Allan4

Blue Thunder ........HAHAHAHA

Waterfoul.....looks like you are finally catching on...

tomcat

Sean

Since you mentioned the low oil pressure problem, there is another possibility that has been discussed on OSO before. If these are GenV/VI blocks you need the high pressure oil bypass valves in the filter pad on the block. I had low oil pressure after a WOT run, but the oil temperature sender after the cooler hardly moved. I would have to fast idle for a few minutes to keep 20-25 psi otherwise it would drop to 5-10 psi like yours. After this cooling off period the pressure would come back. Pressure on cold start and at higher RPM was good.

What I found were 11 psi oil bypass valves instead of the 30 psi valves. This is okay in a car with the filter on the pad on the block, but when you use a remote filter, oil cooler, lines and fittings the extra restriction creates too much pressure at the bypass valve and it opens. The result is at WOT a lot of your oil bypasses both the filter and the cooler, temperatures go who knows how high and viscosity goes down. Come back to idle with this hot oil and you have no pressure. After the oil cools down, you have the pressure back. Sound familiar? This little vlave problem has ruined a lot of marine engines. It seems that when the GenV/VI blocks come down the production line, they all get 11 psi valves, and even the engine marinizers didn't pick up on it right away.

My oil temp sender is after the cooler, and the reason it hardly moves is only a small amount of the oil is actually taking that pathway and it is well cooled by a big oil cooler. Only the temporary oil pressure problem led me to look into the bypass valve. Scoggin-Dickey have a tech sheet that explains what you need to do. (806-798-4000).

While you're at it look at your oil lines and fittings and eliminate unnecessary elbows especially drilled 90s. I got rid of 3 drilled 90s with one sweeping line. If you follow the tech sheet you will remove the second bypass valve in the block (it's there for plumbing an oil cooler directly from the block, where you likely have your oil cooler in line with the remote filter). When you do this you eliminate another 3 drilled 90's. This will increase oil flow through the remote line and reduce the pressure at the bypass valve, so the 30 psi valve should never open. Some guys don't use the 30 psi valve, they just plug the hole, but hot dirty oil is better than no oil at all if the remote line should get plugged for some reason.

The bad news is, it's very difficult to change these valves without pulling the engines. Good luck!

formula31

Tomcat. Is it correct that none of this applies to a Mark 4? I know my stock Merc adaptor has a bypass valve in it. I wonder what pressure it is set at and if I am getting enough oil through the cooler and filter? My hot idle pressures are also pretty low, roughly 15 until things cool down after a few minutes.

jspeeddemon

A Mark 4 still has a oil filter bypass and but not the oil cooler line provision or the second bypass. Myself I plug the bypass because I eant all my oil to go the route of the cooler and filter, however there is debate. I change my oil several times a year along with the filter, so I've never had an issue with doing it this way.

BRUCE SEROFF

Im only reading 140. is that too cool????

blue thunder

I think it is, but depends on where your sender is located. If it is after the cooler, it may be ok. I've heard others say they think 140F is fine.

BT

26scarab

Mine is about 140-150 deg at a 3200rpm cruise and might get over 200 after a hard run. I don't have any condensation problems.
Also oil pressure is about 45lbs at 5800rpms and 25lbs at an idle warm. I'm not real happy with that but the motor has been apart twice (lifter problems) and after 160 hours the bearings looked great.

WETTE VETTE

I run my oil temp sender in the pan. This is going to be the hottest oil and that is what I want to see. I run a stock bypass and the oil only gets to 220 after a very long pass at 6300 RPM. The trick to using the stock bypass is line sizing and oil viscosity. Keep the lines -10 with few 90 degree fittings and run 10W40 or even 10W30 and nearly all of the oil will get filtered and cooled especially when oil temps hit 180 plus degrees. For most of our motors 10W30 is fine and for some of the real hot set ups 10W40 may be better. Unless you are racing any oil weight with a 50 wt attached to it is just robbing HP and straining parts. In my opinion if your oil is hitting 270 it better be synthetic. My .02.

Turbojack

When you replaced the impellors were parts missing? If so did you dig out the parts? Most times when a blade of an impellor rips off it goes in the line & is stoped at the first cooler after the water pump. Thus blocking water from flowing thru the cooler. Just remove hose at first cooler after pump & feel around. You may be surpised of the parts you find.

tomcat

Good point about picking lines and fittings to keep the pressure losses down. Your oil temp in the pan proves that it works even with the stock bypass. I wonder how much HP it takes to spin an oil pump?