MACDAD260

Well, I have been on the water twice now with the new Gen V carb 502 since replacing the 7.4L So far I have easily picked up 5 mph on a few short bursts. I am using all the stock components from the 7.4L plus I went from a 21" Mirage + to a Bravo 1 24" prop. The only problem is that the oil is getting hot and I am not even running hard. I installed a Gaffrig Oil Temp Gauge with the sending unit tapped into the remote oil filter bracket. It measures the oil temp directly coming out of the engine before it goes through the filter and the cooler. Any sustained run over 3000 rpms and the oil goes to 230* or higher. It takes a few minutes to get there but I think that is way too high of a temp for part throttle cruising. What I don't understand is why is the oil getting this hot when I am not even working the motor. With the 7.4L I would run nearly wide open for long periods of time and when I slowed down to an idle the oil pressure would be fine. Now the oil pressure drops to 20 at an idle if the oil temp has reached 230*. I even replaced the stock 11 psi oil filter bypass in the block with a 30 psi unit in case the oil was somehow not going through the filter and cooler. I guess I need a larger oil cooler. Anyone have any suggestions as to which one would work best. I have looked on the Eddie Marine website at their coolers. Who else makes them? What do you guys do for oil coolers that build mega HP engines? Any advise will be appreciated.

BTW, the water I am running in is only in the low 40 s. If the cooler is too small now what will happen when the water gets in the 70 s?

Thanks, Doug

Interceptor232

What I think the problem is the fact that you engine is working much, much harder than it should. Your engine load is very very high and thus the more fuel must be added to keep the same rpm, and more heat is generated. You are getting more speed but you going to pay a price for it by wearing your engine out much sooner. I have a floscan meter hooked up to my boat, when I have about 10 gallons of fuel no gear and just my self on the boat at 2500rpm I will burn about 8gph, load the boat up with 1500lbs more people fuel and gear I will burn 14gph at the same rpm plus my exhust temp and oil temp go way up due to the increased engine load, far better to be under pitched prop than over... My advice is dump the 24" before the engine dumps you...

MACDAD260

Interceptor232, Thanks for your reply. I don't think the motor is overloaded. I tried a Bravo 1 24" prop on the boat when it had the original 7.4L engine and it worked great. The stock motor could turn that prop at 4300 rpm which is in the factory operating range of 4200-4600 for that motor. With the 502 it takes very little throttle to run at 3000 rpm. Besides, everyone I know runs a Bravo 1 24" prop or bigger with a 502. When I started this project I realized that the 454 Mag and the 502 Mags run bigger oil coolers from the factory than a 7.4L. I was hoping to get away with using the small cooler to save money but, I quess there is a good reason for the larger coolers on the higher hp engines. I am hoping that someone who has done this swap before could share their experience and tell me what they did to solve the hot oil problem.

Thanks, Doug

I am also running regular 10w-30 oil for the first 5-6 hours of break-in. Perhaps that is why the oil pressure drops at idle when the oil is hot. 15w-50 Mobil 1 will be going in at the first oil change. In the old motor I ran the Merc 25w-40 and never had a problem. That motor has 508 hours on it and runs like a champ.

Mr Gadgets

Hey Doug,
Glad to hear you are running!! The oiling problem you are having might not be as bad as you think. You said that oil temp was 230 measured at your remote oil pad.. before the cooler. I dont think that is out of line. And your right, the 10-30 is a bit thin. I always break mine in with 20-50 Valaline racing oil. My truck motor wasnt happy with 10-30 either. Swithed to 20-50 and it stays right up there.
There were some threads a long time back that talked about oil temp and pickup points. I would be willing to say 280 before the cooler isnt too bad. but that would be some hard running. You need to see what it is after the cooler. I plumbed mine so that the last thing the oil sees is the filter before it hits the motor, that way you see cooled oil.
Check out CP performance as well as Eddies and maybe Teagues. You might look for a "take off" 502 cooler. Some guys upgrade when they modify heavily and take the old cooler off.. That should be all you need!! What about the oil lines, are they 5/8" id.. that is min I believe to flow enough oil thru all the hardware..
Good luck and keep us posted. That 24" Bravo should be just the ticket for you!!

Dick

US1 Fountain

I'm using the oil t-stat/filter unit on my blown 502. It was running 230 right from the oil pan last weekend. I believe that is the idea temp.

Waterfoul

Doug, 230* is not too hot. That's hot enough to boil out any condensation but not hot enough to hurt the oil. When you switch to a thicker, synthetic oil, you will see some drop in temp and rise in pressure. I did with my last motor. I would still probably look for a take off 502 cooler though. Just for peace of mind if nothing else.

STill don't have my motor installed. Having trouble finding somebody to drop it in. Can you help???

Cord

I don't think you have an issue with oil pressure either. The rule of thumb is 10psi per thousand rpms. So having 20psi at idle is more than enough.

MACDAD260

Thanks for the replys, guys. I feel a little better now with the fact that you all think the oil temp is not out of line. I might just change the oil to a 20w-50 before I go out again and see what happens. If the temp stabilizes and the oil pressure stays up at idle then I will know that the 10w-30 is the problem. I am still going to upgrade the cooler though, just for peace of mind if nothing else.

Mike, I would be glad to help you with installing your motor if your boat will fit inside my barn. The door is only 8 feet high. Call me on Monday and we can talk about it. 318-1569.

See ya, Doug

obnoxus

Like was said, that is an ok temp before the cooler, and will drop with syntetic oil,,,,Also, I am sure you checked but make sure you are not overfilled on oil, this will raise temp also as more oil hits the bottom of the pistons.

US1 Fountain

Should have also noted that I just run straight Valvoline 40w.