Kanookstr

OK, this is wierd??? I took the procharged 502 Mag out of my old boat and put it into my new Sunsation about 25 hrs (of boating) ago.... Every thing is set up exactly the same as it was in my Stingray. It had 224 hrs when I pulled it out of the Stingray. Leak down and comp test was perfect!!! between 155-160 on all 8 cylinders.

The only thing different in the Sunsation is a sea strainer.
Well with my 120° stat, at 3500 rpm and above, I can watch my water temp go from 120° to 160° back and forth, back and forth?????
It does this every 15 seconds or so. It will climb from 120° to 160°
as fast as you can count 1-2-3-4-5, then it will go back down to 120° and start all over again after a few seconds???? I know 160° isn't high, but it shouldn't do that, and it never did.
I watched the sea strainer durring this, and it remains full, I also tried 2-3 new stats incase the one I bought wasn't good, So I know it isn't the stat????
It's just wierd????

Oh BTW I run a 120° stat..

GLH

Claude,
502 Mag MPI / I bought new thermostat's this spring and they mentioned that I should only use 160* therm in my 502 Mag MPI's... You say yours is a 120*???

Check PM also

Kanookstr

Don't forget I am super charged GLH... not the same animal
Most people run NO stat when Super charged, but with our climate, the water is to cold, and the oil gets foamy/frothy runing without a stat. So I run 120°.

Turbojack

Impeller going south? Too much or too little water pressure. I first thought too low pressure. I went to explain why I thought that & I then started thinking too high pressure. What is your water temp?

Kanookstr

Below 3500 rpm the water temp stays at a perfect 120°. the fluctuation starts at and above 3500rpm. Water pressure is between 13-17 psi at 3500 rpm, but when the temp climbs to 160° the water pressure drops accordingly to maybe 5 psi. (I blame this on the stat opening, thus releasing extra water).
at WOT my water pressure is about 28 psi, and then when the stat opens, she falls to about 17 psi. I first thought the Stat was getting shocked by cold water, but this is the way it was for 224 hrs prior to going into this boat, but theres nothing plumbed different, except for the new boat has a sea strainer. And I already watched that while this was happening, and it stays full.

BTW the reason I run a 120° stat, is because I am running a procharger.

GLH

Would trying a 140*state be out of line??? this is a $15 experiment.

GLH

Bad sender on t-stat? I'm sure you taugh of all that. mind you if water press fluctuate also something is happening inside the mill.

GLH

or even try it without t stats should resolve pressure fluctuation. just monitor temp.

Audiofn

Man that seems like really high water preasure to me. I do not think you really want to see much over 15 pounds ever??? I wonder if some how you are getting some steam pockets in there? I also had this happen once and for me it turned out to be a bad impeller.

Good luck

Jon

candyman35

What kind of water pickup do you have? Could you be running out of water and sucking air into the system? Can you see any air bubbles in the strainer? Did the old engine have the water pressure drop over 3500? On a hard turn did you ever notice the water pressure fluctuate?
Dan