Prop Tunnel Hull / Tilt Question

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Callmecaptain
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Prop Tunnel Hull / Tilt Question

Post by Callmecaptain »

I have a 1997 Polar Kraft 1751 MVT Tunnel hull and would like to find out what is recommended in regards to how close or far away the outboard (prop) should be tilted to the boat? I have manual trim btw.

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Callmecaptain
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Prop Tunnel Hull / Tilt Question

Post by Callmecaptain »

No one runs a tunnel jon boat anymore eh? haha

Also curious if any of you have that CMC or Bob's Power power Trim/Tilt jack plate on your tunnel. Do they allow you to trim the outboard closer to the transom than the stock outboard bracket?

surfman
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Prop Tunnel Hull / Tilt Question

Post by surfman »

I don't have a tunnel, wish I did, but I don't think there is a standard setting for any boat. You need to try different settings until you find what works best of your set up. It is all pretty much trial and error since no to boats are alike. I usually try to set mine up with the motor as high and as far back as possible, usually the high and the farther back it is the more efficient it is, of course there is a point at which that is no longer true, you can only find that point by trying different things. Good luck and have fun with it.

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JL8Jeff
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Prop Tunnel Hull / Tilt Question

Post by JL8Jeff »

I have a jet tunnel with a 60/45 jet and I had to put in the transom wedges to get the motor tucked in as far as possible to get rid of porpoising. The boat also porpoised pretty bad with the 40 hp prop motor that was on it when I first got it. I'm thinking the tunnel causes a loss of bouyancy which caused more porpoising, but I'm not sure. I had to adjust the motor height several times and finally settle on the wedges along with some extra weight up front. With a prop motor, you could probably get away with a fin if needed. But you'll probably need to try out several settings to see what works best.
2001 Lowe Roughneck 1652 VT with Merc 60/45 jet 2 stroke

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Callmecaptain
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Prop Tunnel Hull / Tilt Question

Post by Callmecaptain »

thanks for the replies. Jeff, the fin you're referring to, is that a cavitation plate?

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JL8Jeff
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Prop Tunnel Hull / Tilt Question

Post by JL8Jeff »

I think they call them hydrofoil fins or stabilizers. They usually bolt onto the cavitation plate. My old 17' Wahoo center console had a 90 hp Mercury prop motor and I didn't like the fin so I took it off. The boat would porpoise at 2/3 throttle and that was trimmed all the way in. So I put it back on and it was fine. I was going to get one for my 40 hp prop motor but found a Merc jet locally and ended up buying that.

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Last edited by JL8Jeff on 27 Apr 2015, 09:40, edited 1 time in total.
2001 Lowe Roughneck 1652 VT with Merc 60/45 jet 2 stroke

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Zum
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Prop Tunnel Hull / Tilt Question

Post by Zum »

I have a jet tunnel hull...I use a propped outboard, 30hp. No jack plate, I'll I have is a piece of wood to raise the motor as high as possible. It doesn't porpoise with the 30...when I used a 40hp it would a little but only at full throttle...easily fixed with moving some weight forward.
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flatboat
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Prop Tunnel Hull / Tilt Question

Post by flatboat »

a good start would put the prop shaft parallel to the hull surface . . its a real balancing act to get everything right . cav plate even or up a little from the bottom of the transom . the boat will show ya where it wants to run . use a mph app for your phone or gps and watch speed move it one hole at a time till you find the sweet spot when you get close you can go up or down a half a hole by slipping a piece of thick hose over the pin

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JL8Jeff
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Prop Tunnel Hull / Tilt Question

Post by JL8Jeff »

digi wrote:Also curious if any of you have that CMC or Bob's Power power Trim/Tilt jack plate on your tunnel. Do they allow you to trim the outboard closer to the transom than the stock outboard bracket?
I'm not sure about the Bob's power trim, but my Mercury 60/45 jet was manual trim/tilt and I added a Mercury power trim/tilt this winter and it tucks in the same amount. The trim does not go farther in as the bracket is bottomed out just like the manual.
2001 Lowe Roughneck 1652 VT with Merc 60/45 jet 2 stroke

matzilla
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Prop Tunnel Hull / Tilt Question

Post by matzilla »

The CMC will...at least my cmc 130 has 3 degrees negative trim - not sure on the 35

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