best prop for 40 hp

[bigbass55]

i am running a 1992 40 evinrude on a 1993 tracker tournament tx 17 aluminum bass boat. it is rigged on a cmc t/t, with a stingray hydrofoil stabilizer. im turning 4900-5000 rpm's at at 26 mph at w.o.t fully trimmed out with my 11 3/4 by 17 aluminum prop. that is with my normal load of 2 men an all my gear.my motor is about 1/2 - 1 inch above the bottom of boat. i know i need to get my rpm's up and am considering buying a new prop. does anyone have any suggestions as to which aluminum prop would give me my boost in rpms as well as better performance. i am mainly looking for more topend

 

[bigbass55]

Re: best prop for 40 hp

has any1 had success with bombardier props? thanks in advance

 

[Moody Blue]

Re: best prop for 40 hp

No prop expert but I can offer my own experience. I am running a 40HP Mariner on a 14ft whaler style boat and have tried two props. <br />10 1/8" x 15 pitch = 40mph @ 5200rpm good hole shot<br />10 3/8" x 13 pitch = 33mph @ 5600rpm awsome hole shot<br />Rule of thumb is that for each 1" decrease in pitch the RPM will increase by 200. Following this assumption, you would require a 14-15" pitch prop. Keep in mind that your top end will probably suffer a little but the hole shot performance will improve. Only way I can see to increase RPM and gain more top end is to lighten the load in the boat, perhaps raise the motor another inch or two (experimental) or get a bigger motor.

 

[bigbass55]

Re: best prop for 40 hp

rodc, u must have your boat set up right, 40 mph is fast for a 40 hp

 

[Silvertip]

Re: best prop for 40 hp

Changing props is always a trade off as it acts like the transmission in your car. Increased pitch is like a higher gear -- more speed but less power. Decrease pitch is like shifting down -- higher RPM but less speed. I'm very familiar with your setup and recommend you go to a 12-1/4 x15 prop which is pretty standard for this engine. Your RPM will increase and speed will likely stay about the same. To get more speed however, you would need to increase pitch which would lower the RPM even more than current which constitutes lugging which which kills hole shot and eventually will kill the engine. Engine power, gear case ratio, and hull type all dictate how much pitch and engine can handle. Your situation is about 15 pitch (cupped prop).

 

[bigbass55]

Re: best prop for 40 hp

could i gain a few mph by raising the motor a hole or 2 up? i would like 2 gain some extra performance out of my setup, thanks guys

 

[Silvertip]

Re: best prop for 40 hp

Is the antiventilation plate even with or slightly above the keel now? If so, you will not likely gain anything. If its below the keel, yes, some gain may be experienced but it will be due to less drag as the lower unit won't be in the water so far. This may allow pickup of some RPM. Is your current prop cupped?

 

[bigbass55]

Re: best prop for 40 hp

the plate is about 1/2 inch above the bottom of boat. i have no idea if the prop is cupped, i am pretty sure that it is the stock omc prop

 

[Silvertip]

Re: best prop for 40 hp

Cupped props have a lip on the edge that you can see and feel. Uncupped props are smooth all the way to the edge. You can probably raise the engine another hole but in sharp turns you may run into ventilation problems and maybe even loss of water pressure so keep an eye on that. Keep in mind that you are asking alot from a 40HP on a 17 foot boat. I just put a 75 on a 16.5 foot alumacraft after trying all sorts of props and engine height adjustments. Your performance is exactly what I had on my boat. I really think you should leave the engine height were it is and put a 12-1/4 x 15 cupped aluminum prop on it. Your hole shot will be better and because RPM goes up a little your speed will likely be the same or even slightly better and the engine will love you for it.

 

[fishnfiend]

Re: best prop for 40 hp

You can search in the Evinrude/Johnson forum for alot of discussion on propping the 40 hp. Most of the pro's recommend 5800 RPM as a WOT target. At 5000, you might be a little low. I agree with Upinsmoke, a 15 pitch prop is probably about right for your rig.<br /><br />I run an '88 Evinrude 40 hp with a 16 foot Lund aluminimum (has deck, console, livewell, etc). Runs 30 mph at 5500 rpm with a 12x15 prop (got a great deal on a stainless on Iboats - check out their 'prop clearance' deals). Will pull up wakeboarders/slalom skiers although I plan to ventilate to try to get a slightly quicker holeshot. Trolls at 2.4 mph at 750 rpm. This winter, I'll change to 13 pitch to bring the trolling speed down. Have fun.

 

[walleyehed]

Re: best prop for 40 hp

2.4 doesn't sound right...<br />my 200 Rude on my 18ft alum starcraft trolls 2.4-2.6 with a 14-1/2X20 at 550RPM.<br />Could slow your Idle to get the speed ya want....if it doesn't want to run any slower, we can fix that too.

 

[walleyehed]

Re: best prop for 40 hp

2.4 doesn't sound right...<br />my 200 Rude on my 18ft alum starcraft trolls 2.4-2.6 with a 14-1/2X20 at 550RPM.<br />Could slow your Idle to get the speed ya want....if it doesn't want to run any slower, we can fix that too.

 

[fishnfiend]

Re: best prop for 40 hp

Walleyehead - just got my Gps AND tach tried this weekend - trolled for a few seconds - read 2.4. It's possible that I didn't give the GPS time to catch up before we took off again, I suppose.<br /><br />I wouldn't mind idling a bit below 750. This summer, got her running well after sitting for three years and getting the varnish out. Might still have something in the idle circuit - shakes some at idle - didn't want to lower the rpm much below the 750 factory spec, because doubted that it would stay running.<br /><br />I'm amazed that your 200 will idle down to 550 rpm, and troll you at 2.4. Heck, my 40 ought to get down there too, eh?

 

[walleyehed]

Re: best prop for 40 hp

I have some features installed that allow even 500, but that's about it.<br />Sounds like you might need to pull carbs and do a complete cleaning, followed by a linc-N-sync.

 

[fishnfiend]

Re: best prop for 40 hp

Walleyehead, <br /><br />With apologies to Bigbass for hoisting his thread, what features do you have installed that will allow you to idle down so low? Agreed that a complete cleaning is in order. Didn't have the gaskets before, and now I do so just need to do it. thanks for the info.

 

[walleyehed]

Re: best prop for 40 hp

I have Boyesen reeds along with wiseco pistons(Dome shape/piston design), and have fine-tuned the jetting in my Idle circut to allow slower, smoother idle. I have XP heads on this rig and that works agianst me a bit on Idle, but super clean carbs are a must.<br />Yes, we don't want to "Hoist" this thread, but engine performance is translated to on the water performance, and that includes the prop in use.

 

[b.gagnon]

Re: best prop for 40 hp

Your setup sounds right. Check the max rpm of that motor, many motors of that size are 5100rpm max.

 

[bigbass55]

Re: best prop for 40 hp

are you refering to my motor bgagnon?

 

[b.gagnon]

Re: best prop for 40 hp

Yeah! The performance seems to be in the right ball park. The only thing I question is your rpm's. Are you sure your tack is working right? 26-30mph seems to be the average speed for that type of boat with a 40hp. My friend has the same boat with a 70hp and with two people and gear get's 36-39mph, and a max of 42 with one person and no gear(perfect conditions)trimed way out.

 

[bigbass55]

Re: best prop for 40 hp

i am assuming my tach is working right, it is wthe tach that was originaly packaged with the boat, how can i be sure that it is working properly?