Prop
 

ok so I have a new boat, used but new to me, I am running wide open 5100 RPM the boat is 15ft 54inch custom V 1/8" alum. Guy I bought from had 60 2 stroke Yamaha, I have 50 s stroke Yamaha running 10.5 x 14 prop. If I put my old jack plate I'm thinking I should pick up 200 RPM or so? Operating range is 4500-5500 but I know to get best performance and longevity it should run full RPM wide open. any of you guys can give me input? prop shop says I need to go down a pitch but says I'll lose 2-3mph so if I can pick motor up and gain the RPM I need I should get 2-3 MPH... Just guessing any info would be nice. GPS reading is 35.5MPH which is not bad but I want optimal performance.

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Play with your jackplate. If you can get it to turn 5300 right now in the heat of the summer you should be good . When cool weather comes you will be at 5500 or banging the rev limiter. Overall , 5100 for the temps now aint bad.

Is it a 2 stroke or 4 stroke?

The rev limiter on a 50hp 2 stroke Yamaha is 5800 rpm, the rev limiter on a 50hp 4 stroke Yamaha is at 6250 rpm.
That 2 stroke motor makes max horsepower and torque as close to that 5800 as you can get and the 4 stroke makes max hp and torque at 6249 rpm.
You are pushing a very heavy hull. You may turn a 14 pitch, just won't turn it efficiently, it will lug the motor.
You can prop the motor for an empty boat or a loaded boat, not both with the same prop.
We run 13 pitch Turbo Hot Shots on 50hp hot rod Tohatsu's, same gear ratio, and turn them about 6200 rpm on a loaded boat. They run in the low to mid 40's with a hunting load.
Again, do you want to prop it for the 2% of the time you will run totally empty or the 98% of the time you will run loaded?
If you're turning a 14 pitch 5100 empty, you are further off than 1" of pitch on a loaded boat.
D

It's a 2 stroke and I'm puttting my jackplate today, yes the boat is 15 ft 5 in x 54 in all .125" 11 degree at bow and 6 degree at stern although it has 12in pad. I have a buddy that has a boat shop and tons of props that fit my motor from 12 pitch to 17 i can use them as needed to test it, i'm thinking lifting it will help quite a bit we shall see, I do appreciate all the feed back i just don't want to lose any speed, i knew getting this would sacrafice some i was crusing at 36 on flat about 4700 rpm right now WOT is 36 at 5100, thats full load on light load i get 5500.

here's the rig

Hard to tell from the trim angle but you will benefit from the jack plate no doubt. Need to get those rpm's up to get the max power out of that motor. Who built that boat?

Eric Romero. He's off 90 near Lydia. The boat has 12" pad I put jack plate on today and it was set at 4" above bottom I couldn't get trim without it cavatating I'm gonna drop it 1" and see that would set me 3" where it was 1 5/8" when mounted flat on transom go half inch down from there and so on if needed.

Need some racing stripes on dat ting.

Camouflage so I can't be seen... Lol

Prop
 

So I have my motor 5" setback and 2 1/4" above keel it's jumping up riding level at 3/4 trim she wants to cavitate. When trimmed I held 5480 RPM 37.6 mph. Should I drop it half inch to get full trim or should I leave it? I had full ice chest, full drink chest and 15 gallons of fuel. Pretty much full load.

I would try dropping it and see what happens....you can always go back up that is the beauty of a jack plate. That is impressive numbers for a 50 on a heavy boat. I have a 15 foot duracraft with a 70 johnson. On a good day it gets 42 mph @ 5,500 rpm's

I agree with Montauk. Plus it gives you room in your trim for when you have a buddy with you or a heavier load.

That's what I was thinking. It was leaning to my side trimmed down but as I trimmed it leveled off and held pretty good. I'm thinking the half inch will give me full trim if not real close. And should still get the RPM's. but I'm liking this boat more and more.

If you can get a pic of the pad I would like to see the design. Don't see too many boats that size with a pad.

Prop
 

Never seen a pad designed like that before....does it chine walk at all?

It didn't rock one bit. I was really impressed I knew his boats performed pretty good but with a 50 I wasn't expecting to get this. But I'm not gonna complain.

I liked the way the inside of the boat was laid out when i saw it. Looked like there was a lot of room for the size of the boat. I guess since there wasn't a rear bench seat like most factory built boats.