Need prop selection for bigfoot advice please.

[D LOE]

Hello all. My lower unit went out about two months ago (55 mariner marathon) And I got a good deal on a bigfoot lower unit so I decided to buy it. I have the lower unit installed but It did not come with a prop.

Now here's the question. Since my old props obviously won't fit on the bigger shaft, I am trying to figure out which Pitch I need. Since the bigfoot lower unit is 2.3:1 and my old one is 2.0:1, am i going to need to go with a higher pitch to maintain my top speed??

Thanks in advance!!

 

[Silvertip]

Re: Need prop selection for bigfoot advice please.

Yes. Big Foot lower units run a 13-1/4 inch diameter prop. On your 55 HP motor you should look for a 15P if the boat is on the heavy side when loaded or you might get by with a 17P if you run lightly loaded. It all depends on the type of boat. The typical prop for a 75 HP motor (which is what the Big Foot lower unit is really from) is a 19P but that would be a bit too much bit for your engine.

 

[D LOE]

Re: Need prop selection for bigfoot advice please.

Thank you for the reply. My boat is a 1652 flatbottom, I am not sure of the weight but I do have a pretty heavy bowfishing platform, I was getting around 33MPH before I changed the lower unit out. I was running a 13 pitch on my old lower unit if that helps. I do run my boat loaded (with fish and generator) at times but not all of the time...so you think I should go with the 15?

 

[hwsiii]

Re: Need prop selection for bigfoot advice please.

D, you should buy a 15" pith prop in the exat same make and model of prop you had on the boat before, as the hange in gear ratio redued your Shaft RPM and you need more pith to get to the same speed and prop slip.
Here are my numbers so you an see the differnes.


Prop Slip

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[D LOE]

Re: Need prop selection for bigfoot advice please.

Thank you very much sir!

 

[hwsiii]

Re: Need prop selection for bigfoot advice please.

You are very welome D.


H