Snake Shooter-engine bracket

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Lane253
Posts: 8
Joined: Fri Jun 22, 2012 5:53 pm
Location: Kent, Washington

Snake Shooter-engine bracket

Postby Lane253 » Thu Sep 12, 2013 12:57 am

Question for Kevin Morin. I read a posted question from way back in 2009 about a young man building a snake shooter that he wanted to add an extended transom engine bracket. I noticed that Kevin told him to make sure to lean the transom an additional 10d. The transom angle for the snake shooter is already 14d. Isn't 24d. a bit excessive? Also, Kevin said that the transom should be lower than 21". How much lower? I would imagine that you all have figured out by this point that I am in the midst of building a snake shooter. I am, and I designed an extended transom where the center most portion of the bracket is hull below, (30" wide). And the outer portions are deck only with knee braces for additional support. It makes the boat have a sloped aft. The best picture of the style is on Bolton Powerboats web site. If anyone cares to look at what I am rambling on about. I am looking for any input that I can get so,fire away. I am using a Miller magic 252 with a 30a spool gun. I am starting to see the logic in purchasing an AC TIG outfit also. This is probably the most rewarding and maddening endeavour an Old Plumber/Fitter could dive into. Thx. Guys,
Lane

Kevin Morin
Posts: 695
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: Snake Shooter-engine bracket

Postby Kevin Morin » Sat Oct 05, 2013 1:16 pm

Lane, sorry not to be by the site for a while and see your questions of me.

power trim tilt outboards have two ranges of hydraulics the lower one being the trim which extends the engine further and further upward and aft. But, in many 10-12 deg transoms this adjustment is essentially wasted since at 1/2 trim up/out/aft there is little or no meaningful thrust. In a 10 degree transom skiff the fully trimmed down engine thrust vector is not enough to pitch the bow down in all cases.

I advocate leaning/raking/building the transom so that the outboard can 'tuck under' farther than 'normal'. My experience and reasoning is; this allows the full 'down/under/trimmed' position of the outboard engine to push the bow down further than the 10-12 degree boats- so, if loaded by the stern you can get the bow down and if not needed you can still use the mid range trim to run the skiff.

The full range of trim is now available for use in pitch/attitude/bow up-down control BEFORE the hydraulics transition to the lift movement range. Unless the transom of a skiff is about 20-25 degrees, the full range of hydraulic trim is rarely usable. The power trim still allows the more leaned aft transom to have the engine fully adjusted, without any loss of performance, so I advocate for the greater angle to the water line to more fully use the outboard's built in features. Hope that addresses the question?

The idea of an ideal 21" transom is from the stern mounted, not bracketed stern and when you begin to fiddle with the lean aft - you place the anti-cav plate farther after the transom or release point of the wake on the planing boat. So.. depending on the hull, and the engine installation- close or far from the bottom's after end.... the engine need to be lifted or lowered to keep the running water line at or near the anti-cav plate. The plate should be about 1/2 to 3/4" below the running waterline so ideally a hydraulic jack plate to lift and lower the engine is best to tune for fuel flow, RPM, speed, load and sea-state.

Without the jack plate, the speed, pitch by the bow and the load coupled with the distance aft the release point of the wake -all these factors will contribute to the running waterline at the engine's leg into the water. So.... what you have to do is draw the skiff, in profile, with the lower leg/gear case and anti-cav plate and then decide how much to adjust for the 'rise of the wake'. I use a rule of thumb of about 1" to 1-1/2" per foot of distance aft the release point. So the ideal of 21" is often adjusted up or down due to speed, load, hull shape and distance aft the bottoms aft most point to the leg 's intersection with the running waterline.

A bracket that is an extension of the planing bottom in the center 30" of your skiff will have a release point at the aft most edge. Depending on your transom rake, and the use or absence of the jack plate (?) and the shaft length (21" or 25" or custom) the transom can be adjusted upward OR downward to suit the rise of the wake as it leaves the boat bottom. The center running surface will tend to have the higher rise per distance than a wider planing surface.

TIG is generally a more controlled welding method which does not required the filler/wire to create the arc therefore it will work much more agilely in the corners and details since the contours of these welds can be followed with our without the addition of weld bead filler material. All full time builders use TIG for the corners and details of their boats.

Cheers,
Kevin Morin
Kevin Morin

Lane253
Posts: 8
Joined: Fri Jun 22, 2012 5:53 pm
Location: Kent, Washington

Re: Snake Shooter-engine bracket

Postby Lane253 » Mon Oct 14, 2013 9:34 am

Kevin, Thanks for the info. I was already planning to tip the transom to 18-19d. I am totally onboard with your diagnosis of trim assemblies. I think 19d. should do the trick. I was just stunned by your answer to the young man that you responded to back in 09'. I now realize that I just misunderstood your answer. I am looking into getting a tig machine or having one of my fitter buddies weld the transom out for me, on this boat anyway.

Kevin Morin
Posts: 695
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: Snake Shooter-engine bracket

Postby Kevin Morin » Mon Oct 14, 2013 9:55 am

Lane253, glad I finally made sense, and its not bad practice to have some help with the welding if your practice time hasn't been as long as it takes to get 'your hand in' as they say.

The bracket, engine mount, gussets and other open access 3" or longer welds in the stern are fine for MIG but often I'll leave the welds one or two puddles short of the wrapped around tie-in to another weld, or the last few puddles of a vertical up or down weld or cross seams.

This is where TIG is the most helpful as you can melt into the beginning or end a MIG weld, then continue filling those last few puddles, turn the ends if needed and tie-I to another weld or make a corner cleaner by using TIG. All these details can be done at a leisurely pace of welding as opposed to having to move around the ends at MIG travel speeds.

Good luck with your build.

Kevin Morin
Kenai, AK
Kevin Morin


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