cant get rpms up

[bigbass55]

hello again guys, thanks for all the previous help you have given me. i have a 92 evinrude 40 on a tracker tx 17 aluminum bass boat. it has a cmc pwr trim, stingray hydrofoil, and new vortex 12 x 15 aluminum prop. my average load is 2-3 men, 12 gallons gas, 1 livewell full and all my fishing gear, sumtimes 1 cooler. all i can get outta her is 26-28 mph at 5000-5200 rpm. its mounted 1 hole from the bottom so i got 2 more holes left to go up. its bout 1 in above bottom of boat. any suggestions on how to get my rpm up and gain sum more speed? thanks in advance

 

[walleyehed]

Re: cant get rpms up

bb55, I had to drop clear down to a 12P to get 6000 (recommended) RPM from my 40 on the same boat. A 13P may work good for you at your elevation, and you can raise the engine until it wants to blow-out easily. If it starts to blow-out trimmed or when turning you're close. You may have to go SS for even better performance if you're wanting that.<br />5000-5200 is a bit low..and hard on that engine.

 

[bigbass55]

Re: cant get rpms up

would a 11 3/4 x 13 rapture ss work well? i just looked and iboats has 1 for around $150. also how would the lower pitch affect my top speed?

 

[Silvertip]

Re: cant get rpms up

Bigbass55 -- email me at DBLSI@charter.net. I have some info for you that I don't wish to share here.

 

[bigbass55]

Re: cant get rpms up

ok thanks

 

[walleyehed]

Re: cant get rpms up

Top speed is only the result of how good we set up the boat...you can only have a certain amount of speed at the right RPM with the perfect set up...we should be concerned about proper RPM first.

 

[bigbass55]

Re: cant get rpms up

would raising the engine 1 more hole and going with a 13 pitch ss prop be a wise thing to do?

 

[walleyehed]

Re: cant get rpms up

Anytime you can raise the engine and lessen drag without serious blow-out or water pressure issues, it's a plus... and yes, if we know the tach is correct, I think a 13 would suit it pretty well.

 

[bigbass55]

Re: cant get rpms up

took the boat out yesterday and took the whole family, with 4 ppl and all gear i could only get 4800--4900 rpm at 23-25 mph, man did my lil 40 struggle. i left the 2 women at the dock and rode a while and got the same 27-28 mph at 5200 rpm. i think i need a really low pitched prop for taking the family

 

[walleyehed]

Re: cant get rpms up

bb55, is that with a 13P??? 4 people is quite a load for that rig...<br />Can, or have you raised the engine any???

 

[bigbass55]

Re: cant get rpms up

the engine is 1 hole from the bottom, there are 2 more holes up. i tried raising it another but it blew out pretty good. those #'s were with my 12 x 15 vortex aluminum prop....any suggestions?

 

[MurdockJr1]

Re: cant get rpms up

I had a 1988 16 ft Lund Rebel with a 1984 40hp Yamaha it had a 11 x 11pitch prop and would do 30mph with 5 people in the boat and turn 5700rpm with just me in the boat it would do 33mph and turn 6000rpm.

 

[bigbass55]

Re: cant get rpms up

i really want to break the 30 mph mark with my average load...it sounds like a reasonable goal to me. does anyone have any prop or setup suggestions?

 

[bigbass55]

Re: cant get rpms up

i had a 17 pitch on originally but couldnt get over 5000 rpm at wot thats why i got the 15 pitch...i dont want to kill the motor thanks for all help

 

[bigbass55]

Re: cant get rpms up

also there is a pretty good amount of spray coming off of the stingray hydrofoil....does this indicate that i should raise 1 more hole up?

 

[bigbass55]

Re: cant get rpms up

bump

 

[walleyehed]

Re: cant get rpms up

also there is a pretty good amount of spray coming off of the stingray hydrofoil....does this indicate that i should raise 1 more hole up?

That right there could be a key element in your quest for speed. If it's in the water while on plane, the engine is likely too low...<br />If the engine is blowing out with 2 holes left, we may need a better prop that will bite at a higher running heigth.<br />Of course we don't want to get high enough to lose any water pressure, but I don't think you're near that point yet.

 

[MurdockJr1]

Re: cant get rpms up

Get rid of that hydrofoil it hurts speed, if you need it to get on a plane quicker buy a set of trim tabs. Did you read my last post that I ran an 11 X 11pitch prop to get were I wanted. A 12 X 15 pitch is too steep for a 40hp engine on that size boat. Just my opinion. Find a marine dealer near you they should let you try different props.