dolefin on an outboard
- Thread starter peterbud
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I never had much of problem with squatting, but I did have problems with the outboard on my 222 twisting to the side when hit with a decent wave (even with the screw that prevents the rotation tightened down). I installed the PowerThruster advertized on this site, and it solved that problem. In addition, it protected the rudder from the prop and improved the fuel efficiency. A four stroke 9.9 is quite a bit of weight which is probably causing your squatting problem. Also, as an aside, did you beef up the motor mount including the backing plate or are you using the original motor mount with the wedge? I would be concerned about that if you have not beefed it up. Four stroke motors create quite a bit of torque, and the stock motor mount is not intended for that large a motor, and that much torque.
My 6 hp 4-stroke Tohatsu moved that boat nicely even in big waves and it only weighed about 54 lbs if I recall.
Dave
s/v Lagniappe
O'Day 25
My 6 hp 4-stroke Tohatsu moved that boat nicely even in big waves and it only weighed about 54 lbs if I recall.
Dave
s/v Lagniappe
O'Day 25
A little late to the thread but how much gas do you carry for your outboard and could that be causing the squat? Or is it only while motoring that it squats?
~Craig
~Craig
Hi Peterbud
My boat came with a APS (Yamaha copy) 9.9 fourstroke elect start with remote control on the original bracket. When I used it this summer (late) I found while pushing at 6 knots the motor was way down in the water, I had it adjusted fully forward (bottom of the motor).
The water was up to the lower swivel mounting.
Since then I have purchased a Gairleck mount (the big one with 15 1/2" travel). I am hoping to be able to just raise the motor with out tilting it back.
When the motor was on the original bracket it just crashed down to the lowest level when released and I had to winch it back up, a real pita.
I have removed the angle block from my transom, it was tough but I got it off without damage. I have since modified the new motor mount to eliminate the angle block, this will allow the motor bracket to bolt directly to the transom and keep the motor close to the back of the boat.
I'll post a couple of pic's later.
I would sooner the boat had came with a smaller motor because, with the battery, there is a lot of weight at the back corner.
The motor is 112lbs
Bracket 34lbs (heavy but I have lightened it a bit)
and the group 27 battery ? lbs (heavy)
I am thinking of relocating the battery to the front under the V berth to counteract the motor.
My boat came with a APS (Yamaha copy) 9.9 fourstroke elect start with remote control on the original bracket. When I used it this summer (late) I found while pushing at 6 knots the motor was way down in the water, I had it adjusted fully forward (bottom of the motor).
The water was up to the lower swivel mounting.
Since then I have purchased a Gairleck mount (the big one with 15 1/2" travel). I am hoping to be able to just raise the motor with out tilting it back.
When the motor was on the original bracket it just crashed down to the lowest level when released and I had to winch it back up, a real pita.
I have removed the angle block from my transom, it was tough but I got it off without damage. I have since modified the new motor mount to eliminate the angle block, this will allow the motor bracket to bolt directly to the transom and keep the motor close to the back of the boat.
I'll post a couple of pic's later.
I would sooner the boat had came with a smaller motor because, with the battery, there is a lot of weight at the back corner.
The motor is 112lbs
Bracket 34lbs (heavy but I have lightened it a bit)
and the group 27 battery ? lbs (heavy)
I am thinking of relocating the battery to the front under the V berth to counteract the motor.
I alsopurchased the large garelick bracket and I do raise it up one notch to keep the motor out of the water. I have moved my battery forward which did help some. When you read the info on the dolefin and others like it they say that it helps the power boat to go up on plane. I am trying to see if it would help a sailboat not necessarily go up on plane but help bring the back up some.
My next step is to figure out the best height for the bracket so I don't end up with more holes than necessary. I will probably mount it in the springtime because I will need to FG a new backing board inside for the bolts to go through.
Another project is to make a kitchen unit to house the stove, sink and microwave. The original rolling unit was missing from my boat when I got it.
Another project is to make a kitchen unit to house the stove, sink and microwave. The original rolling unit was missing from my boat when I got it.
Advange of leaving the block in place is that the rudder will not hit the prop. When I did my bracket I went up a size on the bolts.
you might try contacting the manufacturer of dolefin to get their opinion. i have a feeling it won't do much at the relatively low speeds of a displacement hull vs. a planing hull.
also, most of those units require drilling of the cavitation plate and the risk of damaging the lower unit. i am doubtfull the advantage is worth the risk.
can you adjust the angle the lower unit hits the water? in other words, adjust the slant so the prop angles slightly downward in order to get alittle upward push. my power boat's (sorry for the profanity) i/o points slightly downward when in the lowest trim setting.
also, most of those units require drilling of the cavitation plate and the risk of damaging the lower unit. i am doubtfull the advantage is worth the risk.
can you adjust the angle the lower unit hits the water? in other words, adjust the slant so the prop angles slightly downward in order to get alittle upward push. my power boat's (sorry for the profanity) i/o points slightly downward when in the lowest trim setting.
I think the boat is squatting because the engine is pushing the boat at or above hull speed. Nothing will stop this except going slower. Hull speed is (if I remember correctly) 1.34 times the square root of the water line. For a 22' waterline, the hull speed is only 5.8 knots, so if you exceed this, the boat will begin to squat and try to climb its bow wave. Bow up stern goes down. Shifting the weight or adding a Dolefin will not help. This is a fact for all displacement hulls untill you get to planing. Ernie
I talked to the technical people at Davis Instruments yesterday. They said that it will help but not as much as on a powerboat. It still creates some upward force on the cavitation plate.
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