Hot Oil temps---why????
 

Okay...my latest dilema is the port engine seems to be getting the oil pretty hot. I am running crossovers without thermostats and the water temps never really read...so they I would guess them to be about 120 degrees.

I recently replaced both oil coolers with 12 X 2 models and the stbd engine also has the powersteering cooler. The stbd engine just barely hits 200 degrees when running 4000rpms, while the port goes to 230 after about 7 minutes of running. I switched the guages just to be sure it wasn't the guage. The block was boiled out as well...

Why would the stbd engine be running so cool and the port engine be gettin so hot???

What about the gauge senders? Try swapping those.

I knew someone would say that! Where should the sender be taking the temps from...the block or the remote oil filter?

Not that, but swap the sensors between engines. Just want to make sure that you have two matched temp senders. If you see the temps reverse, you know where the problem is.

Can't help with your problem but did you get any runs in, speeds?

I'd be more concerned with the 200* temp engine than the 230* engine. Both of mine run at 230* all day long at 3500. Go to 240 with a WOT blast, then quickly back to 230. 3000rpm gets me about 220. I always believe the best temp to be between 220 and 230 at cruise speed. Just enough temp to keep the oil "water free".

BT :cool:

SEAN, try switching either senders or even the wires for the senders on the engines. then see if port engine is still the hot one. seems mine has always been the starboard engine that runs 20 degrees more, never figured out why, just lived with it.
dave

I'll try switching the senders.

Do you guys agree that 230 is okay?

I always thought it seemed too hot, but blue thunder makes an intersting point...it needs to be hot enough to boil off any condensation that may form...

Dennis Moore says 220-270 is ideal oil temp.

I would agree with biggus if the 270 is after a wot blast and the 220 is seen at an easy cruise speed. 270 at cruise speed will be 320 at WOT. Oil can't take that.

I would think about trying a little heavier oil in the engine running 200 to see if that bring the temp up a little.

BT :cool:

Kool...now I don't feel so bad.

Thanks for the info...BTW, who is Dennis Moore?

Dennis is the author of Big Block Marine Performance.

It is the best book out there as far as building a BBC boat engine.

He also wrote the bible on small block power.

Kurt.

No one has mentioned low water pressure. The two of these combined (high oil temp and low water pressure) would mean either an impellar going bad or a clogged water line somewhere (probably from the impellar going bad as well). I'd look there if you are still having issues.

Oh, by the way, 210* is probably hot enough to boil off condensation.......270* seems pretty damn hot, but D. Moore knows more than I do.......:D

That must be "new math" Allan4.... I always thought the boiling point of water was 212. :D .... I agree tho... the oil temp is probably above 212 up stream of the sender when the guage reads 210... meaning of course, allan4 is correct in reality.

BT :cool:

I would agree with Allan4 (did I just say that??) about the water pressure. If the sender swap doesn't shed any light, start looking at the water system. And I also agree that 200 is too cool. Mine runs at 215-220 at 3500 rpm cruise, 230-235 at WOT blasts. Never goes above 240, even after several minutes of WOT running.....like chasing Rambunctious last Wed. on our JCI Poker Run. What a blast. Then again, the water was only 55 degrees that day. Brrrrrrr!!!!!!!!

Ohhh...that Dennis Moore...I thought you were talking about the other Dennis Moore:D :D :D

I just replaced both pumps, so I don't think that is the problem, so I'll look into swapping the senders.

Where do you guys have the sender located?

Thanks again guys!

My senders are mounted in the remote filter housing. After a really hard run I`ll see 260* before the oil goes through the cooler.

Biggus...I never really realized that the temp was taken before the cooler, so that is another plus...

How about the oil pressure after the hard runs?

The reason I am asking so many questions is because this 540 had bearing failure and I thought is was due to the hot oil and low pressure...you see after a 230-250* romp, the oil pressure would go to about 5-10lbs when I dropped it to an idle...it got progressively worse until 2 bearings failed.

Now it seems that it will still get just as hot, but I haven't run it hard enough or long enough to see where the pressure is going to go...the goos news so far is that th minute I drop it down to idle speeds, the oil temp immediately drops...before, it kinda hung out up in the 240 range for a while...

I really don't want to be replacing another motor anytime soon.:mad:

I`m not running any thermostats, oil or water. When cold, I`ll have almost 80 lbs and I do not rev it past 3500-3800 until the oil temp gets to 200* after the oil is up to temp the pressures will be around 40* at idle and 60* wot.

Good luck,
Kurt.

Blue Thunder ........HAHAHAHA:D

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

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!

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.

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.

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

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 :cool:

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.

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.

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.

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?

Older thread
 

Someone dug this one up from a while ago..............

Another thing to look at is yout oil level...............if it's too high the crank hits it, and it gets hot & foams.

I had this happen to one engine...............level looked good on the trailer, but was a bit high in the water cause of how the boat sat.

Just a thought

Wette Vette,
The bypass/dumpvalve you use after your pump will help lower temps. More water is passing through the cooler without forcing its way through the block and exhaust. Is that reasonable?

BadDog,
That is a reasonable assumption, but I haven't tested it out to see if it actually makes a differance. I suppose the dump could also be installed before the cooler and less water will be flowing through the cooler. It is my opinion that there would be no difference in the actual oil temps.

I ask because I just installed a dump valve on the downstream side of my oil cooler and my oil temps are a few degrees cooler than before. The seawater pump has to be flowing more volume to feed the bypass and block. I will post when I have more results. Previous oil temps were 200 at cruise and 220 at WOT. Never varied in any water temps. Eddie Marine cooler. By the way, what size and how many holes do you run in your t-stat? I have three 5/32 holes and could not get the block temp up in 55 degree water. Using Stainless marine crossover. Oil was OK.

I run the 142 t-stat that came with the crossover. I didn't modify it and the water temps hold at around 150 once warmed up regardless of water temp or if I am idleing or running WOT.