Prop Hub Question

Neighbor had a merc hub prop I wanted to test out on my boat(yamaha). My stock power tech is a 13" 19 pitch, this it a 13 3/4 15 pitch solas titan, but has mercury hub. It will fit the spline patter, but i want to make sure I have the right thrust washer and all. Little gun shy to try something on a high dollar engine and risk screwing it up. Should I just replace with a yamaha hub and get the proper thrust washer and all? That's what Im leaning towards just to make sure its all correct, but I know less than nothing about props. Some have told me its fine to run, but its not their boat and I want to do it the right way. Any input appreciated

I thought Yamaha and Merc are interchangeable. I have a 19 4 blade you can try


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Is that a 115 in your boat???


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Yep, Im just wanting to lift the bow more, that powertech doesn't seem to like to raise the bow much, blows out with minimal trim. 4 blade may be the best way to go. Do I need a merc thrust washer? looks like the face of the merc hub is flush, but the yamaha washer is stepped on the side.

You do know that your top speed will drop and you will increase your rpms by about 800 dropping from a 19 too a 15. How many rpms are you running now? Hole shot with a 15 would be a big increase.

My merc thrush washer is stepped on prop side. I have a 23 pitch I bought from EZ off his Yamaha and ran it for years on my Mercury


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Originally Posted by MO' MONEY

Yep, Im just wanting to lift the bow more, that powertech doesn't seem to like to raise the bow much, blows out with minimal trim. 4 blade may be the best way to go. Do I need a merc thrust washer? looks like the face of the merc hub is flush, but the yamaha washer is stepped on the side.

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You need cup on the prop to raise bow. Rake will push it down


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Originally Posted by slabin

You do know that your top speed will drop and you will increase your rpms by about 800 dropping from a 19 too a 15. How many rpms are you running now? Hole shot with a 15 would be a big increase.

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It will run 6200 and has about 1/2 of the boat still in the water before it blows out as I trim up. I am just testing before I buy to see what changes will come about, but I'm also increasing diameter by 3/4 inch too


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Originally Posted by torch

You need cup on the prop to raise bow. Rake will push it down


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That's what I thought, but it seems like every time I try to find the right prop it's a witch hunt.


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I know I have 4 blade 19 with rake you can try. I just went to a 3 blade 19 with cup and have not run it. This engine is designed to run. 6300 rpm and I am @ 5150


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yea, the 4 blade 19 may be a bit much on this motor. I would like to try the larger diameter lower pitch, but again just my reasoning in my head makes it sound good. Im wrong a lot tho lol

I think that 15p is going to redline quick


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Originally Posted by MO' MONEY

It will run 6200 and has about 1/2 of the boat still in the water before it blows out as I trim up. I am just testing before I buy to see what changes will come about, but I'm also increasing diameter by 3/4 inch too


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Is that a hyper lift hull (pad boat)


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Probably so.

Will the larger diameter not make a difference? Again I know very litttle about props, I know you got plenty of experience with em on your f and f hook issue


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yes it is hyperlift

Diameter matters. But even that larger diameter 15 p is going to raise RPMs about 200 to 250 rpms for each reduction in pitch. 4 pitch reduction is going to raise rpms 800 to 1000 rpms. Theoretically


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Is motor too high on transom. I think a jack plate might solve your issues


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Set back on a jack plate will help a boat that rides on pad


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Got a 6" hydro jack plate


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Go up and down with motor


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All the way down with it unless I can get a lift and take entire jack plate down another mounting hole


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Have read a few other people having lift problems with power techs. It gets the job done, just don't get to utilize the pad on the boat


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Trim motor down till cavitation plate is level and should be even or a little above bottom of boat


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Quote:

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Originally Posted by MO' MONEY

Yep, Im just wanting to lift the bow more, that powertech doesn't seem to like to raise the bow much, blows out with minimal trim. 4 blade may be the best way to go. Do I need a merc thrust washer? looks like the face of the merc hub is flush, but the yamaha washer is stepped on the side.

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4 blade props Lift the transom more. They tend to lift the entire boat up front and back.


BRM

Moved the motor all the way down on the jack plate which required some new holes to mount in. have both props to try out today. Motor had about 1.5" more I could take it down. Like it all the way down, push of a button to raise it.

I bet rev limiter kicks in with 15


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I'm gonna ease into it, never know til I try lol. I can always switch back to the 19 in 3 minutes. I think 17 would be a better pitch to try, but, ain't got one lol


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I could hit about 37 before i got to 6k, gonna spin too high. It got out of the hole like it was on fire. Im still thinking the motor needs to come down another 2" or so. but Im all out of adjustment on my jack plate and motor

The stock 19p ran 41.7 at 5900 rpm. I think that will do for now, the little bit I adjusted it down seemed to help get more of the boat out of the water. Maybe just fill my rear livewell or move my batteries further back to help it out. Not gonna throw money at it since it still runs and handles really well, long as it gets me out on the water and back I can live with it

Raise it up. Never seen a boat take one 2" below the bottom. More cup less pitch in the prop for bow lift. The cup will catch the skinny water when you raise her up. 41-42 on a 20' bay boat with the 115 is not to bad.


BRM

From what I've gathered, It still needs to go down, cavitation plate is still above bottom of hull


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Originally Posted by MO' MONEY

From what I've gathered, It still needs to go down, cavitation plate is still above bottom of hull


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It should be about 3 1/2" above. Hard to get much more than 41-42 with the 115 on a 20'er.


BRM

I may get you to ride in it this weekend and see what's going on. It may be fine, just not trimming as high as I figured it should. Still runs and fishes fine


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Originally Posted by MO' MONEY

From what I've gathered, It still needs to go down, cavitation plate is still above bottom of hull


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I have a cherry picker and tool to hold motor. Let me know it won't take 15 minutes


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May try to do it after this weekend. I can always come back up real easy, flip of a switch


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When on plane trimmed out look over the transom and see where the cav. plate is in relation to the water. It should be skimming the top of the water. Mine was 2" below the water. I raised it 2 holes and went from a 19 to 21 pitch prop.

If you need another opinion, I will be glad to get in the boat with you!

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Originally Posted by wilbur

When on plane trimmed out look over the transom and see where the cav. plate is in relation to the water. It should be skimming the top of the water. Mine was 2" below the water. I raised it 2 holes and went from a 19 to 21 pitch prop.

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Ya know, I started thinking that myself about the 21 pitch today, maybe a little more bite will help it hold on while trimming up. Still moves down the lake good enough. I just like to try different stuff to see if it makes any difference. No complaints but after those winds all day Sunday on Sardis, I wanna be able to get the nose up to stay dry or move the spray line back towards the pad


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