Ford 302...21 foot fiberglass with cuddy

[Jakem]

I have recently installed a new engine and took it out...wot is about 3500 rpm and slow out of the hole to get on plane...my prop is a 14x19p 3 blade aluminum...it was suggested I drop pitch...16 was the suggested. Any thoughts or is that right

 

[Bondo]

Ayuh,..... What ratio drive,..?? You got that V8 Ford, right,..??
351, or 302,..?? 2bbl. or 4bbl. carb,..??
How big/ heavy is the hull,..??

You might have to go all the way to a 15" prop, or lower gears in the drive,....
Or,..... yer motor is under-performin',.......

 

[Jakem]

2 barrel 302. Not sure of gear ratio..it is an mc-1..no idea what it weighs either. It's a good size boat.

 

[Jakem]

It isn't extremely slow to get on plane but doesn't seam fast enough to me..I don't care about top speed...I only fish with it so

 

[Bondo]

Ayuh,.... The motor still has to be able to spin it at 4200 to 4800, or yer luggin' the motor, at all rpms, which induces detonation, which burns holes in pistons,....

 

[Scott06]

as bondo said between the drive ratio and the prop you should be able to get it to a much higher rpm. If you dropped to a 15 youd likely see 4300 rpm or so.
since this is newly assembled id verify your tach vs a shop tach, make sure you are getting full ignition advance, and read the plugs to see that you are not lean.
ideally try to find out what your ratio is as it is possible you have the wrong ratio

 

[Jakem]

So in your opinion what should I drop to

 

[Scott06]

So in your opinion what should I drop to

as stated a 15, but that is so low in pitch and you would barely be getting into proper rpm it makes me think there may be others issues as well.. . Like wrong drive ratio.
i would also take the other steps to ensure your tach is accurate and engine is in good tune, unless you already have

 

[Jakem]

My tach has a fluctuation..slight but it's there....I will buy a new one as I'm going to replace them all anyways..

 

[Jakem]

I will also get a 15p...I am having a professional fine tune the engine

 

[Scott06]

I will also get a 15p...I am having a professional fine tune the engine

I would do the tune and verify the tach first then see where it lands wot rpm wise Before buying a prop.

 

[Jakem]

Will do thanks fellows

 

[Jakem]

I went to a 4 blade 14.5x 17p. It raised my rpm to 4100 ish rpm wot...shall I drop again

 

[Jakem]

As for full advance on the timing is that best done in the water or muffler. It is set to 10 btdc now and I am going out tomorrow and could check.

 

[Jakem]

These came with the petronix ignition

 

[Jakem]

These came with the petronix ignition

 

[Jakem]

The springs it came with are silver...so the squares

 

[Scott06]

So with 10 degrees initial plus the 24 centrifugal you should see 34 degrees total advance by 3500 rpm or so. You can check this on the muffs just briefly rev it. especially with an older mechanical advance distributor that can get hung up or corroded, you just want to verify you Are getting advance otherwise you wont make full power.

if yiu are confident in the tune and tach accuracy, then yes i would drop to a 15 to get revs up to 4500 or so. Not that you have to run it wot but the fact that it is properly pitched so it can reach wot is the important part.

 

[Jakem]

Gotcha...thank you

 

[Jakem]

Shall I get a 4 blade 15 or a 3 is my only other question on this topic