Marinette Boat Forum

I've been doing some research and poking around for available engines and transmissions to repower my Sportsman with. The engine in the boat is going for scrap so I can choose whatever I'd like for a power plant. Currently, I'm leaning towards a 350, in large part for parts availability.

My next question is: what transmission to use? The velvet-drives seem pretty reliable and parts availability acceptable, and affordable. Would a 71c be able to handle a 350 without being on the upper limit of its specs? What about a 72c? Any other transmissions worth considering? I'm a firm believer in having a cushion from upper limit ratings for reliability and longevity.

Would I need to bump up to a 1-1/4 inch shaft?

Thanks for the knowledge and wisdom,

Joe

Velvet drives are one of the most reliable, robust and simple transmissions ever built. JI Case used a modified version with an automotive style torque convertor in their backhoe loaders for years. Paragon is good, but parts are getting harder to get, and I personally think they are not as robust. ZF makes a good unit. Velvet drive is probably the best bang for your buck. The general rule of thumb is a 71 series is good for any small block while a 72 series is for big blocks. Obviously if a high hp small block was built you would want to move up to the 72. For reference, you can reverse the rotation of a velvet drive just by re-clocking the pump. No disassembly required.

If you are interested, I have a complete chevy 305 from a chris craft, with 1:1 paragon that I can part with. A 305 is probably not your first choice, but this would give you everything needed to marinize any 86 and older small block chevy (with the exception of a 383 stroker or 400). If you did not want to use the paragon trans, a velvet drive will bolt in its place. PM me if interested.

The 72C or 10-18 is about 3/4" of an inch longer. The interchange other than the length. You'd have to check your prop shaft length as I've seen issues on some boats when switching to a 72C that the rudder hits the prop on sharp turns. To clarify on reversing rotation re-clocking the pump is only for pumping fluid. Forward gear is always crankshaft rotation on all cast iron velvet drive transmission except 1:91 and 1:88 reductions.

Good point on the gear ratios. Whatever you choose, be sure you can live with the gear ratio for it's very hard to make up with the prop what you loose with the wrong gear ratio in the trans.

Jeff.

Thanks for the input fellas. Sounds like a 71c should work for me. EW thanks for the offer, and I'll keep it in mind as I poke around for an engine. I'm looking for 1:1 ratio, as I see no reason a 350 would have any trouble pushing a Sportsman.

There is a 71c near me on Clist for $250. Looks like it's in decent shape, aside from missing the dipstick. Think that's a fair price?

http://maine.craigslist.org/bpo/5840620050.html

Joe

I dunno...That dipstick cost me a pretty penny!

Sure.

Jeff

You mean dumb stick
bill

Especially dumb if you don't know to unscrew it, not just rip it outta there and bugger up the rubber seal!

Doh!

Jeff

Joefuskie wrote:Thanks for the input fellas. Sounds like a 71c should work for me. EW thanks for the offer, and I'll keep it in mind as I poke around for an engine. I'm looking for 1:1 ratio, as I see no reason a 350 would have any trouble pushing a Sportsman.

There is a 71c near me on Clist for $250. Looks like it's in decent shape, aside from missing the dipstick. Think that's a fair price?

http://maine.craigslist.org/bpo/5840620050.html

Joe

Not a bad price, plus you could probably sell the Ford mounting hardware (flywheel, bellhousing, spacer) that comes with it and recoup $100 or so. If you go to check it out, see if there is any fluid in it. Even if it has been drained and you have to tip it on its side and poor what little bit remains, try to look at a sample. That will be your best indicator of the condition. If it is clean red fluid, or slightly darkened, you are probably looking at a unit that is in good shape. The darker it is, and/or worse it smells, the closer it is to a rebuild. Keep in mind that these are not expensive to rebuild and you may be able to talk them down if the fluid is burned.
Good luck!

Fastjeff wrote:Especially dumb if you don't know to unscrew it, not just rip it outta there and bugger up the rubber seal!

Doh!

Jeff

It's just like a Thermos stopper. If you remember the Thermos in your lunch box. A long time ago.