Excessive oil pressure / oil cap

[tonyvail]

I have an 86 OMC 4.3L. The original owner was a race car mechanic. He rebuilt it, bored it out, put in bigger pistons and new parts. I've had it for many years now. It has always gone through oil and the oil pressure gauge has always pegged the oil pressure guage. No running problems, just a lot of oil pouring through the seals dumping in the transom. what a mess it makes. I always assumed that the mechanic put in a high pressure oil pump causing the issue.

Recently I had a car problem with oil forcing through the seals. This happened right after replacing the oil cap after my son lost it. I went down to Kragen and they sent me off with this oil cap. Now I realize that the Kragen oil cap isn't vented and caused excessive pressure. I'm wondering what oil cap was supposed to be on my 4.3L cobra? Does anyone know if it is supposed to be vented? It isn't. Also, even if the OEM is not vented, maybe a vented cap would be good for my particular engine situation?

 

[Bondo]

Re: Excessive oil pressure / oil cap

I've Never seen High Oil Pressure cause any seals to Leak.......Just How High are we talking,..??...

And,........ If you've owned this for Years,........ Why haven't you Fixed it Before This,..??.....

On a motor that old,... There should be 2 Open Vents from the top of the Valve Covers to the Flame Arrester........

Additional Venting Isn't going to Fix Bad Seals...........

 

[tonyvail]

Re: Excessive oil pressure / oil cap

The motor had been recently rebuilt by the previous owner with fresh parts when I took it in for a mechanic to check the oil seal leaks many years ago. The boat still has very low hours on the rebuilt motor after all of these years. I don't use it much. It does start up and run very well. The guage goes to 80 or so and will peg at 4000 rpm or so. The marine mechanic wanted $1000 to pull the motor and replace the oil pump and seals. They figured the oil pump was to powerful but would not hurt anything if I kept oil in the motor. Since the motor runs very well and has low hours on it still, I never saw a reason to spend that much money. I just keep putting oil in it. The consumption isn't bad if you keep the rpms modest. The mechanic seemed pretty sure that the seals leaked because of a non stock high pressure oil pump. Of course you have to pull the motor to confirm what oil pump is in it.

After the experience with a car this week, I'm thinking that other things can create an environment forcing oil out of seals. During my reserach of the leaking car I also learned that there was a oil relief valve in the motor that lets oil loose if the pressure gets to high. The pressure was getting to high in the car because the valve cover wasn't vented after replacing the oil cap with the wrong type. This made oil gush out of the car. Problem in the car is gone with the unvented filter off. I'm wondering if my boat motor doesn't have such a relief valve, or if additional venting such as adding a vented oil cap would reduce the pressure on the seals.

 

[speedholes]

Re: Excessive oil pressure / oil cap

I hate to say it, but it sounds like RTV was used on the oil pan gasket and broke off into the oil pan. From there it gets sucked onto the oil pickup screen, causeing the high pressure reading. Many people have rebuilt motors and put the high volume oil pumps in them, then see the pressure increase and assume it is the HV pump. THis is not the case, the pickup is clogged most of the time. Even with racing oil pumps, PSI should be readable on a standard guage. The only way to check this is to remove the oil pan and clean the pickup screen.

If it uses oil now, it might have been due to lack of oil caused by the clogged pickup, leading to premature wear, thus oil usage.

 

[tonyvail]

Re: Excessive oil pressure / oil cap

I don't think it burns oil. It dumps about two or three quarts in the transom every time out.

 

[Don S]

Re: Excessive oil pressure / oil cap

Have you tried the age old trick of looking while you are running to see where the oil is coming from?
Also, the oil is probably accumulating in the "Bilge" of your boat, not the "Transom". The Transom is the vertical bulkhead between the water and the inside of the boat. Usually has the transom shield with the outdrive attached to it on the outside of the boat.

 

[Reel Poor]

Re: Excessive oil pressure / oil cap

it gets sucked onto the oil pickup screen, causeing the high pressure reading. Many people have rebuilt motors and put the high volume oil pumps in them, then see the pressure increase and assume it is the HV pump. THis is not the case, the pickup is clogged most of the time.

If it uses oil now, it might have been due to lack of oil caused by the clogged pickup, leading to premature wear,

How can a "lack of oil caused by the clogged pickup" be "causeing the high pressure reading" ?

Lack of oil causes a low/no oil pressure reading.

 

[Bondo]

Re: Excessive oil pressure / oil cap

I don't think it burns oil. It dumps about two or three quarts in the transom every time out.

I Can't Believe anybody would Live With such a Massive Oil Leak,..........
Especially without Even Looking to See, Where it's Leaking........

I can Just Imagine the amount of Oil you've Dumped into Your boating Waters............

 

[cobra 3.0]

Re: Excessive oil pressure / oil cap

Yeah that oil leak is SICK! :/

 

[bamadave]

Re: Excessive oil pressure / oil cap

You're pumping that crap out into the water when the bilge pump comes on. Be just a little bit responsible and repair it. There is not 1 boater here that say that what you are doing is exceptable. And no, a oil cap is not going to fix it.