1992 evinrude 40 hp wot rpm too low

[bigbass55]

ive got a 1992 evinrude 40 hp outboard rigged on a 1993 tracker tournament tx 17. It has a cmc power tilt/trim and an aluminum 11 3/4 by 17 prop (stock i think). i also have a stingray hydrofoil stabilizer on it. im turning around 5000 rpm at 26 mph or so w/ 2 men an all my gear.<br />i was told that i need around 5500 rpm. any help would be appreciated. can i gain speed and better performance with a new prop?

 

[bigbass55]

Re: 1992 evinrude 40 hp wot rpm too low

is 5000 rpm at wot acceptable? or am i lugging the motor and slowly killing it?

 

[ob15]

Re: 1992 evinrude 40 hp wot rpm too low

A couple of questions.<br /><br />Where is the AV plate in relation to the bottom of the boat & can you trim the motor out all the way? Usually the AV plate can be a lttle above the bottom. Also, with the CMC T&T the offset will allow you raise the motor higher.

 

[bigbass55]

Re: 1992 evinrude 40 hp wot rpm too low

the av plate is level with the bottom of the boat. 5000 rpm's are with the motor fully trimmed out

 

[bigbass55]

Re: 1992 evinrude 40 hp wot rpm too low

the motor is mounted in the lowest possible position. would i lose water pressure if i moved up a hole or 2? maybe a 12 3/4 by 15 prop would solve this issue?

 

[ob15]

Re: 1992 evinrude 40 hp wot rpm too low

What is the setback for the CMC unit 6"? That would allow you to raise the motor at least 1 hole. I would try 2 holes and see how the motor runs. You are still low enough not to worry about losing water pressure. The plan is to raise the motor until the prop starts to ventilate when trimmed at most efficient setting. Then lower motor one hole. Every boat is different. Just to let you know, I have an 89 Johnson 50 on a 15' skiff. The motor is mount 1 1/2" above the keel (with no setback). If it was setback like yours, I would raise it 1 more hole.<br /><br />To add to this, with a SS prop, the motor can be raised higher as they bite a lot better.<br /><br />How does the boat plane now? What kind of hull is the Tracker?

 

[bigbass55]

Re: 1992 evinrude 40 hp wot rpm too low

the boat is 17 ft. aluminum. it planes out pretty well, unless you have more than 2 people on board

 

[ob15]

Re: 1992 evinrude 40 hp wot rpm too low

I would try raising the motor at least 2 holes & see how it runs. If ok, try 3. It's pretty easy to raise. Do a search & you should find lots of posts & methods. <br /><br />Good luck & let us know how things turn out. You may still need to get another prop, but at least the setup will be tweaked real good and the boat should perform like it never has before.

 

[bigbass55]

Re: 1992 evinrude 40 hp wot rpm too low

do you think i would gain much topend by raising the engin?

 

[ob15]

Re: 1992 evinrude 40 hp wot rpm too low

Most defintely. If you raise rpm with the same prop, top end speed will increase. Should be able to get an extra couple out of it by tweaking the setup.

 

[Mark42]

Re: 1992 evinrude 40 hp wot rpm too low

The OMC manual for my 93 lists the proper WOT operating rpm range as 4500 - 5500. My setup has the motor right at 5000 at wot. I suggest you find out what OMC said the wot rpm range is before making changes to the setup. <br /><br />When I had a smaller prop the motor reved higher up to 5800 rpm and it did not sound happy. It had a really buzzy sound. At 5000 it humms along nicely.

 

[bigbass55]

Re: 1992 evinrude 40 hp wot rpm too low

i do not have the manual. does anyone know the correct rpm range at wot for this motor? it sounds fine at 5000 rpm

 

[Silvertip]

Re: 1992 evinrude 40 hp wot rpm too low

That motor will be much happier at 5500 RPM. My ten year old 40 Evinrude routinely ran between 5500 5800 RPM and when traded had compression readings of 146 and 143. Try a 15 pitch prop on it. A local dealer will have a bunch of them laying around he'd very likely let you try if you left him a deposit.

 

[bigbass55]

Re: 1992 evinrude 40 hp wot rpm too low

does anyone have any suggestions as to which brand or style of prop i should choose if raising it doesnt cut it? im thinking maybe a 12 by 15 prop? probably aluminum

 

[Silvertip]

Re: 1992 evinrude 40 hp wot rpm too low

Your motor is rated at 4500 - 5500 rpm. If you are interested, I have a vented 12-1/4 x 15 cupped aluminum, a 13 pitch cupped aluminum and a brand new (used once) Stainless Steel 13 pitch cupped that will fit your engine.

 

[fishnfiend]

Re: 1992 evinrude 40 hp wot rpm too low

I have almost the same setup, but an '88 40 hp, 16 foot aluminum bassboat. I can't remember, but I may have a different gear ratio in lower unit than you. If you search "40 prop" in the Johnson/Evinrude forum, you'll find several more discussions on propping the 40.<br /><br />Short story: I have a 13, 15 and 17 pitch prop. I HAD a stingray also, but ditched it because it's so dang thick I was getting a rooster tail (before I raised my motor).<br /><br />I read that your hydrofoil should ride nearly out of the water at WOT, if not you are getting alot of drag - especially with the Stingray. Unfortunately, with my boat, when I raise the motor that much, the prop breaks out on turns, and I have to throttle back until the prop catches again.<br /><br />I settled on a ss 15 for all-around use with my rig. This winter for trolling, I'll go down to the 13. The 15 is best for combined hole shot/top speed for my rig (we've been skiing and wakeboarding alot recently also). The motor is mounted 2nd hole from the top (cavitation plate slightly above bottom of boat).<br /><br />It costs nothing to raise the motor (put a chunk of wood under the skeg, loosen the bolts, and raise/lower the front of trailer with the jack). I'd mess with that first before spending the $$$ on a new prop (unless you find a smoking deal on an SS on Iboats like I did )<br /><br />That's a great motor. Have fun!!

 

[bigbass55]

Re: 1992 evinrude 40 hp wot rpm too low

thank u guys, i think i'll try raising my outboard first before spendin $ on a new prop

 

[ob15]

Re: 1992 evinrude 40 hp wot rpm too low

Most defintiely raise the motor. SS props are always good props to use. You can usually tweak the setup more with SS vs. Aluminum. I would still shoot for 5800 rpm.<br /><br />Good luck & let us know how things work out.