Testing the various hydrofoils - is this too far back?

[tristanlee85]

My 87 Norris Craft 1750 had, when I inherited it, a 2-piece hydrofoil as seen in this picture:



I had a mishap where one of those broke off. And not exactly liking the style of that, I switched it out for an aluminum one from Bob's Machine Shop. Fitment of this one was good, but I feel it was not wide enough, or something. Granted, I changed a lot between the 2 setups: went from the plastic hydrofoil and 5.5" setback to the narrower hydrofoil with an 11" setback. My hole shot was crap, mainly because all the extra weight in the rear from the too large of setback on the jackplate. But this was the setup:



I then exchanged that out for a 7" setback. Hole shot got better, but I had (2) 65lb sand bags tucked in the bow to keep the nose down. Basically, my 27* 3-blade over-hub prop was useless unless I was the only one in the boat. If I planned on a passenger, I had to put my 24* 4-blade thru-hub on to get up on plane. That worked fantastic, except my RPMS were much higher than desired.

So bringing me to now. I have removed my aluminum hydrofoil and picked up a SE Sport 300, which is the widest they had available. Cavitation has never been an issue for me, at least not yet. Both previous hydrofoils were both above the prop. The Sport 300, however, sits back a good ways on my plate. It's as far forward as I can have it.

I have not had this out on the water yet (just installed tonight), but first impressions: does it seem too far back? I won't know until I try. But just curious what others are running. If this doesn't help, I can always go back to the 2-piece.

[Merc 2.5]

I no ur boat ain't super heavy ,but to b runnin a 27 with a 150 on a 17 or 18 ft bass boat just wont work gud imo. I think ur just fighting a prop issue.

[tristanlee85]

It has worked fantastic for a few decades when my dad had it. It's actually a 200. I am the one that screwed up the setup with my modern changes. My additional setback and stern weight from the new jackplate is likely doing more harm than the hydrofoil can help. I hope to test this new one out this weekend.

[staylor]

The SE 300 does look to be too far aft from the photo. Assuming you purchased the SE 300 for 150hp motors and up then the back edge of the foil's locating slot should be up as far forward as possible- until its up against the back face of the exhaust housing. I can't tell exactly where the back of the plate's slot is from the photo. I've run these on a 150 Opti and my current 150 4S with good results- my fishin boat tops out at 64 mph.
Doug

[Merc 2.5]

It has worked fantastic for a few decades when my dad had it. It's actually a 200. I am the one that screwed up the setup with my modern changes. My additional setback and stern weight from the new jackplate is likely doing more harm than the hydrofoil can help. I hope to test this new one out this weekend.

200 gotcha

[tristanlee85]

The SE 300 does look to be too far aft from the photo. Assuming you purchased the SE 300 for 150hp motors and up then the back edge of the foil's locating slot should be up as far forward as possible- until its up against the back face of the exhaust housing. I can't tell exactly where the back of the plate's slot is from the photo. I've run these on a 150 Opti and my current 150 4S with good results- my fishin boat tops out at 64 mph.
Doug

This was the exact one: https://www.cabelas.com/product/SE-S...3.uts?slotId=0

And yeah, it is as far forward as I can get it. In the photo it looks like there is a couple more inches, but that area starts to curve up which wouldn't set the plate flat. I may need to go back to a 2-piece, but we'll see.

On slick water, I think I have topped out around 72mph (GPS) with this setup at 27* prop. Though the foil doesn't do much at those speeds since there's not a whole lot left in the water but the prop.

[KIRCHNER]

you said its a 200? is you lower a 150 gear or 1.87? you cant be turning much top r.p.m. sand bags up front, IMO, you have something out of kilter. you never said whats in the stern. batteries/ wells/ water. anchors? you reduced the set back and it still lousy holeshot? i see your using the lowest mount hole, meaning highest motor setting. thats not too common plus the jplate. thats like total of 8'' up if you go all the way up. can you calc your slip%?

[tristanlee85]

I don't know the specs of the lower. Originally the boat had a 150, which bit the dust back in the 90s. Merc dealer going out of business near the area was selling their motors so my dad put a 200 on it, left the 150 stickers since the vessel is now over powered (175 max).

Stern has 2 batteries, oil tank and light anchor. Original set back (before I messed with it) was ~5.5" on the fixed plate. The I put a 10" plate (with 5/8" spacers for the motor mounts) so I was almost 11" back. Way too much. Exchanged that for a 6" plate, with spaces, so ~7" back now.

That mounting hole was used on my fixed plate which was likely itself lower on the transom. I actually do probably need to go down a hole on the mount, maybe 2, especially since I have the hydraulic lift. I never go all the way up, I can't because it is too high and prop just slips.

I recall doing the prod-to-pad measurement when I set this up, though I can't remember the actual number it was now. I know it was around the suggested drop below the keel. Again, I probably need to lower the motor a hole or 2, and then just jack up the motor to find the sweet spot for hole shot.

[Merc 2.5]

The higher the motor ,the more rpm u will get out of the hole , motor needs a little bit of slip on hole shot to get into it power range to have a good hole shot , kinda like takin off in 2nd gear the way it sits

[tristanlee85]

The higher the motor ,the more rpm u will get out of the hole , motor needs a little bit of slip on hole shot to get into it power range to have a good hole shot , kinda like takin off in 2nd gear the way it sits

I can't go any higher on the mounting holes. Only if I jack it up some for take off. I am usually ~4000rpms coming from the hole. But during that time, it takes a long time to get the bow back down and get up on plane. I think I have good RPMs, it is what they've always been.

[KIRCHNER]

YOU need to go 2 holes lower, maybe 3. you have the plate. with the power head so high, trying to plane is like a person sittin in the splash well.leverage is pulling the nose up. as the bow rises the leverage increases, making things worse. dont exspect an over-hub prop to hook up like a thru hub. that big plate you had weighs a ton, 50+ lbs, i had one.

[tristanlee85]

I moved it up 3 holes so it is now a couple inches lower than before. I still have 1 more hole to go if needed.

[KIRCHNER]

I bet it will be abig improvement, the boat should also turn better. gl

[tristanlee85]

I ended up taking that hydrofoil back. I saw no improvement, and if anything, some degraded performance. I can't tell if dropping the motor as much as I did helped either, at least from the hole shot. When up on plane, I had to jack the motor up about 1.5" otherwise the handling on it is very bad. Just like there is too much motor in the water.

Getting the 2-piece hydrofoil this Friday which is what I originally had. I know that worked well. I may end up taking off the 27p prop and either getting my 25p thru-hub fixed up and cupped or maybe see if I can find a 26p. 27p wiill still be great for say long hauls on the river where the surface is smooth and I can cruise with lower RPMs. Otherwise, on the lakes near me, with as choppy as it is, I can't utilize the benefits of my 27p for low RPMs and high speeds since 50mph is about the max I can go due to the chop.