Bracket modification

[gofastsandman]

An old truck is in my future. There is no cure for raw adrenaline. You can`t explain why you vibrate for hours after being on stage with a tight smile on your face.

[flyingfrizzle]

Fitting to the boat trying to get the correct height for the 25" Mercury motor:

[Bushwacker]

Friz,

Not sure of the dimensions of your bracket, but your swim platform looks much higher than mine, and the motor mount surface also looks like it's taller than mine so I suspect you could lower the bracket quite a bit from where it is in that last picture, and you'd still be able to raise the motor high enough. The problem with mine is that mount surface isn't high enough to raise the motor any further, and if it was, the lower bolts would want to be right where the swim platform is! On motor height, I have raised my motor one hole or 3/4" above where it is in last picture where it shows the AV plate about 3 1/2" above keel, so it's now at 4 1/4" above keel and the AV plate is still under water, so I think the AV plate wants to be roughly 5" above keel with this bracket with a 30" setback. Sounds like your motor is at least 50 lbs heavier than mine so it might sit a bit lower in the water. (don't forget that the quoted weights are dry weight, so need to add 7.4 lbs/gal for lube oil; don't know it it's true, but I've also heard that some of the quoted 4S motor weights are exactly what you'd read with motor hanging on a scale, i.e., they DON'T include weight of the cowling, so they could be low by another 20 lbs or so!)

Don got the bracket mounting height perfect on mine, with swim platform just an inch or two above the water with a heavy cruising load. Here some pictures and dimensions off mine to give you some ideas. The waterline is right at the top of the green paint, below 3/4" wide gelcoat stripe and 2" wide green bootstripe. When a couple of average size guys (~170 lbs) are on the platform, it's just above the water.

The V at bottom of flotation tub is 4.25" above keel. The swim platform is roughly 16.5" above bottom of tub and about 10" above the chine, as measured along the surface of the transom. For flotation tub comparisons, mine is approximately 32" wide at the tank chines and about 36.5" wide at the top of the tub. Denny

[RUSTYNTABATHA]

would a 20 inch shaft be better on a bracket on these ???? looking at several installations it seems a 20 " motor would make the adjustments easier and not have to redrill holes to raise the motors ???

[beastley]

Originally Posted by RUSTYNTABATHA

would a 20 inch shaft be better on a bracket on these ???? looking at several installations it seems a 20 " motor would make the adjustments easier and not have to redrill holes to raise the motors ???

I second that question. Just about ready to drill holes for my hermco bracket. And I'm concerned about getting the motor high enough.

[Bushwacker]

Originally Posted by beastley

I second that question. Just about ready to drill holes for my hermco bracket. And I'm concerned about getting the motor high enough.

First of all I would mount the bracket on the transom where Don recommends to maximize flotation and because that located the swim platform at the perfect height on my boat. I think optimum motor height depends on bracket setback. Based on my experience, if it's a 30" bracket mounted where Don mounted mine and the motor mount holes are drilled where Don originally put them, a 20" motor would probably work but mount the motor so max possible AV plate height from keel is 5" with ability to lower it if you get too much aeration. I haven't actually been able to mount or run mine at the 5" ht so you're on your own there! Mine works fine where it is; there may be some performance benefits to raising it more, but don't know that for sure or the magnitude of the benefit since I haven't tested that. With a 20" motor, your powerhead will be 5" closer to the water than mine. Not sure I'd be comfortable with that on an offshore boat, although I think the E-TEC cowling is well sealed and baffled. Pretty sure you would need to run a good 4B prop with lots of cup so it bites well when running close to the surface.

If you have a 25" motor, drill the motor mount holes in the bracket as high as possible. To mount it any higher, you'll need a jack plate or a spacer plate about 1" thick extending above bracket with the lower engine mount bolts facing aft with the heads buried flush with front of plate.

[beastley]

Thanks for the advise Denny! Yes mine is the 30" set back also and I marked my mounting wholes according to DON's instructions so my swim platform should be the same as yours. I haven't purchased a motor yet, but I'm at about the same point as Flyingfrizzle on the bracket install.

[RUSTYNTABATHA]

Originally Posted by beastley

Thanks for the advise Denny! Yes mine is the 30" set back also and I marked my mounting wholes according to DON's instructions so my swim platform should be the same as yours. I haven't purchased a motor yet, but I'm at about the same point as Flyingfrizzle on the bracket install.

I'm way behind you guys.. but monitoring closely !!! i may end up with a 20" and a low water pick up on my 20 due to a pumped up merc a friend has to sell me !! but it make my fuel tank WAY too small... but i will get there 4 x's as fast !!!!!!!! LOL still leaning toward a 150 - 175 etec though..

[Bushwacker]

Rusty,

If you're considering a Hermco bracket, you might talk to Don about the possibility of raising the top of the motor mount surface another inch or so, and also putting a bulge in the swim platform just forward on the motor mount surface to prevent interference with the lower motor mount bolts. I think that's what's required to mount a 25" motor with the AV plate 5" above the keel. Denny

[RUSTYNTABATHA]

Originally Posted by Bushwacker

Rusty,

If you're considering a Hermco bracket, you might talk to Don about the possibility of raising the top of the motor mount surface another inch or so, and also putting a bulge in the swim platform just forward on the motor mount surface to prevent interference with the lower motor mount bolts. I think that's what's required to mount a 25" motor with the AV plate 5" above the keel. Denny

definately going hermco if / when i do the bracket ! yalll are going to have to make up my mind !!!! leaning back that way again though.... I would kick myself for doing the transome to 25" and new power and then want the bracket.... gotta make up my mind before i cut / chop / rebuild... lol