Oil Change and Gear Oil Change issue . Can you help ?

[dorrals]

I have a 1990 doral monticello 270. It has two 4.3L OMC Cobras

This is the first year I decide to do the winterizing on my own and I don't have much experience in this area so I'm learning. Please be patient with me as I'll probably ask a few questions to clarify.

Issue 1 : Oil change
This manual that I found (i don't have a manual like this in the boat) https://sunbirdcorsair.wordpress.com/2010/12/05/original-omc-manual-in-pdf-format/

stated the engine oil to be used is an SAE30, I almost bought it today but I'm glad I didn't as I just read on another site that there's a type of SAE30 that's used for things like lawnmowers and other land machinery and another type that's used for marine vehicles. Is this true ? If so, is there a good place to shop for this as I'm seeing that a gallon of sierra oil is ~$90CAD which I wasn't expecting at all.

Also, I'm curious as to whether there's any newer/better oils that would be better for my boat that weren't available back in 1990 when the recommendation was first made. I read some posts on here suggesting that but I got confused pretty quickly. So are there any recommendations/info on engine oil that you can provide ?

Issue 2: Gear Oil
Honestly, I don't know when this was last changed. I decided to drain it and it came out really milky (white and green), one side was much thicker but both were pretty thick and smelled awful. What could the problem be here ?

(I've already refilled one, but haven't done the other one as I noticed it was leaking from the propeller area, I took that off and it looks like it's mostly coming out of a screw - any ideas on this issue as well ? )

Any help would be greatly appreciated. Thanks !!

 

[alldodge]

Nothing wrong with 30W oil, many cars and trucks use 30W. Use what the manufacture of the motor recommends. Some use 15W40 Diesel, others 20W40 Merc stuff

White in the gear lube means there is a seal leaking. With lube drained pressure test the drive at 10psi rotating the shaft to see if it leaks

 

[Lou C]

Yep you can use straight 30, straight 40, Merc 25/40, or various brands of 15w/40 for the engines
For the Cobra drives I've used the Mercruiser High Performance Gear Lube for years, but your problem there is you need to find someone who can pressure and vacuum test the drives and find where the leak is.

 

[Scott Danforth]

Any of the oils listed above are fine. SAE 30 is SAE 30. Good for motor oil, power steering fluid, hydraulic fluid, etc

Pull your drives and pressure test

Check your alignment, bellows, u-joints and gimbal

 

[bruceb58]

Issue 2: Gear Oil
Honestly, I don't know when this was last changed. I decided to drain it and it came out really milky (white and green), one side was much thicker but both were pretty thick and smelled awful. What could the problem be here ?

(I've already refilled one, but haven't done the other one as I noticed it was leaking from the propeller area, I took that off and it looks like it's mostly coming out of a screw - any ideas on this issue as well ? )

Any help would be greatly appreciated. Thanks !!

Hopefully you refilled properly. You don't fill from the bottom...you fill from the middle screw.

 

[Lou C]

Yep you’ve got to do it the OMC way. Doing it that way 20 seasons worth never had a problem. Crowley Marine used to post OMC tech instructions on their site….

 

[Lou C]

OMC Cobra Outdrive Lubricant Filling | Crowley Marine

OMC Cobra Outdrive Lubricant Filling5001595

www.crowleymarine.com

 

[dorrals]

Yep you can use straight 30, straight 40, Merc 25/40, or various brands of 15w/40 for the engines
For the Cobra drives I've used the Mercruiser High Performance Gear Lube for years, but your problem there is you need to find someone who can pressure and vacuum test the drives and find where the leak is.

What do you mean by straight ? I'm not familiar with the terms.
I've had trouble finding SAE 30 marine oil. So far I've only found one product by sierra international available through amazon and it'd take a couple weeks to deliver - so I'm trying to understand other options.

25w40 and 15w40 sound pretty different. I've also seen 15w30 suggested.
Any rationale for these suggestions? Why would someone use X instead of Y ?

Unfortunately because I didn't get any notifications of replies I ended up just tightening up the screws and filling up the vertical drives with fresh gear oil based of the manual recommendations. One of them apparently i filled the wrong way (bottom plug) before I found out it was the wrong way and I filled the other drive the proper way. Any chance I can pressure and vacuum test them with the new oil in it ? Perhaps I can do it on my own with some youtube guidance ?

 

[dorrals]

Hopefully you refilled properly. You don't fill from the bottom...you fill from the middle screw.

Unfortunately I refilled one of them from the bottom before I learned that this specific model requires filling from the middle. Any idea on if this is a big deal ? What issue can come up?

Also when I filled the 2nd motor properly, i didn't get that vacuum effect the manual mentioned. Oil spilled out. I just put the screw back in anyways. Any idea why that might've happened?

 

[Lou C]

Straight means a single weight oil. You can use any of these choices but the one that is specifically blended for marine engines is the Mercruiser or Quicksilver 25/40.
When you filled the drives did you get at least 2 qts of gear oil in? Recheck the level with the dipstick in the top cover. If you follow the procedure I posted you will not have a problem but if the oil you drained had water in it the pressure & vacuum test must be done with the drives empty. I last had mine resealed in 2006 and it’s still fine I changed the gear oil yesterday & no sign of water. A well maintained Cobra will last a very long time.

 

[bruceb58]

What issue can come up?

You could wipe out your drive because of a large air pocket!

 

[Lou C]

Exactly you must do it as described in the link I posted above. Nothing complicated about this I’ve been doing it that way 20 years never had a problem.

 

[Scott Danforth]

I've had trouble finding SAE 30 marine oil.

No such animal as marine oil

SAE 30 is SAE 30. Go to Walmart, tractor supply, Napa, carquest, etc.

 

[Renken2000Classic]

No such animal as marine oil

SAE 30 is SAE 30. Go to Walmart, tractor supply, Napa, carquest, etc.

One thing to watch for - Wal Mart sells 2 versions of 30 weight oil right next to each other (and a little apart from all the rest of it). One is the vehicle stuff, and the other says "lubricating oil" or something like that. Very similar bottles.

 

[dorrals]

No such animal as marine oil

SAE 30 is SAE 30. Go to Walmart, tractor supply, Napa, carquest, etc.

No such thing as marine oil in general or no such thing as SAE 30 marine oil ?

Because the first I know is definitely false, but the second I don't have an opinion on as I don't know enough about engine oils.

 

[dorrals]

You could wipe out your drive because of a large air pocket!

Hmm, so is the only solution here is to drain it again and refill it through the middle hole ? Could I identify and eliminate large air pockets without the whole drain and refill procedure?

 

[bruceb58]

Hmm, so is the only solution here is to drain it again and refill it through the middle hole ? Could I identify and eliminate large air pockets without the whole drain and refill procedure?

That would be correct....or you could roll the dice.

Just drain into a clean container and put it back in...plus whatever additional you may have to put in.

Read this thread especially post #13

Proper OMC Cobra drive lube fill????

I have asked several OMC guru's a few mechanics and the one i personally found that has been doing this 35 years said the proper way to fill a Cobra is different from what others are telling me. I was told to fill thru the very bottom, once the fluid was running out the mid point hole place...

forums.iboats.com

 

[Horigan]

Just to keep things confusing, realize that the Cobra SX drive (Volvo joint venture) gets filled from the bottom.

 

[Lou C]

correct, those instructions I posted are for the 1986-1993 original Cobra.
The 94 and up Cobras are the same as a Volvo SX
as I said, I have done it this way 20 times over 20 years and never had a problem!

 

[bruceb58]

Just to keep things confusing, realize that the Cobra SX drive (Volvo joint venture) gets filled from the bottom.

Since the OP stated he had 1990 drives, I didn't even bother to ask if he had SX drives.