OMC 4.3 to 5.7 worth it?

[Lakes84]

Would it be feasible to put a 5.7 engine into a 21 foot boat that had a 4.3 with the OMC Cobra outdrive? I understand the gear ratio differences, but not educated enough on the subject to know if it would work correctly. I've read where a prop change would/could bring the motor to the correct WOT RPM's.....thoughts? Thanks! -Joe

 

[Bondo]

Re: OMC 4.3 to 5.7 worth it?

Would it be feasible to put a 5.7 engine into a 21 foot boat that had a 4.3 with the OMC Cobra outdrive? I understand the gear ratio differences, but not educated enough on the subject to know if it would work correctly. I've read where a prop change would/could bring the motor to the correct WOT RPM's.....thoughts? Thanks! -Joe

Ayuh,.... Odds are, you'll never find a prop Big enough to compensate...

 

[Lakes84]

Re: OMC 4.3 to 5.7 worth it?

OK thanks, so I take it that a gear change wouldn't be feasible then? Would this be the same scenario with a 5.0?

 

[Bondo]

Re: OMC 4.3 to 5.7 worth it?

OK thanks, so I take it that a gear change wouldn't be feasible then? Would this be the same scenario with a 5.0?

Ayuh,... same story,... If yer gonna go through all that,...

Dump Everything OMC, 'n drop in a Mercruiser... atleast there's more, 'n cheaper parts around...

 

[Lakes84]

Re: OMC 4.3 to 5.7 worth it?

Ayuh,... same story,... If yer gonna go through all that,...

Dump Everything OMC, 'n drop in a Mercruiser... atleast there's more, 'n cheaper parts around...

I was afraid you were going to say that LOL. I just dropped 7700.00 for a new motor and that's not installed yet.

I have the chance to move up to a 5.7 from the 4.3 since the motor won't ship till Monday. Not sure the performance difference would be enough to be financially feasable to put a 5.7 in AND a new out drive...After all it's a 87 Sport Craft hull. A mint condition hull with no rot, but still an 87 hull.

Thanks for the advice -Joe

 

[Levinz11]

Re: OMC 4.3 to 5.7 worth it?

Did you mean $770?

 

[Bondo]

Re: OMC 4.3 to 5.7 worth it?

I was afraid you were going to say that LOL. I just dropped 7700.00 for a new motor and that's not installed yet.

I have the chance to move up to a 5.7 from the 4.3 since the motor won't ship till Monday. Not sure the performance difference would be enough to be financially feasable to put a 5.7 in AND a new out drive...After all it's a 87 Sport Craft hull. A mint condition hull with no rot, but still an 87 hull.

Thanks for the advice -Joe

Huh,..??..??

 

[Lakes84]

Re: OMC 4.3 to 5.7 worth it?

LOL, My old motor was a goner. I purchased a 100% new turn key motor, with everything on it, to include a full cooling kit. Shipped to my mechanic that was 7700.00... brand new crate vortec 4.3 made in Michigan by GM. I had the money and knew I wanted new after reading plenty on rebuilds.

I work on computer networks, not motors lol, so I wanted the best. The folks at Michigan Motorz have been super awesome to work with. There was an issue with one of their suppliers that got me thinking about the 5.7 ( I could get it much quicker) Any way, I boat on the Canadian border, so I no joke wanted the best money could buy. The Cobra outdrive still works great, no leaks or hard clunks, So I guess I'll just have the 4.3 sent out and be happy with what I have. Thanks. -Joe

 

[bruceb58]

Re: OMC 4.3 to 5.7 worth it?

Yikes, I think I would have spent that kind of money on a different boat with a Volvo or Mercruiser.

 

[Lakes84]

Re: OMC 4.3 to 5.7 worth it?

Yikes, I think I would have spent that kind of money on a different boat with a Volvo or Mercruiser.

I see your point. Already thought about that and did my share of looking....trust me! I was looking for a Sport Craft or Thompson Hull for around 10K

My issue is, when buying something at around the 10k price in a popular hull, if they're any good they are sold FAST. Then, if you do buy something without a survey, you might be back at square one. I'm looking at the 21 ft cuddy's as that's what I own.

We are huge walleye down riggers and that's the type of boat that suits us best and are extremely hard to find in good condition at my price point. At least now I know the boat is solid with a solid motor. Not sure what it will be worth, but one just like mine sold in Warroad Mn for 11K and that wasn't close to as nice as mine. Mine is a perfect condition Sport Craft with the original finish on all of the wood still and an aluminum trailer to boot. To me, knowing what I have is worth WAY more than buying a potential money pit. -Joe

 

[bruceb58]

Re: OMC 4.3 to 5.7 worth it?

The biggest problem I see is that you will still have an OMC Cobra on it.

 

[Lakes84]

Re: OMC 4.3 to 5.7 worth it?

The biggest problem I see is that you will still have an OMC Cobra on it.

100% agree with you there. I'm thinking about a move to a Volvo SX drive or a Bravo drive this winter, used of course. Selling all of my Cobra stuff should net me some extra $$ to off set that cost......A little at a time.....