Yamaha question

[lizbeth]

I don't have a clue here: i have a 16' boat, with a 1993 55 Yamaha, now i don't know what size prop is on there now, but i will check when i get home today. my question is if it is a 15, then that means faster at top speed, and if it is a 13 then it should plain out faster ? can someone tell me what i should have on this size boat ? I think i need a bigger motor, cause i think it takes too long to get on plain. i have a Bob's stablizer. also what does a 4 blade do compared to a three blade ?

[Chill-N-Grill]

4 blade gives you a better hole shot but you loose a little top end

[lizbeth]

so if i wanted to get on plain, then i should look at a 4 blade prop ? what size ?

[Chill-N-Grill]

That I can't help you with. Call Mikes Marine they can help or Parkway marine

[Speedy]

Hello lizbeth,

Here is how the correct selection of propellers goes. Your engine/boat needs to get the correct pitch propeller in order to operate correctly. So what is pitch? Pitch is the theoretical distance that one blade of the propeller moves in one complete rotation. Therefore, a 15" pitch prop moves 15 inches in distance. This does not account for slip, which is about 10-15%, in most cases. But that's another story. Anyway, in order to determine the correct pitch for your complete boat/engine you need to account for the entire weight of the boat. The lighter the boat, the more pitch. The heavier the boat, the less pitch. Your target is to hit the recommended engine RPM for a specific model as posted by the manufacturer. In MOST cases the RPM range is 5500 to 6000 at wide open throttle. This does not mean that you must run at that speed all the time. It is only to determine if you have the right prop. But you need to verify this with the manufacturer just to make sure. Just about all the manufacturers post their RPM ranges somewhere on the internet or just call a dealer. You need to hit wide open throttle only to find out if you have the right prop. Now, four blades vs three. Think of it as you going to a swimming pool and running your single hand in the water like a paddle. Then put both hands in the water. One hand pushes LESS water than two hands. The same goes with four blades vs. three. This allows you get on plane much quicker. As mentioned previously the only difference is that you lose a little of the top end speed with a four blade in most cases. Therefore, you need to decide what you prefer. Do you want to get on plane quicker or have a faster top speed? I hope that this info points you in ther right direction. One more thing to keep in mind. If some component such as fuel system, electrical or mechanical is not operating correctly then your max RPM may already be reduced and changing prop pitches does not do you any good.

Speedy

[wevans]

Do you have an RPM gauge on it? WOT is the norm for adjusting pitch. I run a 14 pitch on my 40 Yammy and can't open it all the way up without over-reving the motor but I got a quick hole shot my max RPM is 6000 at WOT, but it's a four stroke, I think a 2 stroke has a lower max RPM. RPMs go up as the pitch goes down and visa-versa

[wevans]

Dang, Speedy lived up to his name

[lizbeth]

thank you all, i will try to find out all the information i need first. like, weight of the boat and recommended engine RPM's.

[wevans]

Looks like between 4500 and 5500 RPMs recommended for yer motor