repowering/silverton 34ft,1980

[eddy pons]

looking for the right answer,however wild it might sound,,,have a 1980 34ft silverton sport/fish a (slug),,,we want to repower? We are considering crusaders 5.7mpi or, 6.0 mpi,,OOOps I forgot to mention,(slug) is powered by no less than chrysler small block, 250hp, coupled to borg warner--walters V-drive,,,ratio 1.5:1,,,my problem is ,If we decide to go with the 6.0 we know we have to replace the trainnys,,we are good with that,but what kind of a pain will it be to couple this new transV-drive since the shaft now enters thru it?We are also considering changing ratio to 2:1, we feel by doing this we could swing a bigger prop,thus more speed ,better fuel economy,,If anyone out there has done something like this I would apreciate the help,,,,Eddy

 

[Bondo]

Re: repowering/silverton 34ft,1980

Ayuh,......

I'd think a 34'er is a prime canidate for a Big Block or even a Diesel......

We are also considering changing ratio to 2:1, we feel by doing this we could swing a bigger prop,thus more speed ,better fuel economy,

I might be Wrong here,....
But that sure sounds like you're gonna $pend a ton of Money going around in an Expen$ive circle.......

 

[QC]

Re: repowering/silverton 34ft,1980

I struggled at first too Bondo, but it's twins . . .

 

[tommays]

Re: repowering/silverton 34ft,1980

I think one of your OLD motors would have been reverse rotation WHICH are no longer made so you may be running into some transmission issues no mater what

Tommays

 

[Don S]

Re: repowering/silverton 34ft,1980

You are obviously not understanding how engine torque, HP, gear ratios, prop sizes all work together.
You can't just change out a gear ration and go to a bigger prop. It would be so out of the normal optimum running sizes of the prop that it would be worse than when you started.
Use the recommended gear ratios, and prop sizes for the new engines. Trust me, Even with twins, a 5.7 or 6.0 is still a small block and in a 34' boat, it's still going to be a slug. A little quicker out of the hole, but not by much.

 

[arks]

Re: repowering/silverton 34ft,1980

looking for the right answer,however wild it might sound,,,We are also considering changing ratio to 2:1, we feel by doing this we could swing a bigger prop,thus more speed ,better fuel economy,,If anyone out there has done something like this I would apreciate the help,,,,Eddy

IMO you'd be better off keeping the original ratios and running gear. As these guys said, if you fool with it you could burn a whole lot of green and still not be happy. Your Silverton will never be a speedboat........
Why not drop in a couple injected smallblocks? They'll have more HP than the Chryslers and weigh less. Props can be changed or cupped for better performance, too. Don't forget trim tabs. The new Steyr diesels could be an interesting setup but you'd be spending at least double compared to gas. If you're actually serious about spending that kind of money on a 28 year old boat, maybe you should go buy a different boat!

 

[eddy pons]

Re: repowering/silverton 34ft,1980

The problem we are having is ,that if we go the big block way,yes its better,but not cost effective,the boat is definitely too old,,,I priced 6.0MPI 370hp with trans V-drives @ around 12k each, thats 24k combined,we are doing the instalation ourself wich makes it a bit cost effective,,,the boats option new where 454cui which were rated @ 330hp,,,even if we spend 26k when we are done we could not replace such a boat,we just are not sure if we would be able to align these motors and trans,,we are hoping that the weight we save with the small blocks will take up the difference we lose of torque by not going big block,,,I cant find a graph to compare power and torque curbs @ a given RPM so we can compare the motors,,,thanks for the help guys, keep them coming,,,,

 

[eddy pons]

Re: repowering/silverton 34ft,1980

Many years ago we did a similar job with a wellcraft,it was a 30 or 32 footer,another led sled from the 80's,,,big cabin,merc inboards 260hp with borg warner V-drives 1.5:1,,the boat's top speed was 18mph @ around 4200rpms,,,we built chevy 400 cui,stroked to 383,fresh water cooled, and swaped the gear ratio to 2:1,the props had to be replace,at the end the boat acted as a totally different boat, we were able to get nearly 31mph given the water was flat,We know thats not the case with this silverton but we might be willing to take the chance that this boat has to run a lot better with new iron in it,,diesel is aways better but we dont have pockets that deep,,,

 

[TilliamWe]

Re: repowering/silverton 34ft,1980

I was told by a marine mechanic when i looked at a 1980 Silverton 31 sedan with twin Chrysler 318s that the real issue would be replacing those v-drives. He told me that the new v-drives are longer and to be certain that there was nothing in the way should I need to replace them. Not sure if that's an issue for you, but something else to consider.
Man that's a lot of money to spend on a big old boat. Hope it's in perfect shape.

 

[rodbolt]

Re: repowering/silverton 34ft,1980

why anyone would destroke a 400 to 383 is way beyond me, its simply going backwards.
however, for many many years the velvet drive clutches could have the input rotation changed.
a call to borg warner(actually now its Hurth) with the clutch seriel number may help
the BW/Walther V drive as been around forever.
had a customer with a 33 wellcraft St Tropez that had that setup infront of a pair of MIE 454 engines.