I got a free 11ft fiberglass john boat. After about 20mph the front starts to bounce, even in mostly smooth water. Under 15 it doesn’t really bounce. Is this normal for small john boats. It has a patch on a crack it had and it is really lite in the front.
Have you tried adjusting the trim position? Most smaller outboards have 4 or 5 different positions you can experiment with,other than that, you may have to move some of the gear around to get more weight forward.
also, its not uncommon for that to happen if you have a 20" motor on a 15" transom
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IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING
Well the only thing in the front was a cinder block I set in there to help with the weight. The block trick works well in my 10ft twin vee. I think I might have a 20 inch motor so that could be part of it. There is like 3 inches above the entire propeller before the hual. I will have to measure and get a picture of how low it hangs. I used the same 9.9 johnson 2 stroke from my 10ft twin vee on the 11ft john. The motor works fine on the twin vee minus the occasional cavitation when planing off. The twin vee is a mini tank and can handle some decent waves and chop and is sturdy as a floating dock and is way more agile and responsive in turning, a awesome little boat. The john is flimsy in the middle and I’m probably gonna do something to beef it up because of the flex when pounding waves, which I’m not sure if it was always like that or if it was from taking the front deck out or the crack that I fixed. The guy I bought it from said it used to bounce at higher speeds and was bow heavy. I removed at least a hundred pounds of f4not deck and wet foam. The john planes off pretty quick, faster than the twin vee with less bow lift than the twin vee and reaches higher rpms than it too and higher top speed. The john boat hit 24mph easily and i slowed down because of the hull flex and bouncing, it was still climbing so I think it could of hit 27mphish, where as top speed on the twin vee is like 18ish usually but I’ve hit 23mph a few times. I get much better throttle response and pick up on the john boat and it makes my motor sound better to me from first rev to wot. The twin vee sits much deeper in the water though and is like 50 o 100lbs heavier. This is the only experience I have with real little boats and one is a a flat bottom and the other is a cat with deep v’s basically. I’ve never been in a flat bottom john boat before and this was just a test run since I did a quick rough patch job on the floor and bottom. As of now I’m about 20 dollars invested and I liked the throttle response, speed and open spa
From the hull to bottom of my motor is close to 12 inches. My transom is about 16 inches and my motor is 15 I’m pretty sure based on how a quick Google search said to measure it.
Motor looks like it’s hanging too low,might have to build up the transom a wee bit.Order some epoxy resin and fiberglass cloth from clark craft ,it will come in handy with your repairs also.
motor is definitely low on the transom
www.teamcharlestonmarine.com
www.bombislandboats.com
IF I RESPOND IN ALL CAPS, ITS NOT ON PURPOSE, AND I AM NOT YELLING
Describe “hull flex”. How much “hull flex”?
17’ Henry O Hornet w/ Johnson 88 spl
26’ Palmer Scott project hull
14’ Bentz-Craft w/ Yamaha 25
It moves when pounding waves, like half a inch to an inch just the bottom in the middle of the boat. It was kind of sketchy and I have a high tolerance for sketchy stuff. I’m gonna do a giant patch on the bottom to smooth out and reinforce the strips I patched it with and another layer on top to stiffen it up. I did a minor batch job on the crack so I could run it and see if I liked it enough to put some effort and dollars in it. I think I might put something stiff between the inside and next layer of glass. I’m also planning to make a homemade jackplate of sorts.
With that small of a flat bottom boat, I don’t think I’d be trying to get any more speed out of it. My 16’ carolina skiff would do 32mph and that was not very safe unless you had some wide water and plenty of time to react. At that speed your not gonna turn unless you can get the speed and nose down. With yours being a tiller handle and no tilt or trim I’d be leary of trying for more speed.
If you’re going to add a layer of glass on top of the floor, maybe drill a hole and see if the “sandwiched” wood is wet. I bet it is… I had similar issues with my 14’ StumpNockerII. It would flex just like what you have mentioned. No easy fix there but to just prolong the life simply adding the reinforced layer will should get you a few more years out of it!
Fishing Nerd
“skilled labor isn’t cheap, cheap labor isn’t skilled”
There is no wood in the bottom just glass. Its not that I’m trying to get more speed I’m trying to be able to run at like 20ish without it bouncing a ton. It definitely is not a nimble hull but I’ve never need to turn fast any way. I can do donuts like a zero turn motor with my little twin vee and turn on a dime. You got to be careful in it because it can turn so sharp. I’m planning to hit he flats and flood tides mostly and maybe some river fishing in fresh water.