Propeller pitch / size

[pubertfester]

Hello, have to my yami (F100 detl ) propeller with this specification:
12 5/8 21 K and i go to full throttle with 5400 RpM,
please, need advice to change the propeller - I want a 4 blade propeller ( aluminium ) because my boat is heavy 600 - 700 kg and I want to have more power. what spec should have the 4 blade propeller? it is possible to plane the boat at low Rpm.? now the boat plane on water to 4000 Rpm.
Thanks in advance!!

[TownsendsFJR1300]

Enter your information at this Yamaha website. It'll give you an idea what prop you need and it's performance:

Outboard Performance, Performance Bulletins | Yamaha Outboards

[DennisG01]

Is your engine's MAX RPM rated for 6,000? If so, you can definitely drop down a couple inches in pitch to help your hole shot. Even just staying with a 3-blade will help. Now, one word of caution - if you're running a big load in the boat currently (people, gear, etc) and you drop down in pitch to give a better hole shot, it will also raise your WOT RPM - that's OK - just keep it below the Max spec. HOWEVER, if you run the boat sometime with a LIGHT load, be aware of your throttle so you don't over rev the engine.

Another way to go, and it allows you keep the stock propeller (or still change it if you want to) is to add a set of Smart Tabs. They will make a HUGE difference and give you other benefits, as well. And they usually take no more than an hour to put on.

[Jason2tpa]

The first thing you'll need to do before changing props is find out what your engines spec rpm range is at WOT. You can find this information in your owners manual.

A couple head scratchers came to mind when reading your post. You boat planes at 4000 rpms?? That is a high rpm to get on plane. This sounds like it could be a under powered boat issue, not so much a prop issue. A 100hp engine pushing a 1500lb boat....no matter what pitch prop, number of blades, etc., you're going to continue to have high rpms to get on plane.

A four blade will get you more thrust (not power) and will "grip" the water more than a 3 blade. This is allow you to jump up on plane quicker. However, this is all relative to what I mentioned above. The noticeable difference of 4 blade vs. 3 blade will probably be very little IF the boat is under powered.

What kind of boat do you have your F100 hung on?

[pubertfester]

Thanks for answers!
My engine spec rpm range at wot is 5000-6000 rpm and my wot is 5400rpm with this 21 pitch prop.my wot is good?
Yes my boat i presume is a little bit heavy (700kg 1500lb-1550lb) and the hull is in V,
And to the backside have the heaviest thinks( gasoline 50-70liter) and 70 amp battery, and 50 amp battery( the twenty battery -backup).no other place to put .
when i go i put engine in 4000rpm to plane and after plane i reduce 100rpm to stay on plane . My purpose is to stay on plane in 3500 rpm .
If i go with 4200 4500 rpm is no prob. Plane is good and speed also. But if i reducing under 4000 rpm is difficult to stai on plane. Have to the engine a hydrofoil
Thanks.

[rodbolt17]

to get what you want your simply going to have to get a bigger engine.

but you do need to prop it so it can turn 5800-6000.

trim tabs may help a bit but they also require more power when you tab down due to water drag.

[pubertfester]

Rodbolt17 please tell me what is the best rpm at wot for me? Thanks!

[rodbolt17]

5800-6000 RPM is what your shooting for with that days load.
we had an F150 detonate the pistons some years back.
when we rigged and seatrialed it had a center console,cooler seat and 18 gal gas tank.

when we got it back in it had a 25 gal tank and 18gal water tank and seating for 16 and a ski tow pole.
all with the same prop.
lugging the motor wiped 3 pistons.