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TOPIC: 2556 - Alpha Drive Owners, please confirm RPM VS. Speed

2556 - Alpha Drive Owners, please confirm RPM VS. Speed 06 Oct 2017 07:21 #26

  • Zarn
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Mercury website has a prop caulater you need to know weight of boat to give you a good starting point every 1 inch pitch change =200rpm. On another point research original weight of your boat and learn the true weight of your boat now if it's much heavier you might have a water logged hull.

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Daniel Drummond.
Waitakere Auckland.
New Zealand.
2252 Hard Top.
Carbed 5.7 alpha one.

2556 - Alpha Drive Owners, please confirm RPM VS. Speed 06 Oct 2017 14:09 #27

  • Northern Bayliner
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I have a 2002 2452 (242) with the 5.0L 2bbl (carb) Alpha 1 Gen2 with 1:62 and a 16x16 alum Prop. I cruise at 26mph at 3700-3900 rpm. +- 200 rpm. I hope this helps you.

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2556 - Alpha Drive Owners, please confirm RPM VS. Speed 06 Oct 2017 15:18 #28

  • builderdude
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Don't think it'd be a water logged hull, there's no core material in the hull except for the structure in the transom and stringers. Don't think it'd even equate to a full tank of potable water (35 gallons + another 6 in the water heater)

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Dave
Edmonds, WA
"THE FIX"
'93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
.030 over-Vortec top end-part closed cooled
***The rebuild of my 2556***
www.baylinerownersclub.org/index.php/for...ansom-repair-my-2556

2556 - Alpha Drive Owners, please confirm RPM VS. Speed 07 Oct 2017 20:12 #29

  • builderdude
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Landin wrote: Hi Dave,

Yes a project, but was operational when I first bought it .. because it was an older engine and this was my first ocean vessel, I never opened it wide open and got such a good deal on it an ocean trial was not required...

What would your first move be ?

A) replace the 15 × 15p prop that's on the boat now to ensure there is no flex/ its a very old prop

B) try a 14 × 14p prop

C) try a 13 x 13p prop

D) new transom assembly and find a good / used bravo drive? $$$$$$$$

On goes the journey...

Next week, I'm gonna reach out to Mercury and see what thay advise.....this just all seems so strange....

THX!!!!


For now I'd assume the current drive ratio and prop diameter/pitch are correct for your boat (Joon verified earlier & I think he'd know) so before changing anything there I'd probably ensure the engine is performing as it should.
I know this engine is new and shouldn't have any issues, but Id compression test it to verify things in the cumbustion chamber are as they should be. Double check the ignition base timing, the advance curve and the total advance. Was the fuel tank replaced or cleaned out during the repower? Verify fuel delivery is not an issue, as in no gunk in the fuel tank, anti siphon valve is not causing restrictions, dip tube screen is not plugging up, fuel lines and fuel/water separator is all new, all the way up to the new carburetor. Higher engine rpm up on plane (heavy engine load) is where all these things can cause issues.
If all that stuff checks out then I'd move to the prop. There are good prop shops in my area that would let you test props if your purchasing one from them but I'm not sure if you have that option where your located.

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Dave
Edmonds, WA
"THE FIX"
'93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
.030 over-Vortec top end-part closed cooled
***The rebuild of my 2556***
www.baylinerownersclub.org/index.php/for...ansom-repair-my-2556
Last Edit: by builderdude.

2556 - Alpha Drive Owners, please confirm RPM VS. Speed 07 Oct 2017 20:50 #30

  • MadWill
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A 13inch diameter prop isnt going to give you the thrust you need to get on the plane. I would also be doubtfull of the 14inch diameter.

Look at the Enertia props, go up in diameter as they drop pitch. The 15 x 15P or the 15.2 x 14P would be a good place to start IMO.

If you are in the US, get in touch with Ken from Prop Gods, they will allow trial and return for a small fee. Very knowledgeable about props also. He helped me when changing from a 1.62 rato to a 1.47

The best option, if cost isnt an issue, is a Bravo drive.

Cheers Adam

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2005 Trophy 2352 WA
Mercruiser 350 MPI
Located in Brisbane QLD, Australia
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