Rebel_Heart

If my oil temp never gets over 180 and my water temp hardly goes above 120 will I have any problems? My relief valve is set to dump water at 12 psi at 5800. Most of my boating the psi never gets above 8 psi. Is this ok as long as my water temp stays where it is? Thanks.

sleek1

I'm just a "shade tree mechanic" but I thought water temp on a boat should be around 160 for a Merc I/O.

DrNautica

Actually, your oil temp should get to 212* (that's where oils are tested and rated.) If your oil never reaches the boiling point of water, any moisture present in the oil will never have a chance to evaporate out. Your water pressure seems low to me as well. For a typical I/O, water pressures in the low 20's should not be harmful. Most dump valves will be set to begin dumping between 18-25psi in my experience.

I can understand wanting to keep your operating temps very low if you are running a blower or high compression engine to minimize the occurance of preignition/detonation but water temps in the 140-160 range should be about ideal.

Grog

Rebel -

Stock Merc setups should climb nicely to 140-160 deg and level off. Crossover setups run cooler water temps and lower pressure(like you are seeing). It sounds like you are not running a t-stat. To me, blowing off water pressure at 12 psi seems too low. A 20+ psi setting is more like it. In any case, you water pressure seems really low, especially at 5800 rpm.
Like DrNautica said, you need to keep your oil temp above 212 to boil off condensation.
Are you running a stock Merc BBC? 5800 RPM does not sound stock unless you are terribly under propped.

..my 1/2 cents worth..

Greg

Back4More

As long as your cooking the moisture out of your oil I think your fine....BTW, what motors are they?

JJONES

Oil works best at normal running temp!If its not around 200+ or your motor may not last as long as it should!

mrhorsepower1

The oil temp is fine @ 180. A nice range I like to see under WOT for along time (20 minutes or more) is 190-230. Your right there. The water temp if the engines are N/A I would like to see abit higher, 140-145. As long as your not seeing condensation in the engine your still alright. In my opinion the water PSI is fine. Again, my range would be 10-15 PSI and no more. Whether you are SC or N/A that's what we set our boats up to run at.

waterbum

Is there a correlation between water pressure and water flow (volume)? Even with a low PSI, as long a alot of water is moving (keeping the temp down) would the operating environment still be "safe"? It seems in this case the water temp stays low - indicating alot of water is flowing to pull heat out of the engine.

If I had a choice of water pressure (20 -30 PSI) with a high water temp (over 180) or low water pressure (8 - 12 PSI) with low water temp (around 140) I think I would choose the latter. Does that make sense?

Nordicflame

Mercury Racing Bulletin 2001-01 clearly states block water pressure to be 20-30 lbs at WOT. No less.
(Merc sells a 25 lb blow off just for this reason; it works perfect)

Whipple specifies 30 lbs minimum many, many times in thier installation guides.

These may be some pretty reliable sources

Just some hopefully usefull info

Dave

Dave

Rebel_Heart

Thanks for all the replies. My engines are 540s and a gen 6 block with Dart Pro One heads. I guess, my concern is that I have heard many times that oil temp needs to be consistantly over 200 degrees. If so, I can't get it there. But as some have said - it wouldn't be a concern. I will change the oil every 20 hours as they are new engines.

My water temp never exceeds 130, even after a hard run. So, I don't think that a lower water pressure should be a factor. I was just checking to see if my rational was well founded? I don't want to cause damage to my $$$$ head work performed by Jim V.