Engine purchase potentially today need info on this engine (pics)

[Bondo]

Now my mechanic is recommending I change out the housing and drive to a newer style for this engine. He said 84 or newer. Is this a good idea? Once the engine is out it wouldnt be anything to pull that and upgrade. Would that then be a gen 2? He kept calling it a "R" drive saying I'd be stuck in the 70s if I leave it and slap a drive on existing. So much to take in I tell ya

Ayuh,..... That gets ya into the Alpha 1 vintage of drives, 'n motor accessories,......
Rear motor mount spacin' is the biggie there, MC-1 is wide, A-1s narrower, up to current production of 'bout 9",....

 

[Tmacular]

That is a later MC1 gimbal and bell housing. You can use any drive from 1966 to 1990... For the 350 engine, use a ratio of 1.5:1 (or 1.47:1 for later drives)... Unless you are installing in a particularly heavy/big boat, in which case you can use higher reductions.

Chris.......

So I got a guy who has an outdrive for me local. He said he came off a 305 around late 80s and was 1.5 . But then an hour later called me back saying it's a 1.65 ratio? Is it even worth it to purchase this one (400) and do a prop adjustment or should i just stick to the 1.5/1.47 only

 

[achris]

1.65 is what I'd be puttng in. :thumb:

 

[Tmacular]

1.65 is what I'd be puttng in. :thumb:

Thanks again Chris. Is there any modification needed for such a small diff. Just slap it on with a normal prop and go? Pressure test revealed top seals need replaced but that's no biggy.

 

[achris]

Do a 'prop test' as standard. Put on a prop, take for a run at WOT and check the revs (with a calibrated tacho, not a dash tacho!). If the revs are outside the engine spec WOT, then change the prop accordingly. (Increase prop pitch will decrease WOT revs)....

And if you think about it, 1.65 is only 10% higher than 1.5, so if you would have been running a 19" prop on the 1.5, you'd need a 21" on the 1.65... And the higher pitch props are slightly better in efficiency....

Chris..........

 

[Tmacular]

Do a 'prop test' as standard. Put on a prop, take for a run at WOT and check the revs (with a calibrated tacho, not a dash tacho!). If the revs are outside the engine spec WOT, then change the prop accordingly. (Increase prop pitch will decrease WOT revs)....

And if you think about it, 1.65 is only 10% higher than 1.5, so if you would have been running a 19" prop on the 1.5, you'd need a 21" on the 1.65... And the higher pitch props are slightly better in efficiency....

Chris..........

Thanks Chris! Appreciate the time to teach a young gun! That's the information I wanted to know for future as I wasnt sure how the prop to gear ratio formula worked.

 

[achris]

.... how the prop to gear ratio formula worked.

new ratio/old ratio * current prop pitch = new prop pitch.

That will get you pretty close. It's not exact because of the different efficiencies of the different pitch props and it also depends on exactly where the old ratio WOT revs were (because, 'power band' )

Chris.........