Oil in raw water exhaust - trans oil cooler failed?

[jwa]

Actually, my bad. You're saying 2600 is only 200 from max attainable, and that is correct. I will be looking for the sweet spot for cruising as you mentioned.

[deblen]

Suggest you check the raw water hose (intake) from seacock to RW pump suction for collapse during high engine speeds.
As said,check for obstruction of RW seacock on outside of hull. Plastic & other debris could be partially blocking it (& could have floated away by now)
As a mechanic,I think you have done an excellent analysis of the symptoms & possible causes,but it could just be due to a temporary overheat from the cooling system.

Len

[jwa]

Thanks Len. I will take your advice on all points.

[exMaggieDrum]

Some very good posts here! RWA - you seem to be on the way to figuring it out.

My "new" 1981 boat I got a couple of years ago has pretty constant black smoke. I checked everything out that I could. I can't make even close to rated RPM's so I believe the prop is way too big with too much pitch. I plan to replace it next haulout. I think I will put on a folding prop anyway.

But if you are close to rated RPM then you may not have that problem, or, as noted, you just overworked the motor for a bit.

Good luck. This has been instructional for me.

[jwa]

Going to check on the engine this afternoon. If it starts up and has oil pressure and isn't overheating or crapping out black stuff, we'll change the oil and filter and call this a lesson on RPM management! Will also take all the other great advice you all provided and make sure the cooling circuits are clear and flowing properly.

Great having a forum like this to brainstorm!!

[jwa]

Great news! Went to the boat, and she started right up, full oil pressure, no smoke, oil/fuel in the exhaust, weird noises or anything else. Didn't get to take her out to test under load, but I'm going to change the oil/filter before doing that anyway. Dodged a bullet on this one! I'll keep it under 2400 RPM or so as a rule going forward. Will also check running gear and thru-hulls as well as per all the great suggestions from you all!

Thanks again!

[deblen]

Originally Posted by jwa

Great news! Went to the boat, and she started right up, full oil pressure, no smoke, oil/fuel in the exhaust, weird noises or anything else. Didn't get to take her out to test under load, but I'm going to change the oil/filter before doing that anyway. Dodged a bullet on this one! I'll keep it under 2400 RPM or so as a rule going forward. Will also check running gear and thru-hulls as well as per all the great suggestions from you all!

Thanks again!

That's great!
When you do go for trial,suggest you run for 45min. or so at 2400. If temp stays at 180,then try gradually increasing revs 50 at a time,run for a few minutes & keep repeating to see if temp starts increasing.

[deblen]

Could be a simple sticky t-stat.

Maybe check inside the RW pump for wear on the cover,etc.

Lots of good info here on a variety of boat things:
www.marinehowto.com

Consider a Speedseal kit if RW pump is worn. Welcome to Speedseal

[Stu Jackson]

Originally Posted by deblen

That's great!
When you do go for trial,suggest you run for 45min. or so at 2400. If temp stays at 180,then try gradually increasing revs 50 at a time,run for a few minutes & keep repeating to see if temp starts increasing.

Good advice. Everyone should do this regularly. When we first got our boat it had a 2 inch HX that, under full revs (M25, 3,000 max, 2600+ cruise) WOULD always overheat. Solution was a 3 inch HX. No issues ever since (i.e., 17 + years of the 18 we've owned the boat).

Always good to know what your limits can be.

Good luck.

[MarkSF]

Originally Posted by Stu Jackson

Good advice. Everyone should do this regularly. When we first got our boat it had a 2 inch HX that, under full revs (M25, 3,000 max, 2600+ cruise) WOULD always overheat. Solution was a 3 inch HX. No issues ever since (i.e., 17 + years of the 18 we've owned the boat).

Always good to know what your limits can be.

Good luck.

When I upgraded my HX from 2" to 3" it became obvious what was wrong with the performance of the old one. Essentially, I was mostly in open-loop mode as far as the cooling system went - thermostat wide open, and coolant temp varying from 175 to over 200, depending on throttle opening. I couldn't use full throttle as the temperature would creep up until I chickened out.

With the new 3" HX, the coolant temp sits at 175F, the thermostat temperature, all the time - from idle to full throttle. This is as it should be.