Want some more speed

[Ducker2]

I have a 1990 Evinrude 20hp on a jon boat and I was wondering if there is another size prop I could get to make the boat faster I only use the motor going to and from fishing areas so trolling at low speeds really isnt an issue.

Thanks Ducker2

[Woodsman]

A simple answer - Quite possibly. The best way to find out is to load your boat in a typical fashion you normally would when going to your fishing areas. Operate your boat at Wide Open Throttle & check your motors RPM with a tach. Compare this to your motor's WOT rating. If you are not reaching your listed WOT RPM you have a prop with to much pitch and the motor is bogging down. If you are exceeding your WOT RPM rating you prop has to low of a pitch & could cause motor damage due to over revving. If you are within about 100-150 Rpm (below) of the recommended WOT Rpm you should not expect to improve your speed much without risking damage. If you are exceeding your WOT Rpm a more aggressive prop will help your top end but your hole shot will be slower.

Rick

[mikemicropterus]

Go but the next lower pitch and if it works good if not keep as spare.

Most boats are overpropped and a pitch change can work wonders.

After I put the deck in my 14 fisherman I had to go down 2 inches of pitch to get the RPM back to WOT...

You will need a tach and determine WOT RPM and if that is close to 6000 which is what your motor should turn. Get the rpms as close ofr more than recommende becasue your arm is the limiter if you have a coulpe of 100 more and when you load the boat you will still get your full rpm....and better perfomance.....


The one problem with a jon boat is that they are not really a planing boat, flat bottom so getting a lot out of them is difficult. Also engine height can pick-up the perfomance.. more on that later....


Michael

[Ducker2]

Where could I find the information on a 20hp 1990 evinrude short shaft tiller and where do I get a rpm gauge for an outboard motor. Yes I added a floor and seat and a box on the front and also a bow mount motor which increases the weight substantially.

[mikemicropterus]

BRP website and go to parts store and punch in your model #


20 hp more speed get a 35 hp carb...powerhead for 20 25 30 and 35 are the same... exhaust tube difference and the carb..

More speed.... Boyesen reeds and you get one hell of a smooth idling engine.....my 9.9 has dropped 100 rpm in idle after installing reeds...

To get a tach for your motor you need it to be able to charge a battery and that signal is used to run the tach... I have a meter taht has the tach function built in but that cost me $300 so it is not easy to find an instrument just to measure rpm without spending a few hundred dollars...

A really good engine rebuild could get you 40 usable hp .......

[Ducker2]

When you say engine rebuild how much would that cost? And how much would it be to put a bigger carb on my motor if I decided not to get the engine rebuilt.


Rick