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Foil on my boat


MPFit

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Hi guys! I have a hydrofoil on my motor, and I'm not exactly sure why! 2006 Redfisher 18 with the Vmax 150. More than enough power to get on plane and nice speed also. It has a reliance 3 blade on it. I'm far from a prop guru. I asked why he put it on originally and he said he had one on an older boat and it made a world of difference. I'm on plane within seconds with it on, really trying to decide if it's needed or should I take it off? Is it hurting anything? Any input would be great! Boat has trim tabs also; another reason I'm not understanding the inclusion of it! But the boat is great and if it ain't broke don't fix it ya know!?

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I have a similar foil on mine, which was there when I bought it used. I was having my lower unit service done and the guy at my local boat shop said it probably doesn't make a huge difference but won't hurt. He said that if it has trouble getting on plane a better fix is to look at the pitch of the prop. I'm kind of with you though - if it ain't broke, don't fix it! Before you remove it, see if the foil is bolted through the flange or does it just slide over? 

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I'm usually cruising at 28-30 around 4-4100rpm. I'm not a speed demon and haven't went WOT yet. I'm not unhappy with the performance by any means; but as I don't know much about these boats shy of what I've read on here I'm curious if I'm running optimally or poorly. 

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I had an 18RF with the exact same motor. You have the wrong prop on it. I ran a 21 pitch and it was a powertech ofx. Got on plane quick and ran 53-55 mph top end at full rpm. I did add a negative wedge to it which increased the down trim to keep the bow from rising when getting on plane. It was more like a sling shot. Get the right prop and get rid of that hideous hydrafoil the boat does not need it. You have the maximum HP on the back of that sled you should not need that foil.

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The more I think about it, I have some serious stern squat when coming to plane, which takes care of itself quickly. Again I don't struggle at all to get on plane which I attribute to max hp and thrust of the 2 stroke. That being said at 30mph cruising I've had cavitation in long deep turns (not sharp- which I'd assume is worse). I'll look into different props, I'm not a speed junkie but I'm not sold on a 4 blade. If I could fix the stern drop / bow rise a little and get more bite through turns that's a win to me.. as well as ditching the foil. I'll do some research as I've never really looked into props before. Any and all advice is always appreciated!

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With boats everything is a give and take. If you want more bite and a better hole shot then a 4 blade is what you want. You will only loose some top end. With your set up you don't really need the 4 blade if you have the the proper 3 blade you will get a good hole shot and still maintain your top end. When you come on turns just trim down your motor a bit for the bite and then trim back on straight travel. I would install a negative wedge sold by Bob's Machine Shop which will make your boat get on plane like a sling shot as opposed to the typical bow rise you get just before she planes out. I bet with that 17p prop you are reaching max rpm's really quick and not giving your motor a chance for its full potential.

I try to prop my boat to get equal rpm to speed. My current set up gives me 42mph/4200 rpm, 48mph/4800 rpm, 50mph/5000rpm...you get the picture. Contact Marcus/Funky Monkey on this forum he is the prop guru from Powertech props and he will guide you in the right direction.

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Yea, I think your right; boat had a jackplate sticker with no jackplate. I assume he kept some of the items including the prop and threw that on it.. not the end of the world- again the boat rides fine but I'll look into bagging the foil and obtaining a more efficient prop. I'm not too concerned with top end but sharper turns and lower speed plane sounds like a win win for me. That being said I don't want to lose my normal cruising speed of 30mph. Once I can get it in the water I'll do a quick numbers run at WOT with and without trimming it out to see where we stand. I can't find any Yamaha performance numbers for the 150 vmax unfortunately. I did see that stock prop from the dealership should be a 19p prop not this reliance I have- so it was obviously changed out.

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8 hours ago, Moderator said:

I see so many used boats sold with the wrong prop.  Only thing I can figure is that the sellers keep their expensive props and stick on a cheap spare that may or may not be close..

Your Redfisher should be a mid 50's boat.

M-1

Or, they had the wrong prop (put on by dealer) the whole time and never got the performance they should have.  I would bet that 90% of boat buyers never even look at their prop and have no idea what their boat is capable of doing, they just assume it came from the factory ready to go...and honestly that's a fair assumption.

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I have an 18 MA with a 150 Vmax and run a 19 pitch. Boats should be fairly similar. I roughly cruise at 32 mph at about 3300-3400 rpm and wide open 53mph at 5500.

Reliance is decent all around prop, there is a 19 pitch for sale in the for sale section for 150 shipped. Might be worth a try.

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  • 3 weeks later...

Ok guys got my numbers.. pretty disappointed with them.

Not trimmed; 3000 RMP 21mph / 3500RPM 24mph / 4000RPM 29mph / 4500RPM 32mph / 5000RPM 36mph / 5500RPM 39mph / WOT 5700RPM 41mph.

With trim, numbers almost identical however the lower RPM range had me at 24mph @3000 / 31mph @ 4000 / 34mph @ 4500. From 5000 and ok the numbers didn't increase. I may have seen a 42mph somewhere in it during WOT.

I'm surprised my top end is so slow considering the 150 on board. This was half tank of gas, no fishing gear, me and my 7 year old (maybe 200lbs between us. There is a powerpole, 24v trolling motor also though. 

Are these numbers as odd as I feel like they are?

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MPFit, I have tried the same model hydrofoil that's on your motor a few years back, as a cheap substitute for trim tabs.  The result was more drag and less speed.  There is no substitute for trim tabs.  You already have them so you don't need the foil.  I would ditch the foil and get a 19 pitch prop like Hurricane said.  Also, if that foil is dragging your speed down that much, your motor might need to be raised a notch or two to make sure your cavitation plate is level or slightly above a straight line off the keel - maybe even higher with the pocket-drive cutout on your transom.

Gary

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On 12/2/2016 at 7:22 AM, hurricane said:

I have an 18 MA with a 150 Vmax and run a 19 pitch. Boats should be fairly similar. I roughly cruise at 32 mph at about 3300-3400 rpm and wide open 53mph at 5500.

Reliance is decent all around prop, there is a 19 pitch for sale in the for sale section for 150 shipped. Might be worth a try.

Yank that whale tail off and buy that 19 pitch. See the link.

http://yamaha-motor.com/assets/products/otb/bulletins/bulletin_4stroke_hpv6_rel_hws-redfisher18-f150tlr.pdf

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