1971 Mercury 650 parts interchange & short shaft questions

I have a 1971 long shaft 650 Merc. I've been looking for a short shaft version but have only found long shafts anywhere close to what I can afford, or anywhere nearby. In my search, I've found another long shaft '74-76 650 w/ a blown powerhead. Are there any parts that are interchangeable w/ my '71? I'd be interested in the blown motor if I can use the lower unit on my 650. It'd be worth the asking price to have a spare lower.

I know of 2 4cyl short 650's 1 runs (maybe, haven't seen it run), 1 ???, but both are 6+hrs away. W/ cost to go get 'em, and go through 'em, I'm hesitant to take the plunge on either. Plus w/ the 1 boat in dry dock, thread in my signature, the possibilty of a 2nd boat pending, 1972 Century Raven O/B w/ running motor.

In my resto thread there has been some discussion about raising my transom, but I'd rather not.

Are there other years, models that fit my 650? I tried to find a thread that mentioned changing to stronger lower unit that had taller gears(?2.3 up from 1.6?). Apparently it had stronger drive gears then a mid 60's 650. But I can't seem to locate where that was mentioned. Can anyone confirm that, w/ years & models?

My FireFlite is rated up to a 75hp, so I could also be persuaded to move up to a larger then 650 motor if it would also be easier to find the short shaft version.

I will probably leave the transom where it is, and use this 650 as a long shaft, unless I can put together a different setup w/ alternate years & model parts.

Thanks

Re: 1971 Mercury 650 parts interchange & short shaft questions

The 650 Merc from '72 to maybe '76 were three cylinder engines.None of what you are looking for will interchange.
The midsections from 1963(I think) to about 1986 are supposed to use the same lower units with small variations (gear style,gear ratios) so you have a pretty large inventory of engines to be looking at.
My 650 has (by part number) an L6 1500 or 150 HP lower unit on it with the correct 150hp gear ratio (2.1) in it.
You did not say what the length of your midsection has to be.The long leg which is most common is for a 20" transom.I also have a 1970 650 with an XL leg on it which is 25".
My other 4 cylinder 650 is a 15" midsection with a 5" extension in it.
There are many options available for you to look at,it does not have to be from a 650.Ron G

Re: 1971 Mercury 650 parts interchange & short shaft questions

PERFECT Thanks Ron!

I have a good 4cyl power head from '71. I'm looking for a short shaft middle section that will work with the powerhead I have, the lower unit is good too.the 15" short shaft middle section. Hopefully, this will make it much easier to find a setup that works on the FireFlite.

Most helpful thank you again

Re: 1971 Mercury 650 parts interchange & short shaft questions

Hey bud, I have recently spent a TON of time with interchangeability of these L/U's. If you have any other ?'s regarding them just shoot me a P.M. If I can't answer your ? I certainly know who can!!

Re: 1971 Mercury 650 parts interchange & short shaft questions

The only midsections that will work are from a 1969 to 1971 4 cylinder 65hp and 80hp as they are both 8 bolt power heads. All inline 6 engines are 2:1 ratio except some early 115 & 135 engines which where 1:78 ratio and all 4 cylinder (crossflow) are 2:3:1 ratio. Finding a midsection shouldn't be to hard ,finding a GOOD short shaft drive-shaft will be the biggest problem.