evinrude 40

[bigbass55]

hey guys. ive got a 1993 tracker tx 17 aluminum bass rig with a 1992 evinrude 40 hp on it. right now it has a sting ray hydrofoil on it and its rigged on a cmc power tilt and trim. heres my question. its currently mounted on the lowest of 4 holes and it dead even with the bottom of the boat. the cmc has 6 inches of setback. i turn 5100 rpm at 26 mph with 3 men loaded down and about 28 with 2 men. how much performance could i gain by raising the motor a couple of holes on the transom? by the way the prop is a 11 3/4 by 17 stock i think. thanks in advance

 

[gatorred]

Re: evinrude 40

keep cavation plate it even unless you got ss prop or it will mess up blow out is what it will do but ss prop try moving up a hole at time 1/2 in at time only use stainless steel prop well moving up

 

[bigbass55]

Re: evinrude 40

somewhere i read that for every 5 inches of setback you can raise the engine 1 inch am i correct?

 

[javsam]

Re: evinrude 40

the cmc installation manual states you can have cavitation plate 1 to 3 inches above bottom of transom. as the water under the boat flows past the transom it actually rises up allowing you to run at higher heights,which results in less drag.<br />some people have experienced an increase of 100 rpm per hole, but this depends on your hull so its a try and see method.<br />javsam

 

[WillyBWright]

Re: evinrude 40

One thing that doesn't help is that as the tilt bracket tilts, it also lifts the motor much more than if it was a conventional trim&tilt outboard on a rigid bracket. Dittos on the stainless prop. But try raising it up a hole at a time and see where it runs best. You can hang the motor and unbolt it. Use the trailer to raise and lower the back of the boat by lowering and raising the tongue.

 

[bigbass55]

Re: evinrude 40

my hull is an aluminum modv design. does any1 have a similar set up?

 

[Silvertip]

Re: evinrude 40

You have way too much prop for the boat and load. I went through the same process you are with a 17 footer running a 40 Evinrude and it turned out a 12-1/4 x 15 prop was the best overall. At 5100 RPM you'll kill that engine. It wants to rev 5500 - 6000. I've run 11-3/4 x 17 uncupped, 12-1/4 x 15 cupped (both aluminum) and a 12-1/4 - 13 cupped stainless (once). The 15 is simply the best. In fact I sold the motor, kept the 15 and 13SS. If you are interested in either, post an email address and I'll get back to you.

 

[bigbass55]

Re: evinrude 40

would my topend stay about the same with the 12 1/4 by 15? is my current prop cupped or uncupped im pretty sure its stock?

 

[Silvertip]

Re: evinrude 40

It's probably cupped but the 17 I had was not. There is no such thing as a stock prop. Engines about 40HP and up do not come with props because the manufacturer doesn't know what type of boat the engine will be installed on. The selling dealer normally recommends what prop works best on a given boat. Since you are lugging the engine now, going to less pitch may increase speed since the engine can rev a little more free and get into its power band. It will definitely give you better hole shot.

 

[walleyehed]

Re: evinrude 40

You got some good advice here...I would recommend raising the engine 1 hole and test-it may vent some when trimmed, but if it doesn't vent coming out of the hole, raise it 1 more and test.<br />The more set-back you have the less trim you need for max speed.

 

[bigbass55]

Re: evinrude 40

thanks for the help guys. i have a few more questions. i have learned that the max recamended rpm for my motor is 5500, but its ok to go over that? also how many rpm would i gain by raising the motor? last question, what reasonably priced prop would you suggest for my application that would produce the best top end speed? thanks

 

[bigbass55]

Re: evinrude 40

ok guys i just remembered sumthing, if you trim the motor a lot it starts to porpoise, would this indicate that the engine is to low?

 

[Dhadley]

Re: evinrude 40

Dont worry about the rpm. Those guys love it. It'll live a lot longer propped at 5800 than it will at 5500. Try to get to 5800-6000 without decreasing pitch.

 

[bigbass55]

Re: evinrude 40

mr dhadley, thanks for your help in this matter, what do u think about my porpoising issue?

 

[Silvertip]

Re: evinrude 40

I am constantly surprised by the results some people experience by making various changes in setup so by all means try raising the engine. That said, 17 foot boat + three gents + gear + 40HP does not make for a speedy rig with a 17 pitch prop. Been there & done that. The prop calculator I use shows 32 MPH @ 5800 with a 15 pitch using a 10% slip figure. Using a 17 pitch at the speeds you posted showed 26% slip. At least try a 15P. I think your engine and you will both be happier. Your local Evinrude/Johnson dealer probably has a pile of them laying around and would let you try one.

 

[Silvertip]

Re: evinrude 40

I am constantly surprised by the results some people experience by making various changes in setup so by all means try raising the engine. That said, 17 foot boat + three gents + gear + 40HP does not make for a speedy rig with a 17 pitch prop. Been there & done that. The prop calculator I use shows 32 MPH @ 5800 with a 15 pitch using a 10% slip figure. Using a 17 pitch at the speeds you posted showed 26% slip. At least try a 15P. I think your engine and you will both be happier. Your local Evinrude/Johnson dealer probably has a pile of them laying around and would let you try one.

 

[Silvertip]

Re: evinrude 40

There you have it -- two identical posts = second opinion.

 

[WillyBWright]

Re: evinrude 40

Porpoising's cheapest cure is to shift the load towards the bow. That don't cost nuthin. Trim tabs, work very nicely as well. Prices vary depending how fnacy a system you want. Just don't get those spring-loaded things or the plastic ones with a curve that flexes. They should be rigid and adjustable. Wander on over here...<br /> http://www.iboats.com/mall/index.cg...=trim+tab&submit.x=0&submit.y=0&submit=Search

 

[bigbass55]

Re: evinrude 40

based upon your experience, how many rpms do u think ill gain by raising the engine,say, 2 holes up on the transom?

 

[bigbass55]

Re: evinrude 40

at 2 more holes up do u think losing water pressure will become a concern?