Prop - Questions

[Big dreams]

I am researching props for my 1996 Johnson 130 hp.  I currently have a three blade aluminum that is 14.5 x 23.  The boat flies out of the hole.  The thing is that it stops accelerating at 50 mph.  It gets there extremely fast but then it has a hard time getting over that 50 mark.  I am debating on stainless but I do not want to hit a stump and sheer a pin.  Either way (Stainless or Aluminum), I would like to get a four blade that gets better top end.  I am not sure how fast a 130 would push a 17 foot Champion but I would like to get closer to 60 mph.  I looked up the manufacturers recommended RPM and it says around 5800.
Any ideas?

[LAPORTE]

I have a Johnson Prop out in the barn.  It's aluminum I took it off my 1998 115 johnson Can't remember the pitch or Dia If your intrested shoot me a pm.  Ill ship it to you or bring it to the outdooramma you can give it a try if you like. Also I have a number of a prop guy off BBC his name is Brian.. I can give you the number if you like.

Don

[LGMOUTH]

Couple of things, in general a stainless will go faster than an aluminum prop, A three blade will go faster than a four blade.

What RPMs are you running at top speed with the prop you have now. If you can acheive the 5800 that is recommended easily then you can go up in pitch. Another general rule, lower the pitch the better the hole shot and less topend, higher the pitch less hole shot but better top end. Again this is just a general rule to go by.

I would defenitly try a three blade stainless prop, probably try the same size first and see what the rpms do and go from there.

[Big dreams]

So right now I have a 23p.  If I go higher, lets say to a 25, it will have better top end?  Also, if a three blade goes faster, does the 4 blade get out of the hole better?

[MadWags]

In reality I do not think you will see 60 with that motor. Maybe 53-55 tops with the right prop. Use a 3 blade stainless. If it jumps out of the hole then go up in pitch. It will be slower out of the hole but you will get closer to the top end you desire. Now if you use the boat to pull skiers then stick with what you have. 50 is plenty fast for that boat.

[LGMOUTH]

So right now I have a 23p.  If I go higher, lets say to a 25, it will have better top end?  Also, if a three blade goes faster, does the 4 blade get out of the hole better?

Well there will be a point when you go to high with the pitch and two things will happen, one it will not come out of the hole and two you wont be able to get to that 5800 rpms and the speed wont get there because of it. Another general rule, the lower the pitch the higher the rpms the higher the pitch the lower the rpms. The key is to get the right pitch to run at the 5800 that your motor is recommended. Yes the four blade will get a better hole shot and it will also handle better than the three.

[motocross269]

All good reccommendations..The only thing I would add is to check your prop to transom hieght..If you have an adjustable Jack plate you can play with your numbers there also...

The trick is to get within a few 100 rpms of your max at WOT and still maintain a good hole shot....Remember though everything is give and take...You can't always improve one portion of performance without sacrificing elsewhere....

[Waterfoul]

If you are getting to your 5800 rpm redline I'd say you have a pretty decent prop.  50 mph from a 130 hp outboard is very respectable.  A stainless prop in the same pitch/diameter will likely get you 1-2 more mph maximum but ONLY if it matches what you have exactly... all props vary in pitch, diameter, cup, rake, etc... I've even seen identical props from a manufacturer perform differently on the same boat (my boat!).  One was nearly 1.5 mph faster than the other.  Brand new props right out of the boxes, same exact part number.  Many of the guys I used to race with refer to prop selection as "black magic."  After running more than 20 different props on my boat I have to agree!!

[TheFishinPollock]

I have a 17 foot Champion  with a 140 merc. I runn a 19 right now. Tried a 21 but  the hole shot totaly dissapeared.  I tried a 4 blade and it  just wasn't working so I stick to a 3 blade stainless . Best speed I have got is 63 , but that was empty with 5 gallons of gass.  As the others said. Reaching over 60  just probably won't happen.   Your Rpm's are at the right range at 5800 ish.    When shes loaded with my and porkey in the seat next to me I can just reach the high 50's.      My best opinion would be to go to a stainless and don't hit a stump!

[Lightningboy]

Before anyone can suggest a pitch/prop change, how many RPM at wide open throttle are you getting with that 23?  The suggested max RPM is your target.  Since you say you get out of the hole well, you might try a 25.  The magic formula is to find the biggest pitch prop you can turn and still get out of the water.

SS will get you out of the hole better than aluminum.  The blades flex less.

Three vs. four blades is always a trial & error affair.  A four blade will "grip" the water better, and give the back end more lift.  Some boats need it, others don't.  My TR21 runs faster with a 4 blade trophy than a 3 blade tempest.

The suggestion of a jackplate is a big advantage.  After you've gotten the hull clear of the water, you need to overcome friction with the water to go faster.  That means get more hull out of the water, and reduce the amount of lower unit in the water.  The jackplate will place the motor back several inches, giving the motor more leverage to lift the hull out of the water.  It will also let you raise the motor to any height you need to go faster but keep minimum water pressure.  I wouldn't own a boat without one.

I think you can get to 60, but you'll need more than a prop to get there.  But boy, there's nothin' like the float you feel when you get that hull aired out on a calm morning...

[Big dreams]

Thanks for all of the information.  I purchased the boat last June and being new to the game, I have not thought much about changing the prop until the last tournament when a 21' Champ went buzzing by me going 70+.  Sure he had a 250 on his girl but it made me want more!  Come April I am putting all new electronics and a new trolling motor on it.  When I take it out for the test run, I will be sure to keep an eye on the RPMs. 

[Revtro]

Keep in mind too that water temp does play a small role.  You will notice a difference in cold versus warm water. 

You may not need a 4 blade unless you're in big water.  I assume since you're concerned with stumps, you fish inland.  The 4 blade helps keep you hooked up in rougher water, that's the main advantage I find.  I agree...3 blade stainless for that boat is probably a good bet.  That's where I would start.  If you absolutely end up liking the top end when using a 25p, consider getting one with vent plugs like a trophy so that you can play with the venting for a better hole shot.  You'll be amazed at how much more rpms on the hole shot you can get when you experiment with vent plugs. 

[Bender]

I agree with Tom, I was running a 3 blade and had a little better top speed but it turned like, well a "boat". I went to a 4 blade and it eliminated a lot of the sliding around feeling. There is a lot of playing around to get exactly what you want too between motor height, pitch, etc. I bought a 4 blade that was too steep and had Mark Croxton blueprint and take a pitch out of it: ://www.bassboatcentral.com/marksprops1.htm
I'm sure if you contact him that he would be able to steer you in the right direction as well as helping you dial in a prop to do exactly what you want.

Other than current RPMs the next question will be the prop to pad distance. To measure this I get the trailer on a pretty level surface and then hold a bubble level on the pad of the boat. On mine I put it in the center just under the drain hole. Using the trailer jack I level the boat. Next I set the level on the cavitation plate of the motor and get that as level as possible. Now you can use a tape measure and get the distance between the pad and the ground and then measure the distance between the center of the prop shaft and the ground. Subtract the distance of the prop shaft from the pad distance and you have the prop height.

This setting makes a big difference. Basically you want the motor as high as possible without losing water pressure or blowing out on the hole shot. I raised mine until I saw this and then went back down one notch. Actually I need to do it again since I have added so much weight to the boat in all the tackle that I carry.

[SethV]

Bender has good questions, what RPM are you at right now and GPS speed (not speedo), ect?  Need that detail before we can tell you more. 

You won't get to 60 (unless you are on the trailer), but you might be able to do 50 - 52 mph.

seth

[Big dreams]

Unfortunately I do not have RPM yet.  I didn't think to get it last year being new to the game.  Come April 3rd I will have it though!  I will let you all know then.  Thanks!