Tiny boat performance help

[Texasmark]

Well I had a 10' Lowe (brand) Lake John for a lotta years. Gave it to the crew (as a thank you as they needed one)nm that built my shop when I moved out of town to the country....Muskogee, Ok. folks and great workers....... The Lake John was wider and had deeper sides than normal Johns of 10'. I built a rack over my P/U at the time and I could go to the water, working alone, slide the boat off, launch it, install the engine and gear and be on my way.......I had a ton....a ton of fun with that boat.

After a rain, when fresh water was leaking into the local lakes, I'd get up before the crack of dawn, get ready, go out and work my trot-lines for Channel or Blue cats, and then come home shower and go to my professional job....afternoons were just the opposite... Then on weekend nights when the new water was coming into the lake, I would go to the tributaries after work, working trotline for cats, or with a bucket full of minnows have a blast with Crappie (white Perch). I had a 1975 era new Merc. 7 1/2 on it and it planed out like a champ and ran like it meant it. Zero problems with any of the things discussed here.
Geez what a wonderful time of life to have a good paying job, have great health, have lots of water nearby, and the facilities to enjoy that......geez, I really miss my earlier life............

 

[kalebsheridan]

View attachment PXL_20260402_015243380~2.mp4

 

[kalebsheridan]

I have an 8-foot pram with a 7.5 HP outboard . . . similar situation with planing.

Weight shift will help, but you may want to make some static trim tabs out of marine HDPE board (starboard) and stick them on the transom.

I was curious about that. How would I design such a thing? Would bending some aluminum plate work?

 

[kalebsheridan]

And what motor HP wise , was hanging on the back ?

5

 

[kalebsheridan]

What do you mean "transom has some negative angle"? If the top of the transom tilts back slightly, that's normal. That tilt would be beneficial to any tilt pin adjustment. If it's toward the boat, most unusual, then you will certainly need to move the tilt pin farther out.....maybe all the way to get the thrust angle to bring the bow up.

Yeah the top of the transom sticks out farther than the bottom. I'll keep playing with trim and see what I can manage.

 

[tpenfield]

I was curious about that. How would I design such a thing? Would bending some aluminum plate work?

Here you go . . .


.
One on each side of the transom, . . . Done.

 

[kalebsheridan]

Here you go . . .

View attachment 415478
.
One on each side of the transom, . . . Done.

Awesome I may have to make some! Would they run so they are flat with the hull of the boat? Or should they have some angle to them?

 

[redneck joe]

Ted will answer better than me but if you go more than hull it will a.ways nose you down so if once on plane you don't need nose dow then stick with same as hull. That essentially gives you a longer boat.

 

[tpenfield]

Even or only a slight downward angle would be all that I would do . . . Too much angle will tend to slow the boat down more than desired

 

[kalebsheridan]

Update after lots of farting around. Adding weight forward helps a lot, but I recently made a no-drill compression plate for my 5 hp. Boat has much better hole shot, and I don't need to shift my weight much to get out of the hole. Needs a little adjustment still, I had to raise my motor 2 inches. I can send a photo of the plate if anyone is curious.

 

[redneck joe]

pictures are required. You musta missed the fine print in the rules....

 

[kalebsheridan]

Here's a test fit after modifying it. I'll probably trim back the edges and vertical fins a bit for less drag. I think the downward fins are only necessary to add rigidity to the glass and funnel water around the prop.

 

[kalebsheridan]

 

[Mc Tool]

Looks similar to my "Permatrim ", NZ made out of 5mm aluminium plate .
There are some here who them but Im liking mine , I have had one on all my boats . They def give you a bit of lift and generally the motor answers to trim adjustments better .
As you can see the peeps who make them dont have near as much forward of the prop as you do . I think by law of the lever the closer to the transom the less effect it has ....but hey ...give it a whirl

 

[Texasmark]

Looks similar to my "Permatrim ", NZ made out of 5mm aluminium plate .
There are some here who them but Im liking mine , I have had one on all my boats . They def give you a bit of lift and generally the motor answers to trim adjustments better .
As you can see the peeps who make them dont have near as much forward of the prop as you do . I think by law of the lever the closer to the transom the less effect it has ....but hey ...give it a whirl View attachment 419032

It's a "Moment of Inertia" thing......Foot-Pounds. You have the pounds in the items lifting capabilities which is constant but when you add "feet" to the equation it becomes more effective! Its like sliding a pipe over the handle of a wrench trying to turn a nut that won't budge!

 

[IslandExplorer]

Nice homemade hydrofoil! I bet if you trim it down a little in front as previously discussed you will gain that extra speed from a little less drag and it'll be perfect. Just needs cool paint job now.
Those things have an added benefit of protecting the spinning prop from bumping into dock pilings and things as easy too. My 14 foot tinny with a 9.9 was wayy nicer handling with one. Made all the difference in my opinion. The negligible top speed loss was a happy trade for all the handling and planing improvement.

 

[kalebsheridan]

Looks similar to my "Permatrim ", NZ made out of 5mm aluminium plate .
There are some here who them but Im liking mine , I have had one on all my boats . They def give you a bit of lift and generally the motor answers to trim adjustments better .
As you can see the peeps who make them dont have near as much forward of the prop as you do . I think by law of the lever the closer to the transom the less effect it has ....but hey ...give it a whirl View attachment 419032

That is very similar. Yeah I do have quite a bit of mine close to the transom. I left a lot of glass so I could trim it back later if I needed to. Easier to remove fiberglass than to add it back. I might trim it back a bit, but I've also seen other plates with almost as much plate forward of the prop as behind. Those may be for tunnel hulls though. Like I said, I'm gonna play with it more. It splashes pretty bad currently, so I need to play with the shape, but also raise the motor another inch or so.

 

[kalebsheridan]

Nice homemade hydrofoil! I bet if you trim it down a little in front as previously discussed you will gain that extra speed from a little less drag and it'll be perfect. Just needs cool paint job now.
Those things have an added benefit of protecting the spinning prop from bumping into dock pilings and things as easy too. My 14 foot tinny with a 9.9 was wayy nicer handling with one. Made all the difference in my opinion. The negligible top speed loss was a happy trade for all the handling and planing improvement.

Thanks! I'll very likely trim the front back so long as it doesn't affect the structural integrity. I forgot to mention, it's a two piece design molded to the motor foot, so I don't have to drill any holes in my ventilation plate. I'll take pics of that later. I'll definitely trim some of it off, but I wanted to see what I could get away with before I started removing glass. Needs more work too, flattening, filling, then paint of course!

 

[IslandExplorer]

The no drill feature is really nice and prob rare for those. The one I have requires 4 holes through cavitation plate. Theyre typically made where one size kinda-fits most, and a lot not well.

Personally I hardly hesitate to drill holes in everything I own but most def prefer not to. = Might be a marketable design once you perfect it.

 

[kalebsheridan]

Thanks! I just really didn't want to drill any holes if I wasn't confident it would work. I've seen a few no drill versions but they are both expensive, and not made for small outboards.