More pitch or bigger diameter?

5150abf

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Aug 12, 2007
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5,808
2018 F50 on a 16' aluminum fishing boat.

Been playing with engine height, started on the second hole, I am on the 4th hole up now, I run a 6'' setback, still doesn't blow out at full trim and got to 30.5 before I pulled the throttle back because it was spinning 6200 and climbing slowly.

I am running an 11x11 prop and on the 3rd hole it was right at 6000 and 30mph so I need to drop rpm by 500 or so.

Better to go bigger pitch or a bigger diameter?
 

5150abf

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5,808
I have, that is how I got the prop I have, thought I nailed it until I started raising the engine.

first time out on the second hole I was at 5800, went up to third hole got to 6000, went up to the fourth hole and now I am over 6000.
 

99yam40

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Sep 7, 2008
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8,851
16' aluminum fishing boat does not tell much
Do you have a pocket or tunnel?
Jack plate might help if you do.
did you try turning any when trimmed up like that?
need to make sure it does not blow out too

Was speed dropping when RPM was going up any
was it loaded close to the way you will be normally running
 

5150abf

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16'v hull, full floor and 2 casting decks all 3/4 marine ply fairly heavy I would say and no, it defiantly wasn't blowing out and was continuing to go faster., didn't jump rpm like I trimmed to much, did that a bunch with the old engine so know what to look for there.

No tunnel, just the 6'' setback and normal load.

Didn't care for it that close to redline anyhow.

I am really happy with the new engine, old one would once in a while hit 28, new one consistently runs just a tick over 30, with with the right prop I can be at 32 I think but mostly want o get it away from redline whatever speed that works out too.
 

Silvertip

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Sep 22, 2003
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28,758
Your boat has a throttle. Pull it back a little and when loaded heavy, the prop you have will be beneficial in getting out of the hole.
 

5150abf

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Aug 12, 2007
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5,808
Just got off the prop finder and I have a choice between a 10.375x 13 or a 11.125x 13, I am leaning towards the 11 1/8x13.

I am thinking that will get me closer to 5500rpm- 5800rpm, 400 rpm for the bigger pitch and a couple for diameter increase.

Any thoughts?

Again it is 30 degrees out and won't have her out for another 3 months at least so no rush to order anything
 

5150abf

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Aug 12, 2007
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5,808
I got the size off the Yamaha prop selector for my engine so I would assume it will fit, I have at least 1 1/4'' clearance with current prop.
 
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