1970 flatback

[muscrat]

Hi-

Newbie to the group, I just acquired a 1970 flatback with some issues.  It needs a sole and transom and has some delam at the chines.. I have some stitch and glue building experience but have a few questions about the transom if the group doesn't mind.. The boat currently has a 140 evinrude that runs decent, but of course is a 20 inch. When I do the transom I want to convert it to a 25 inch because I will be using it in the Chesapeake Bay and want the additional height. I do not want to box in the transom or add any motor well, I like the amount of space back there. I would like to fix the transom and continue to run the 20 inch envinrude, and then next spring buy a 25 inch motor.. I understand the jack plate may work, but once I get a new motor I would never need that ability and don't want to waste $1000 or more for 1 year's use. Any suggestions on this? I may also have questions on the chine work when I get to that.. I also realize that this probably means I have some stringer issues as well, so when I do the sole I will fix that to..
Thanks in advance

Steve

[Mad Dog]

Welcome aboard!

My rebuild had a manual jackplate on it to raise the engine (25").  It was basically 4 pieces of 3/8" x 4" x 12" aluminum angle.  Two mounted on the hull two on the engine.  The sides had cut outs to allow for adjustment up & down.  You can probably get some T5052 or T6062 (?) for less than $100 and build your own to allow the drop down.  It will give you about 6" of set back.  You may, however, be limited in how much you can tilt the engine.

[muscrat]

mad dog


Thats what I was wondering, how much setback I would need to be able to still tilt the engine up for trailering and trim.. I guess I will need to go measure. Thanks for the reply!

[Mad Dog]

mad dog


Thats what I was wondering, how much setback I would need to be able to still tilt the engine up for trailering and trim.. I guess I will need to go measure. Thanks for the reply!

I'm not sure what the answer is to that queston.  Try tilting your engine with a board clamped five inches higher and four to six inches in.  Should give you an idea what you need.  Let us know how that works.

[LilRichard]

There are a few concurrent issues you have.  One, I would not go out on a boat with obvious delam around the chines - you are just going to do further damage to the hull, not to mention you run the risk of sinking the hull should the delam turn into a crack.

Second, I have never seen people run a 20" motor on a 25" transom, only the opposite.

My recommendation would be to rebuild the hull correctly (address your delam issues) and put the correct motor on it when you are through.

[Shine]

The motor will not work with a 25" transom, you will only be able to put around at a very slow speed.

Also, without knees or boxes or something else giving stiffness to the rear of the boat, you are going to need to build the transom up much more in terms of thickness.  by raising the engine 5" you are changing how the pushing force of the motor is transfered to the rest of the hull.

[muscrat]

shine,

thanks for the comeback.. BTW I posted on the BBC board about the cap joint recently..  Since I need to do the transom and sole anyway, I am now pretty sure I want to box in the transom like you did on yours. It would give me a place to put a couple batteries or oil tank or whatever. So then would this make sense- fix the sole, build the transom up with additional support like you suggested. If I get a 10" setback plate like fnichols did on his, lower it to the lowest setting, run the 20 motor until I save up for a new motor. Then when I get a new 25" motor, set the jackplate to no vertical adjustment, so that I am using it only for setback only.. Does that make sense?

[Shine]

I remember the post.

The jackplate will probably have enough travel that you can just move the plate up a little when you get a new engine - fill the old holes

Be aware that you may need to move some other weight forward to account for moving the engine weight back.  On my flat back, i moved the fuel tank and console up.  Remember when you move you console up, you actually move the console plus 350-500 pounds of people forward (if you have two guys standing behind the console while running)

[muscrat]

shine


Thanks again..  I am going to start cutting everything out next week so hopefully will be able to show some progress  :)

Steve