Penta outdrive

[Billyoahu]

Aloha...I have a quick and hopefully not a dumb question: I have a penta 280 outdrive and would like to know if I could
connect it to a 4 cyl. engine instead of the current 8 cyl. The connection between the drive and engine, is it the same for
a 4 cyl. or 8cyl. Thank you in Advance Mahalo!

 

[smassey22180]

Not sure I would put that much effort into a 280 as it probably has the wrong gears in it. Cheap 3.0 outdrive combo deals are easy to find. Probably will be a Mercruiser though.

 

[K-2]

Not a dumb question and welcome to the site. Yes you could do that, but it's a lot of work and many parts will be needed. Do you know what 4 cylinder you plan on using? Also there is motor mounts and transom plate exhaust to think about, plus a lot more.

 

[jerryjerry05]

I think???The u-joints will probably need to be changed around.
I believe the 280 has about 8-9 splines and the 4cyl drive shaft has 15?
Or something like that.
The ratio is way off for the 4 but with a prop change it should work.

 

[captmello]

The only 4 cyl engines that connected to a 280 were the old Volvo motors. the V8's were GM with the exception of ford for a couple years in the 70s. Personally I wouldn't consider the switch for all the reasons mentioned above plus more that are not worth mentioning.
So the answer is yes, but its not practical nor a good idea, IMO.

 

[jeffnick]

My Volvo Penta 260A (small block Chevy V8) has an Aquamatic 250 drive. I bought a spare drive for $80 but it is for a 4 cylinder. The only difference I am aware of is the ratio in lower section of the outdrive --
4 cylinder = 2.15:1
inline 6 cylinder = 1.89:1
V-8 = 1.61:1

And I have been told that the lower sections of these drives are interchangeable if the proper technique is used to shim the bearing.

So from my perspective, If there is an Aquamatic currently on the 4 cylinder and the OP just wants to put the 8 cyl in it's place, there is a very good chance that it can be done with minimum effort.

I do wonder about a propeller change to offset the wrong gear ratio though, especially since both Merc and Volvo have different ratios for different sized motors.

 

[jerryjerry05]

Got this from a friend who knows a bunch about Volvos,
not sure if it helps or not????

the AQ260 was never fit with a 250 drive.

The 250 transmission is considered to be the "small bearing" transmission.

Main drive gear male yoke splined shaft is considerably smaller than anything after the 250.

The lower unit gears are bevel cut....... not Hypoid!

The suspension fork has inserts in it for the Rev Latch anti-rotation pins.

Yes, the various ratio change occurs in the lower gear unit....... and in all but the E drive!
The E drive is unique.

The AQ260 ratio would be 1.61:1.

 

[jeffnick]

jj05
Thanks for the info. My boat is over 40 years old and originally came with a Super Bee Chrysler and might have even originally been a stringer? Who knows how/when the 260A was installed? I'm not sure how to really tell which drive mine actually is - the cover says 250 but I'm thinking my outdrive is a 250 because of what I've gleaned from various sources...

If the propeller spinner is not equipped with the center locking bolt, then it's a 270, or perhaps an older 250.
(the prop shafts were not internally threaded for the locking bolt until the 280/285/275 etc.)
If you have this locking bolt, then it's a later lower unit.

If the transmission oil fill port is located near the 2:00 O'clock position just above the shift mechanism, it may be a 275 or later.
(the earlier 250/270 did not have a fill port here.)

If this is a single screw helmet pin, then it's a 250/270.
If it has the double bolt helmet pin, then it's a 275 or later transmission, of which may not necessarily tell you which lower unit has been installed by someone.