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just a theory 20 Jun 2009 03:35 #1

  • 96bayliner
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I have a '96 2050 with a 4.3L v6/alpha one. I am about to start rebuilding a stock 305 or 350 for it. I have heard that with adding v8 I will have to either get an alpha with a different ratio or have the gears in mine changed. I am currently running a 21 pitch ss prop. Instead of the gear swap couldn't I just run say a 27p prop give or take? Isn't changing the prop doing the same thing in effect as changing the gear, kind of like shorter/taller tires on a car?

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Nick
1996 2050 cz
4.3L alpha 1...looking for a 350:D

just a theory 20 Jun 2009 04:27 #2

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There is a lagre differnece between Props and drive gear ratio.

The wrong lower gear ratio will not match the engine. The prop will allow fine tuning of the engine to make the correct RPM.

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just a theory 20 Jun 2009 12:59 #3

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I'm just speculating here, knowing how most manufacturers like to save money wherever possible, I suspect the higher ratio drives that were designed for 4's and 6's aren't as beefy as the ones matched up to V-8's. The alpha 1 gen 2 housings are the same though so a swap out to 1.5 to 1 or 1.47 to 1 should be simple if you know what you are doing (I don't know how).

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1994 Bayliner/Trophy 2352 w/ factory hardtop
upgraded to 300hp Mercruiser 350 magnum
alpha 1 gen II / 14 3/8x18x4 SS

just a theory 20 Jun 2009 15:21 #4

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96bayliner;312346 wrote: I have a '96 2050 with a 4.3L v6/alpha one. I am about to start rebuilding a stock 305 or 350 for it. I have heard that with adding v8 I will have to either get an alpha with a different ratio or have the gears in mine changed. I am currently running a 21 pitch ss prop. Instead of the gear swap couldn't I just run say a 27p prop give or take? Isn't changing the prop doing the same thing in effect as changing the gear, kind of like shorter/taller tires on a car?


First off, whether M/C, OMC or Volvo........... or even shaft drives, there is usually no substitute for a correct over-all gear ratio.
Gear ratio is always predicated by engine size/torque/hp...... and to a varying degree, elevation/hull size (in some cases)!

While it would seem to make sense like changing wheel/tire size on a vehicle, it does not work with Hydro-propulsion.
Engineers have spent countless hours researching/developing this technoloy.


The rest of the swap is likely doable so long as your hull can accommodate the longer/heavier engine....... It likely will if this boat was at one time available with the 5.0L or 5.7L!

Also, swapping gears is usually cost in-effective when you can sell/buy! IMO.
Gears/bearings and set up time makes this unattractive. Again, IMO.

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Rick E. Portland, Oregon
2850 Bounty Sedan Flybridge model
Twin 270 HP 5.7's w/ Closed Cooling
Volvo Penta DuoProp Drives
Kohler 4 CZ Gen Set

just a theory 20 Jun 2009 16:34 #5

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I would definitely take some measurements and make sure that this motor will fit into the space allowed. I've got a 4.3 in my 1998 2052 FA and can't imagine trying to shoehorn a V8 into the given space.

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Bob Hawes.
Kelowna, B.C.
1998 Trophy 2052 WA
4.3 Vortec, A1 G2

just a theory 20 Jun 2009 17:37 #6

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2850Bounty;312429 wrote: First off, whether M/C, OMC or Volvo........... or even shaft drives, there is usually no substitute for a correct over-all gear ratio.


I am constantly amazed at what a great asset you are to this site. I don't know how you do it, but it takes a lot of time and effort to keep up with all these tech questions and respond with the detail (and patience) that you provide.
Kudos to you Rick....:arr

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2252 Ciera - Sold
12" Sea Nymph

just a theory 20 Jun 2009 17:48 #7

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It's simple! I Google it and then subcontact it out! (You don't think that I really know all this stuff myself, do you?) :D

But I do thank you for those kind words.... glad to help when/where I can.

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Rick E. Portland, Oregon
2850 Bounty Sedan Flybridge model
Twin 270 HP 5.7's w/ Closed Cooling
Volvo Penta DuoProp Drives
Kohler 4 CZ Gen Set

just a theory 21 Jun 2009 14:25 #8

  • 96bayliner
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ok thanks guys. I was just hoping I wouldnt have to change gears. However it can't be too hard, been looking at it in my seloc manual. I have changed countless rear car gears so I think it is doable. The engine will definitly fit, the 4.3 looks tiny in there. And like someone already said, you could get a 305 or 350 from the factory in this boat. I realize that a v8 won't make a ton of difference in my boat but I am a constant tinkerer. I had to replace the 4.3 when i bought the boat so no prob there.

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Nick
1996 2050 cz
4.3L alpha 1...looking for a 350:D
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