F 36 prop size

[BSpencer]

I'll apologize up front for interrupting this conversation with a new topic (or at least different stats). I have a 1989 F36 sportfish with twin crusader 454's. The old owner put 4 blade props on the boat and the performance is suffering greatly. PROWLERFISH: Can you tell me the correct prop size and pitch for that boat? Do you have a performance chart (RPM / Speed / GPH / etc.) that you could post? If it's any easier to email, my address is ng.billspencer@gmail.com

[prowlersfish]

I'll apologize up front for interrupting this conversation with a new topic (or at least different stats). I have a 1989 F36 sportfish with twin crusader 454's. The old owner put 4 blade props on the boat and the performance is suffering greatly. PROWLERFISH: Can you tell me the correct prop size and pitch for that boat? Do you have a performance chart (RPM / Speed / GPH / etc.) that you could post? If it's any easier to email, my address is ng.billspencer@gmail.com

Factory props were 20x21 3blade cupped But many have gone to 20x20 3 blade,
Here is one user's data Below ( Thank you, Mitch)
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Unread post by LandVF36 » Thu Nov 12, 2015 10:39 pm

I have a F36 Sportfish. She has 330HP GM 454s spinning 20x20 3 blade props (at least that is what they are marked). Back in 2010, I had just installed fuel flow meters and posted this data:
RPM /MPG /MPH /Port GPH /Starb GPH /Total GPH
750 /1.63 /4.74 /1.3 /1.6 /2.9
1000 /1.69 /5.75 /1.4 /2 /3.4
1250 /1.44 /7.78 /2.6 /2.8 /5.4
1500 /1.36 /8.7 /3.4 /3 /6.4
1750 /1.18 /10 /4.9 /3.6 /8.5
2000 /1.13 /10.8 /5.1 /4.5 /9.6
2250 /0.95 /11.3 /6.9 /5 /11.9
2500 /0.74 /12.8 /9.2 /8 /17.2
2750 /0.88 /17.6 /10 /10 /20
3000 /0.74 /21.3 /16 /12.9 /28.9
3250 /0.75 /26.5 /18.5 /17 /35.5
3500 /0.75 /30 /18.6 /21.4 /40
....................................................................................................
I should note the 1989 spec sheet from Trojan lists slightly lower speeds at the same rpm. With a top speed of 34 mph 4300 rpm and 54 GPH

[BSpencer]

Thank you Prowlerfish! This is incredibly helpful. Do you happen to know the shaft size on that boat so that I can begin looking for replacements? Is it 1.125"?

[prowlersfish]

Shaft is 1 3/8"

[Moderator]

I made this a new topic. So no confusion w/tri cabins

[BSpencer]

Thank you PROWLERFISH. This is incredibly helpful. I'm grateful for guys like you who help out newbies like me! Have a great day!