evinrude 40

[Silvertip]

Re: evinrude 40

When you start experimenting with height adjustments, a water pressure gauge is a highly recommended. These are inexpensive ($40 or so). Since you have some setback it probably won't bother but you are pushing the limits. My thoughts about the 15P prop still stand however. I doubt you will safely pick up 500- 700 RPM by raising the motor -- especially since the AV plate is flush now. Try one hole first and note the result. I'm guessing, but I doubt you'll see much of an increase since this rig is HP-limited. I'd love to be proved wrong!

 

[bigbass55]

Re: evinrude 40

ok guys i raised the engine 2holes 2day. ill get back with how it preforms. now im considering the new prop. im thinking either a hustler 12 1/4 by 15 aluminum cupped for $69.99 or a vortex 12 by 15 aluminum cupped for $64.98. both are here on iboats. does anyone have any reccamendations on which 1 would perform best with my application? thanks guys

 

[bigbass55]

Re: evinrude 40

the hustler is polished aluminum and has vent holes and the vortex is powdercoated. would the polished aluminum be likely to corrode?

 

[Silvertip]

Re: evinrude 40

Don't make both changes (height and prop) at the same time. See how it reacts with the height change only. Then do the prop. Otherwise you won't know which action made the correction and you may spend the prop money for naught.

 

[bigbass55]

Re: evinrude 40

based on what ive been told, the most i could possibly gain from the height change would be 200-300 rpm, thats still 400 - 500 rpm shy of my target. i do see your point tho. ill probably see how it performs based on the height change first and then get the prop if need be. do u have a preference between my prop choices i listed? thanks

 

[Silvertip]

Re: evinrude 40

On that size motor I'd go for the vented prop. Venting allows the engine to rev a little bit more during hole-shot. That momentary slippage goes away at speed. In fresh water, polished or unpolished aluminum should not corrode. Polishing makes it more efficient but again, on that size motor any difference would really be tough to detect.

 

[bigbass55]

Re: evinrude 40

whick of the 2 prop designs would promote best topend speed?

 

[Silvertip]

Re: evinrude 40

I would say Hustler since it is both vented and polished. HOWEVER, My choice is biased toward the venting, not the polish as the polish is only slightly more efficient than the painted Vortex. To confuse things even more, without actually looking at the two props, blade design, rake, and other factors may make one perform better than the other. Boat hull design can affect performance as well. These are unknowns so one must take a chance. Go with what you know. The unknowns can be determined only with experimentation or experience of others running the exact same combination.

 

[bigbass55]

Re: evinrude 40

ok guys i went ahead and purchased the vortex prop. cant wait till it gets here so i can test her out. just for fun does any1 have any guesses on how much ill gain by the new prop and height change? thanks guys

 

[Silvertip]

Re: evinrude 40

I'll stick my neck out: I'll give you 100 RPM on the height change provided it doesn't ventilate, and another 250 RPM for the prop. Why so conservative? Because the boat speeds are not creating as much lower unit drag as they would on a faster boat. Also, you said the 17P was not cupped and the new prop is which negates some of the gain. Cupping accounts for about one inch of pitch. I'll put the RPM at 5400-5500. But unless you test with the same load you had that created the numbers in your first post, all bets are off. Speed is too tough to call since hull design, loading, engine condition and a host of other things are contributing factors. Speed will be no worse than it was (28) and probably better by 2 MPH. Since you've raised the engine, do some base-lines with the 17 pitch prop with just you in the boat. Then test with the 15. Let us know how it turns out.

 

[bigbass55]

Re: evinrude 40

ok guys i got the prop in the mail 2day. looks pretty good to me a few questions: What is the prop nut torque spec? also is there anything i should do when changing the props out? thanks

 

[bigbass55]

Re: evinrude 40

do i need to reuse any old parts as it comes with the xhs hub system?

 

[bigbass55]

Re: evinrude 40

^bump

 

[Silvertip]

Re: evinrude 40

Whatever the instructions say.

 

[bigbass55]

Re: evinrude 40

ok guys we went out to dale hollow lake today and did some fishing so i got to test the boat out. it came out of the hole much faster and the boat seemed faster but cant verify because my spedo. is screwin up. i got her up to around 5200 to 5300 rpm but couldnt trim much because of ventilation. so im gonna lower down 1 hole and see what happens. i think if i lower i can trim more and gain more rpm. thanks.<br /><br />i was able to keep up with my buddy in his 17 ft aluminum procraft with 40 hp mariner maginum today

 

[bigbass55]

Re: evinrude 40

does my thinking sound logical? would i be able to trim more if i lower 1 hole?

 

[bigbass55]

Re: evinrude 40

bump^

 

[bigbass55]

Re: evinrude 40

i took the boat out today after i lowered it 1 hole. i was kinda dissapointed. i could barely turn over 5000 rpm. i could trim more than before and i had little ventilation, and that was in a sharp turn. i got 27 mph on my speedometer but i think its innacurate it felt a little faster than that. so i ask the question. should i raise it back up 1 more hole? i mean it ventilated sum during holeshot and i couldnt trim much but my rpm was higher when it was higher.

 

[Silvertip]

Re: evinrude 40

Are you absolutely sure your tach is correct?

 

[bigbass55]

Re: evinrude 40

i havent had it shop verified. i belive it is the original 1 that came with the boat. could it be possible that the carbs arent fully opening or sumthin? what should i do?