I cannot make up my mind whether to plug the bypass valve in the oil system or to leave in. Both engines are out of the boat now and I have been battling oil temp problems all along (3 yrs). To the point I have wiped out main bearings.
At one point last year I was going to do it, pulled one engine, removed the valve and tapped it for 1/2npt plug. Installed engine and fired it up. Due to an unrelated problem that occurred during the initial startup, I ended up pulling the engine again. Thoroughly disgusted about the whole deal I decided piss on it and bought a new stock filter adapter with the bypass valve, installed it and ran it the balance of the year.
My plan now is to install larger coolers (3X16) and replumb to eliminate elbows in the lube system. Was running stock mag coolers and plumbing.

Do you guys think I should just stay with the changes I have planned or go ahead and plug the bypass(s) anyway? If you say plug the bypass, is there a better way than tapping for 1/2npt? I was thinking of leaving the bypass in place and using a bolt and two nuts to affectively stop the valve from opening. Seems easy to do. Any thoughts on that? Looks like it would work and I could undo it later if necessary.

Engines are warmed over low compression 330hps making 400+hp with closed cooling systems. Oil Temps cruising have been 230 and at WOT there is apparently no ceiling to how high they will go. I am running high volume oil pumps.

Dave

thats not very hot for oil temp,280 isnt goin to kill it,the warmer the oil the more hp youll make,whats your engine temps?

Plug the block adaptor. You can run oil filters with a built-in bypass valve

I had a similar problem, where my pressure would start to drop after extended WOT passes. After speaking to a few people, we narrowed it to the cause to two things; water pressure/volume and the oil cooler. I purchased an Eddie Marine 3" HD and I had a guy open up the water pickup on my drive. Other causes that I am aware of are; not enough oil, too low of viscosity and worn out main bearings. Not sure if I answered your question, but hope I helped a little.

Offshore Addiction - Engine coolant temps are 155F cruising 165-170 at WOT blast

Sutphen - Mark IV and through the bravo 1 outdrive, standard height pickup.

Crazyhorse - Can I block using a 1/4-20 bolt and 2 nuts screwed into the back of the valve to stop the plunger from opening?

john.sblendorio - Flow is a concern as this is a closed cooling system. Never thought of opening the holes in the drive, good suggestion. I was hoping my new headers would have less restriction than the stock merc manifolds did, but that may not be a bottleneck. Did the 3" coolers fix your problem? I've tried new engines, all different oils and viscocities, no change.

Thanks for the help.

Dave

Sutphen30 - Where would I buy the convex washer and is it made just for this purpose? It is interesting you guys are keying in on the water pickup in the drives. I never thought of that. Wouldn't you think though if that was causing oil temp probs I would also be having issues with the coolant temp?

That is how I planned to replumb the lines, #10 with no elbows.

If I were doing a poll I'd say two of you voted for plugging the bypass and two voted for solving other ways. That still leaves me on the fence. Any more compelling reasons either way?

Dave

The more I think about the holes in the drive the more I am a believer. Because I run closed cooling, the engine will not get hot as fast as the oil because it is being cooled by the anti freeze system. The oil though is cooled by the raw water which will show a lack of flow quickly. Hmmm.....

Thanks

Let me know on the washers and thanks again!

Dave

The guys around here just tap the hole and use a pipe plug. Either way is going to get the job done.