Prop Size ?

[bentpole]

Can any of you tell me if there is a web site I can go to that will tell me what size of prop I need? I had a 30 hp yamaha on my boat changed it over to a 40 yamaha,It don't seem as fast as my 30 & LOVES the gas,I use to could fish 2 days on a tank of gas. now I'll do good to make it a full day on the same tank???? Was told it may need a diff- size prop.

[must buy my fish]

What size is on it now? I have a merc. 30 hp with a 13 pitch prop .If you get too much pitch it can cause overheating & lugs your motor too much.

[papasage]

try this site .
http://www.themarinedoctor.com/cgi-bin/YaBB.pl

[drill instructor]

be very carefull going to a bigger prop. i cracked my gearcase doing just that. I will definetly ask a pro. I sure wish i had asked a mechnic. Boat weight and size has a lot to with.

[Jerry Blake]

Can any of you tell me if there is a web site I can go to that will tell me what size of prop I need? I had a 30 hp yamaha on my boat changed it over to a 40 yamaha,It don't seem as fast as my 30 & LOVES the gas,I use to could fish 2 days on a tank of gas. now I'll do good to make it a full day on the same tank???? Was told it may need a diff- size prop.

Hey bentpole:

It's real important to have the right prop for your set-up. Every boat is different depending on how much weight you carry and how it is distributed in the boat.

Ideally you want to just reach the maximum recommended RPMs for your motor at wide open throttle with a light load. If you can't reach maximum RPMs you have too much pitch and if you reach maximum RPMs below wide open throttle you have too little pitch.

Too much pitch and you're working your motor too hard and too little pitch your wasting horsepower and have the potential of damaging your engine by running at too high of RPMs. Going to a stainless steel prop and having it "tuned" by a prop rebuilder that knows what he is doing will give you more efficiency.

You also want to make sure your motor is installed as high as possible on your transom without causing excess slipage or "ventilation". If you have to raise your motor past horizontal to reach maximum speed at a given throttle position you may want to try raising the motor one or two holes. Throwing up a "Rooster Tail" is real pretty but isn't as efficient as pushing water straight behind you. On the other hand, if you have to keep your motor trimmed below horizontal to keep from slipping then your motor is mounted too high.

[ky-slabseeker]

The biggest thing you want to keep an eye on is your RPM:cool

[Barnacle Bill]

Here is everything you ever wanted to know about a prop. http://boatfix.com/how/props.html

[grubby]

I was told by a reputable dealer here in okla. that you want your prop at only 4 to 6 inches below the bottom of your boat for best fuel economy. rpms are very important to watch. lower number on the pitch gives better hole shot. the higher number gives you top end speed but less hole shot. yamaha should be able to tell you the ideal prop for your boat.

[robbor]

You also want to consider how much you load the boat down and how rough the water normally is. I would not hesitate going 1 or 2 steps faster than factory to a 15-16". Also try not to gun it from a dead stop, just ease it up to speed. I wish I could go 1 day on a tank of gas.

[Marshrat]

Can any of you tell me if there is a web site I can go to that will tell me what size of prop I need? I had a 30 hp yamaha on my boat changed it over to a 40 yamaha,It don't seem as fast as my 30 & LOVES the gas,I use to could fish 2 days on a tank of gas. now I'll do good to make it a full day on the same tank???? Was told it may need a diff- size prop.

Check out this site. You should be able to find what you need, just answer the questions.

http://appcenter.mercurymarine.com/p...jGr5XDqQLvpAe_


Warren