wrong) but is this going on while you are in the water or running it on a hose? If running on a hose...i wouldnt worry about it till you get out on the lake and this happens.....most if not all garden hoses dont have enough capcity to supply the engine with enough water. Drilling the holes will help get rid of the steam pockets too.

All my hoses are that heavy duty hose I cant even smash it with visegrips. Yes , it is only happening on the trailer with earmuffs, but why would one of my motors not do it and the other has temp to rise and fall? I will be on the river this weekend for the real test. On my thermostat housing my gasket that goes around the top plate has the 1/4 inch hole bypass in it so that is the same as drilling a hole in the thermostat (right)?
My seastrainers are below the water line.

Could you guys give me a bit more information on drilling holes in the thermostat. What do they do, how large and how many? Also, where are they and why don't they come that way OEM?

Thanks,
Bruce...

excursion, have you checked the thermostat itself? maybe its going bad? maybe the wrong one is in there? Not sure about what teh 1/4" hole you are talking about on the by-pass offhand. I would take it to the lake and do a fullon test there before starting to rip anything appart.

Outlawntexas, I have heard different things about drilling holes.....the most common reply to drilling holes i have heard you drill 3 holes all spaced evenly from each other and each one is a 1/8" drill bit. I personaly have done only two 1/8" holes and it worked out good for me in the past. :)

Wally,
What are they doing for you? :confused:

I had a similar problem with my boat. It turns out the gasket on the strainer wasn't sealing right, and it was sucking air and the temp guage would bounce around like it is on yours.

I would check all hoses and connections and any place that air can enter into the system, including the flushing connection.

i was getting the temp spike like whats going on here but while i was running....i never did find out what the real cause was. (my theory was the first builder put the wrong head gaskets on and it didnt have the right coolant flow through the engine) I drilled the two holes and it solved all the spiking problems for me anyway........ran at a steady 150 no matter how i was driving it :)

You might want to check the hose on the outside of the boat from the bellhousing to the transom. It should be tucked in the groove wrapping around the bellows area. I have heard of the hose getting pushed up and out of the groove and when you turn to port or trim out the hose kinks slightly. When the seapump starts pulling water it can collapse the hose. It's a bigger problem with standoff boxes because the hose is more susceptible to water pushing it up after big air and tailing in.

Gary