1997 502mpi motors. I have warm water in the bilge and cannot figure out where it is coming from. The port motor pressure gauge hold steady at over 35mph but the starboard Guage will bounce between 30 and 15lbs. If the water was cold then I would say I have a leak but again it is warm so I believe it is from the one motor but I can't locate it. So I have 2 questions does anybody have any suggestions and can I pressurize the motor when the boat is on the trailer?
I have run the motors on the hose in the driveway but can't seem to find any thing and when on the water at lower speed or idle I see no water coming from anything. Any help would be appreciated.

Any chance one of the drain petcocks is leaking?

If you are asking about the ones in the exhaust manifolds I just changed the exhaust system last year to stainless marine thinking the stock cast iron manifolds had a crack in them but I still have the same amount of water coming in. Is there other drains I am not seeing?

dont know where you are located but did the blocks get winterized properly ? being warm its aft of the sea pump, there should be block drains both sides just above the pan rail, oil & ps coolers should have drains also

I would say the winterizing is fine because the motors run strong and I have no other issues. Also the water really seems to accumulate faster at higher speeds. Also the water pressure gauge bounces only at higher ram. Almost like there is a pressure relief somewhere.At idle or low rpms it seems like no water is coming in to the bilge.
Do you have any thoughts on how to pressurize the system? I was thinking about hooking up a low pressure pump to the engine flush to see if that would show the leak.

Leaking circulation pump? Lose hose clamp?

I just put 2 new sea pumps on to eliminate that problem and I don't see any water coming out of the circulating pump but I will check again along with the block drains.
You would agree the motor with the fluctuating water pressure is probably the problem?

you may have some blockage in the system did you back flush before putting the new sea pumps on, I think 30psi is a bit much for those motors

Get creative with cell phone vid or GoPro type camera. Mount near warm water sources. Ie: block drains, recirc pump/ exh hoses and drains

No I did not. The impellers in the old one were still in tact. I thought maybe one of the housings was cracked and rather then rebuilding them I chose to install 2 new ones.
Would it be possible the oil cooler has a crack in it that only opens up under higher pressure?