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white80a

Prop size?

Question

white80a

I have a 150 yamaha vmax with a 14 3/4 x 21 prop my rpms run about 5800 wot was thinking of changing my pitch to a 25 to get a little more top end and maybe bring my rpm down some. Any thoughts?

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dan z

you going to loose a lot of hole shot when stepping up that far.

Is your prop stainless? if not try that route first as aluminium gives a little bit of flex...

search the topic at the left and see what other people have done as its talked about alot on here....

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harvey lee

I would give Soderblooms a call as they do some high quality prop work and they know thier stuff.

I had some issues with my hole shot with 3-4 in the boat ans they reworked the pitch on the prop and did a few other things and it works awesome now. I could not purchase a prop the way this one is designed and rebuilt.

I would shoot them a call and explain your issues and I am sure they would have some great suggestions.

Pretty sure they are located in Cromwell, Mn. You can find them on google.

Ask for Jay.

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white80a

i think my hole shot is really good, i have a hydrafoil fin works great. my prop is stainless steel. harvey lee how do they rework the pitch? thay must bend it some how? waht would be the mph differance by going up to 23 or 25 pitch. see i need to get a spare prop so this is why i'm thinking of uping my pitch

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Fish&Fowl

A 25 pitch prop, depending on your boat, would likely make your boat take forever to plane off, if at all. I've never heard of anyone running that high of a pitch for an outboard. And you can't change the pitch of a prop, you need a different one. I would say a 19 to 21 pitch covers most fishing boat applications, but if you decide to go higher and you have a 21 pitch you want to sell let me know!

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hydro

What kind of boat do you have and what is your current top speed? Those numbers are needed to basleine the boat's current performance. My bet is that you would actually lose top end speed jumping up to a 25" pitch since the engine does not have enough torque to spin it.

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Kyhl

Also find out where your optimum operating RPM range is and aim for the top of that range.

A general rule of thumb is that every two inches of pitch takes of about 300-400 rpm. This will vary by application but it's a good ball park.

Dropping down to 5,000 rpm might make your boat bog down.

As mentioned, call Jay. He can make changes to your prop if necessary. He double cupped my prop in the off season and that took off about 200 rpm without changing the hole shot.

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white80a

It's a 1775 Lund pro v current top speed is about 47mph

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hydro

It's a 1775 Lund pro v current top speed is about 47mph

I would say that you are probably at the maximum you will see for top end speed with that motor on that boat. A 150 HP motor will not spin a 25" prop and be able to maintain RPM on a water displacing V hull load like the Lund bottom design. If you are looking to experiment with props, see if you can test run a 19" or 21" pitch 4 blade and see what it does for hole shot and load carrying capacity. It may work very well on that hull.

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white80a

I just looked up my engine specs and it said 5500 rpm is max and my rpm gauge says I'm at 5800 what if I went to a 23 pitch would that be better mite drop my rpm enough

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Kyhl

Call Jay on Monday. laugh

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harvey lee

A 25 pitch prop, depending on your boat, would likely make your boat take forever to plane off, if at all. I've never heard of anyone running that high of a pitch for an outboard. And you can't change the pitch of a prop, you need a different one. I would say a 19 to 21 pitch covers most fishing boat applications, but if you decide to go higher and you have a 21 pitch you want to sell let me know!

If you go to Soderbloom's website, you will see they do this for a fee. I had mine done and it does give me a better hole shot.

here is a paragraph from another website that says you can change the pitch a little bit. Did not want to post the link and break forum policy.

"In the past a propeller could often be repaired by welding, heating, beating and bending it back into shape in cases of light to mild damage. A skilled prop shop could do this once or twice before the prop had to be tossed. Wile they were at it they could change the pitch of the prop a little as well. The costs weren't as much as a new prop, but you'd have to send it out, wait and pay shipping there and back if you didn't have a local shop."

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harvey lee

i think my hole shot is really good, i have a hydrafoil fin works great. my prop is stainless steel. harvey lee how do they rework the pitch? thay must bend it some how? waht would be the mph differance by going up to 23 or 25 pitch. see i need to get a spare prop so this is why i'm thinking of uping my pitch

I have no idea how they do it. I would call Jay and explain what you have and what you would like to see different and see what he suggests.

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