Sea Nymph 14R porpoising

[SeaNymph Man]

I recently upgraded my motor from a 9.5 HP Johnson to an 18 HP Evinrude
Fastwin that has electric start. My problem is that the boat is porpoising at full throttle just after coming up on plane. My starting battery is in the back along with gas tank. I weigh about 210,if that matters any. A fishing buddy
if mine told me this weekend at an outing we were having that I should maybe put a sand bag up front to counter the weight of the battery and gas
tank. I have been told to move the battery forward by one friend,...another tells me to move the gas tank forward. Any other ideas you can think of to stop the bouncing/porpoising at speed. If I would elect to use a sand bag,how
heavy of one would you suggest? Keep in mind I still need to be able to move the boat around on my own when it is not hitched to the car.

 

[~Nickolas~]

Re: Sea Nymph 14R porpoising

I sometimes have this happen to me however I have a 60HP Evinrude with tilt and trim on a 17' TX175 Tournament boat. I just trim out the engine and it pretty much goes away. Having a smaller boat and engine without this feature though you can try and manually adjust the engine on a different angle and it may help. I agree with others about moving weight forward to balance out the boat. I at times add more weight to the front and also fill the front live well tank and it helps. It also depends on the water and if it's calm or choppy. Calm water my boats glides over it and cruises vey nicely around 50MPH but when it's choppy it's a whole nother ball game and it will bounce around and porpoise at times. It also seems if I use a different prop it helps too with the porpoising effect. Anyway just experiment with a few things and i'm sure something will help calm it a bit.

Happy boating,
Nick

Update - One more thing to mention is prop selection. Yesterday I put on a 4 blade Comprop and the boat handled so well I am thinking of making it my main prop. I had smooth and rough water conditions and the boat never porpoised once and stayed on the water and cruised along nicely. The engine ran much smoother and the boat stayed glued to the water and was a much nicer overall cruise on the water. I may keep this as my main prop it ran so smooth and it really did make a difference. Other props I have will get the boat bobbing up and down a lot but this prop calmed it down and kept it down on the water where it belongs. So far the Comprop gets high remarks from me and I like it...