OMC Cobra 4.3L - Outdrive Oil Questions

[coolguy982]

I recently purchased a 1988 Thundercraft Citation 170 with an OMC Cobra outdrive on a 4.3L engine. This is my first boat, so I'm learning as I go. I've had the boat out on the water a few times and it seems to run great.

Tonight, I decided to check the outdrive oil using the dipstick on top of the drive. I put the trim down and unscrewed the dipstick to check the level. I noticed that there was a drip or two of oil hanging off of the dipstick but it was somewhat yellowish and not brown like standard motor oil. After reading many forum posts on this site, I wonder if this means I have water in the outdrive. I looked down through the dipstick hole and couldn't see any oil at all--just some metal parts. However, as I mentioned, the dipstick had some oil on it so I know it's not entirely empty. The boat was last on the water two days ago. When I first took it out on the water about a month ago, I noticed a brief oil sheen in the water while backing the trailer down the ramp into the water. It seemed to go away and did not persist, but I also wonder if it could be related.

Here are some questions I have:

1. Can/should I remove the entire top plate of the outdrive so I can see further into the drive and see how low the oil level actually is? If this won't hurt anything, I will do this and post some pics of the oil color.

2. Can/should I just pour some more gear oil through the dipstick hole to top it off and be done with it?

3. After reading other posts, it seems I might want to drain and change the oil, replace the drain screw gaskets, and remove the impeller to see if oil is leaking under it and then see if water gets in the drive again after all of that? Does that sound like a good plan of attack? I'd like to do everything I can before having to entirely remove and disassemble the outdrive.

4. If I hook the boat up to muffs and run water through the drive and then turn the motor on, where exactly on the outdrive should I see water coming out? (i.e. if I do have a leak would this be one way to help tell where it is?)

 

[cr2k]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

If you have oil on the dipstick you are close. There is a ring on the lower end of the stick and that is the proper level. You may drip a little in the top, but it will take forever and may give you a false reading.

When you drain you pull the bottom plug and the top plug/dipstick. When you refill you replace the bottom plug and go up to the plug that is a little higher and forward and fill from there until it is right on the stick. If you fail to fill this way you may soon be replacing the drive.

Use any regular 90w or 70-120w regular or synthetic blend gear oil. You will need to get a pump so you can pump it in from the bottom NAPA or any marine store will have this.

When running on muffs (drive as far down as you can get it) you see water from the relief ports which are just below where the drive attaches to the boat, from the bottom of the exhaust bellows (holes in here are factory) and maybe from the prop hub.

I would pull the prop and see if there is any fishing line on on the shaft. If so don't grab an end and start pulling, try to work it out as a coil so as not to damage the prop seal. Remember to grease up the prop shaft splines.

The water pump is behind the cover on the back of the drive.

 

[DBreskin]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

I noticed that there was a drip or two of oil hanging off of the dipstick but it was somewhat yellowish and not brown like standard motor oil. After reading many forum posts on this site, I wonder if this means I have water in the outdrive. I looked down through the dipstick hole and couldn't see any oil at all--just some metal parts. However, as I mentioned, the dipstick had some oil on it so I know it's not entirely empty. The boat was last on the water two days ago. When I first took it out on the water about a month ago, I noticed a brief oil sheen in the water while backing the trailer down the ramp into the water. It seemed to go away and did not persist, but I also wonder if it could be related.

Here are some questions I have:

1. Can/should I remove the entire top plate of the outdrive so I can see further into the drive and see how low the oil level actually is? If this won't hurt anything, I will do this and post some pics of the oil color.

2. Can/should I just pour some more gear oil through the dipstick hole to top it off and be done with it?

3. After reading other posts, it seems I might want to drain and change the oil, replace the drain screw gaskets, and remove the impeller to see if oil is leaking under it and then see if water gets in the drive again after all of that? Does that sound like a good plan of attack? I'd like to do everything I can before having to entirely remove and disassemble the outdrive.

4. If I hook the boat up to muffs and run water through the drive and then turn the motor on, where exactly on the outdrive should I see water coming out? (i.e. if I do have a leak would this be one way to help tell where it is?)

The yellowish color of the oil is correct. If you have a water leak the motion of the gears will mix the oil and water and it will look like a milkshake. It the lube is clear, you do not have water leaking in.

You can remove the top plate, but it's probably not necessary. You should remove the dipstick; dry it off; reinsert it fully (screwing it in all the way); and remove it again. The oil level should show to the groove on the dipstick.

If the oil level is low, you can top it off through the dipstick hole.

It doesn't seem like you need to drain and fill the lube. If you do, be sure to use high-viscosity gear oil. You mention removing the impeller but I guess you mean propeller, and you suspect there may be a leak at the prop seal. The impeller is part of the water pump system.

Running on muffs isn't going to help locating water leaking into the drive. Water can leak in through many different places: the gasket where the top and bottom halves of the case meet; the top cover gasket; the prop seal; etc.

 

[jerryjerry05]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

You can dribble some oil in the top.But to remove all the old and refill:you MUST!!!!! fill it from the side as there is an air passage that will not get filled and you will burn up the drive costing LOTS!!!!
Drain it and see what comes out.There is a fill plug on the side remove that too.J

 

[coolguy982]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

Thank you for all of the quick replies. Some follow-up information and additional questions:

When I first pulled the dipstick, I did see a drop or two of oil on it, but after cleaning it, reinserting, and taking it out again, there was no oil on the dipstick at all. I looked through the screw hole and couldn't see any oil in there--that's why I thought to take off the whole top plate so I could better see just how low the oil level is. The fact that there was a drop of oil on the bottom of the dipstick tells me that there is oil there, and maybe it rose high enough or got thrown up enough when it last ran to hit the dipstick. When looking down through the dipstick hole, I should be able to see the oil level, correct?

I would say the oil color sort of looks like eggnog. Not white and frothy like a milkshake, but definitely not brown and clear like standard motor oil. Is it supposed to look like this or do you think I have water in it?

I did mean the impeller. I read in another post that there could potentially be an oil leak coming out of the impeller/water pump area and that I should check that area to see if oil is present.

I have an OMC manual and am aware to drain from the lower plug and fill from the middle using an oil pump.

Where can I find new drain plug washer/gaskets for the drain plug screws?

 

[bruceb58]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

When you check the oil, you don't screw in the dipstick to check the level. You pull it out, wipe it down and then just insert and pull back without screwing it back in to check.

 

[coolguy982]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

When you check the oil, you don't screw in the dipstick to check the level. You pull it out, wipe it down and then just insert and pull back without screwing it back in to check.

Even when I did that, there was no oil on the dipstick after inserting it and pulling it back out without screwing it in. That is why I looked in through the hole to see if I could see the oil level, but I just saw an empty cavity. I cannot explain why there was oil on the dipstick when I initially unscrewed it.

 

[bruceb58]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

If you were running it before you looked, it could have easily gotten flung onto it while the gears were spinning.

Definitely drain it and if you are really curious, measure the amount you drain out.

 

[coolguy982]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

If you were running it before you looked, it could have easily gotten flung onto it while the gears were spinning.

It hadn't been run for two days. But since the oil doesn't register on the dipstick now and since I only see an empty cavity when looking through the dipstick hole, that means I either need to add oil or drain/replace, correct?

 

[bruceb58]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

If it were my boat and I just bought it, i would be doing a lot of things including draining the drive oil. I would definitely also be pulling the drive and inspecting inside the bellows, lubing u-joints, inspecting the gimbal bearing and checking the alignment.

 

[HT32BSX115]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

When you check the oil, you don't screw in the dipstick to check the level. You pull it out, wipe it down and then just insert and pull back without screwing it back in to check.

According to the OMC service manual, that's how you initially check it on a drain-refill. ("To allow for a slight over-fill")

On subsequent oil checks, it's done with the dip-stick all the way in.....

 

[bruceb58]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

Unfortunately, I sold my OMC manual with my boat. I thought that was a disparity between the Seloc and the real OMC said that you don't screw it in.

 

[bruceb58]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

Is it possible we are both correct?

 

[coolguy982]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

I looked at things a bit more tonight after reading through all of your comments. I also took a few pics and attached them here.

Problem #1: I ran the boat on muffs and noticed water coming out from under the impeller cover. I thought it may be coming out of the drain hose, but after removing the cover, I saw that it is coming out from where the impeller housing meets the outdrive in one spot. The first pic shows exactly where it was coming out at the red arrow--just in that one area. In the pic you can see it spraying a bit and also flowing out over the bottom lip of the impeller area. I took the impeller off and took some more pics. It looks to me like the impeller is in good shape. Do you agree? The metal plate/gasket is also shown. In the pic of its (black) backside, you can see that there is a small piece of the black felt missing in the same area that the water was leaking. What should I replace here? Just the metal plate/gasket? The o-ring in the impeller housing? The entire impeller housing?

Problem #2: I also took off the gear case cover just to see how low the oil level is. You can see that in the last picture. Is it safe to assume that I have water in the oil? The oil level also seems way too low. I already have the oil, nylon washers, and oil pump. Should I drain/refill the gear lube oil and see if water enters the oil again? Anything else I should try (that hopefully wouldn't require that I remove the entire outdrive)?

Problem #3: Also in the last photo, I put a red arrow that shows some nicks in the metal shaft. There aren't very many, but there are some. Is this a big problem or not, and what could have caused it? The low oil level?

Your thoughts/help are appreciated.

 

[johnbo]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

Judging by the picture of the inside of the gear case, you definitely have water in the oil. It looks like there might be more water than oil. Sorry, it sounds like you've got some more work ahead of you.

Later,

johnbo

 

[MRS]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

Drain the outdrive and fill it will take 64oz. when empty. Check with dip stick not screwed in after filling, after running on muffs or on the water then screw all the way down to check that is from the omc manual. When ever I get a new old boat to me that is the first thing I do plus the impeller cover does have a pee hole on it and water does come out of it.

 

[bruceb58]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

Don't even bother putting oil in it until you drain what you have in there and have the drive pressure tested to see where all your leaks are. You definitley want to pull the drive as well to see if there is water in the bellows.

 

[HT32BSX115]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

Don't even bother putting oil in it until you drain what you have in there and have the drive pressure tested to see where all your leaks are. You definitley want to pull the drive as well to see if there is water in the bellows.

Yeah..... I absolutely agree with the above!!

Is it possible we are both correct?

Well, of course!


Although it didn't say to do it like that in my previous (1987) manual. It only said to "rest" the dipstick on the threads and fill it to the "full" mark during initial fill "to allow for a slight overfill"..... presumably to allow for the trapped bubbles that invariably occur even when when you fill it "right"!!

 

[bruceb58]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

Even with my current drive, A Volvo, I always check it after a couple hours. I also always check it the day before I go out before I do my test start of my engine.

 

[Lou C]

Re: OMC Cobra 4.3L - Outdrive Oil Questions

I agree that drive needs to be removed and pressure/vaccum tested before you do anything else...and the impeller when installed needs OMC gasket sealer on the gasket between between the wear plate and the housing and also on the o ring that goes round the impeller housing itself...I have never run mine with the cover off but I don't think that water should be coming out at that spot. there is a pee hole but that is connected to the rubber line that goes down to the upper gear housing...