Have a friend with twin 500EFIs. One was rebuild top to bottom this past winter, the other got a top end fresh. Now oil temp is 50+ degrees different, not off the charts but different. He is running in real cold water (Great Lakes) 52 degrees. Oil temps on hot engine runs 190 to 230 and climbing when running hard. Cool engine 150 to 180 running hard. Water temp is exactly the same, exactly. He is concerned that later in the year, doing runs on warming water will give him serious issues with hot oil. I don't want to debate how hot oil can get, just want these engines to match as they used to.

A while back I read something on here about a bypass that has to be reinstalled on marine engines where the engine block filter housing would be? I searched but can not find it. Can someone explain what this is? Is there a chance the builder left it out? Can it be installed with engine in the boat or is it internal?

Thanks

http://www.offshoreonly.com/forums/g...-hardware.html

The bypass you are referring to is a 30lb unit that replaces the 11 Lb many of the truck engines come with. If he has the two 11 lb bypass valves installed in the filter block on that one engine that could very well be the issue.

The proper way is to remove the middle bypass valve leaving it open, then either install a 30lb valve or placing a plug in the inboard hole closest to the pan rail side.

http://www.ebay.com/itm/390855596324

Installing the 30lb valve is my preference.

when the rebuild wes done was the origional bypass used and what kind of oil temp did he see before the rebuild?i would suggest checking the grounds at the dash and replacing the oil temp sending unit ,the oil temp might not be as hot as the gage sais it is.

That is good info, thank you.

Still wondering what a builder may have changed or left out however. The engine was rebuilt as stock, to match the other one.

Yeah what mike said would be the smartest approach, followed by the other suggestions contained in that link. Might as well start with the easy stuff first. Seems like quite a few here have had erroneous readings regarding high oil temps lately.

Borgi don't wan to beat a dead horse but i will still ask if i remove the 11lb valve and install the 30lb valve do i have to plug the inboard hole thanks rod

Not at all! You want to remove the center 11lb bypass all together. Then install a 30lb unit on the inboard hole. This will direct full oil to the filter pad/adapter, hence oil cooler. You will never overcome the 30lb valve in a healthy engine. It's an issue of what fits in there better really, and the bypass valve is a perfect fit and inexpensive.

So as you can see, plugging it (outboard hole) or installing the 30lb bypass valve, is all a matter of preference.

And to give credit where it's due, Smitty(arcticfriends) did a lot of testing to come up with all of this great info. It's crazy what a wrong bypass valve and improper oil line sizes etc can do to your oil temps. One last thing I will add to this, mark from MER Performace uses Schumman oil pumps, and recommended I try one. One of the cool features of these pumps is an external bypass(vs bypassing oil back down the oil pickup tube). I'm curious to see if this translates into decreased oil temps. In other forms of Motorsport this seems to be a common finding.

Are you noticing a difference in oil pressures between the two motors? I am curious about the pressures at idle, cruise, and WOT when the temperatures are different.

oil pressure is the same at all rpms/ temps

If pressures are exactly the same I'd think he has an indication issue.