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OMC outdrive compatibility

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hometeem

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I have a 4.3 4v omc and my upper gears on my outdrive are siezed up. While taking it off and getting some numbers off it I realized that it has 3.0 stamped on it under the engine. Are the 3.0 amd 4.3 compatible or should i be replacing the whole outdrive with one from a 4.3 L? First time poster so thanx for any advice in advance.
 
thanx for the quick replies folks! i would rather just replace the upper case but cant figure out what to replace it with. Its a 1989 omc 4v 4.3L engine but my outdrive says the engine is a 3.0L. I cant find any website that correlates with the numbers im getting off the outdrive? Mod 986321 ser T0716790 ?
 
Also how in the hell did i end up with a 3.0ltr outdrive on my 4.3 engine? Could this be why seized I my upper gears. I have found a whole outdrive but did some other work have to be done to mount the 3.0 l outdrive to the 4.3 engine that i now have to undo?
 
seizing the upper gears is actually pretty common. So is ruining the forward/reverse gears. I seized my uppers too. The biggest cause is not filling the oil properly. 1) Open fill on top of upper case and Drain oil 2) Install drain plug 3) Remove middle plug 4) Connect oil pump and pump in oil until you see it on the upper fill stick (Just shy of 2 quarts) 5) Install upper fill 6) Remove pump/quickly install middle plug 7) run the boat to get rid of bubbles, check level at top fill on top of upper casing and refill from that point as needed. 8) Check level on top of casing often for at least the first few times you take the boat out.

From what I've heard they're all compatible with each other. Though I haven't seen any paperwork or done much research to confirm this fact. I swapped in an upper casing from a 5.7L into my 5.0 and haven't seen any difference. I'm sure you have a 3.0 outboard on your 4.3 inboard because someone swapped it at some point, most likely for seizing the upper gears like you did.
 
Maybe i don't get it. Won't be the first thing or the last i don't understand.

Someone buy's a boat or car, wants to work on it diy...but doesn't buy a manual, and doesn't keep the oil full in the drive engine or whatever.

I just got rid of a 1976 arrowglass bowrider with a 1976 70 hp evinrude.

It ran perfect with perfect compression...original gears and i never seized nothin on it.

Putting a 5.7 on a 5.0l engine or the other way around will work.

Putting a 3.0 drive on a v8 ain't gonna work.
 
Master mechanic said:
Maybe i don't get it. Won't be the first thing or the last i don't understand.

Someone buy's a boat or car, wants to work on it diy...but doesn't buy a manual, and doesn't keep the oil full in the drive engine or whatever.
Click to expand...

If you're referring to me when you say this... it wasn't exactly my fault. This boat actually belongs to my father-in-law, he brought it down to me to sell for him. Told me "Don't worry, I just had my mechanic change all the oils/fluids etc". I asked again, what do I need to check before I take it out? He said, just check the oil in the engine, the outboard is fine, it's never had a leak in it and he just filled it up. Took the boat out with a potential buyer, 2 minutes later cruising at 25 the boat dies and comes to a fast stop. Lesson learned. Don't listen to your father-in-laws!

I found out later that his mechanic "used" to repair boats, but now works for him in his RV repair shop.
 
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my last post was out of frustration but the first part was retorical of course. im a first time i/o boater so i had someone else get it ready for me this spring and from what i gather he is used to mercs with only 2 plugs so the top prob wasnt filled. from the research ive done it seems like the 3.0 and 4.3 are compatible. The complete outdrive i was lookin at has sold already so now im lookin at puttin a rehabbed top on my lower. My upper has 3.0 stamped on it but i think i can get a 4.3 upper which will match up. I have checked the prop spline and it has 15 gears which impies it wasnt switched to a 4 cyl outdrive which has 13. Anyone see any probs with this? Thanks for all the help folks!
 
you may have a newer 3.0 outdrive complete on there.
After 1990, 3.0 lowers had 15T splined propshafts like their V6 and V8 counterparts
The 13T smaller lowers were only used on 2.5 and 3.0 Cobras until 1989

Also, the tag on the drive doesn't always match the gears inside. A rebuilder may grab any upper housing and use it to build an upper. The upper cases are the same from a 2.3L to a 5.7L. They don't always take the old tag off.


A 4.3 should have 21:19 upper gears - I'm not sure about lower ratio - The Seloc manuals are good for comparing ratios model to model with their charts
 
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