prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

[craze1cars]

Just picked up a new-to-me Landau 170 Bass boat (it's kinda like a Bass Tracker or Alumacraft Mod-V, all welded aluminum, rated to 75hp). It has a 2000 Johnson 50 hp, which my my understanding has a 2.42 ratio and an operating range of 4,500 to 5,500. Current prop is unknown aluminum (I believe factory original), 12 1/4 x 15 pitch. It's a little bit chewed up, but not bad. I'm gonna buy a prop and relegate this one to spare duty.

I just got back from a top speed run with my typical load, perfectly trimmed I got exactly 5,500 rpm at 24 mph (boat speedo...forgot my GPS). Based on slip calculator I used, that works out to 26% slip. Ungood. Seems slower than I expected it to be.

Obviously I want to improve this. Stainless is my most likely choice, but I'm open to another aluminum if someone has a suggestion. But which style/brand, and what pitch? I'd like to target a slightly lower rpm, just so I'm not flirting with the max all the time...maybe 5250-ish in a perfect world? I'm thinking about trying a 16 or 17 in a stainless. Not sure the motor will push it well enough...maybe it will.

What say you?

Does anyone got a good educated guess/suggestion for what I should buy and/or try???

Thankyaberrymuch!!!

 

[craze1cars]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

Some more info that might help, courtesy of iBoats:
Boat: 2000 Landau Boats Pro 17 Bass All-Weld

They say this is a 620 pound boat. My power trim motor is 190 lbs according to manual. My performance above was with about 450 lbs of humans/dog/anchors/small cooler/fishing gear, plus the usual bow mount trolling motor, 2 batteries, 10 gallons of gas, and probably 10 gallons of livewell water.

Holeshot is excellent. Top speed is what it is. I'll have to pay more attention to my motor placement, but I do not believe I can raise it, because I can only run the power trim button up for about 1 second before it starts to lose bite with the water and sucks air/slows down a little (it does not have a trim gauge, I just trim it out by feel till it loses bite, then notch it down till it bites again...this results in my max speed). Even with trim full down it looses a bit of bite in sharp turns, but then grabs it right away when I straighten out. I have to assume raising the motor would make this worse. But maybe a different prop would allow it?? But overall I'm happy with current performance in terms of holeshot and turning bite. It only slips a little when I go real sharp which is rare. It never blows completely out of the water or anything like that.

I guess my more general question is, what should be my realistic expectation of top speed for this rig, and how can/should I get there in terms of prop selection. Thanks again!

 

[steelespike]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

I figure your at about 1600 lbs. I wonder if your ventilation may be prop related more than motor height.
Can't really tell much about your actual slip without your gps speed Your speed at 12% slip would be about 28.
A 17" prop at 5100 rpm 12% slip would be about 30.
It does appear you could go to the 17 if your willing to give up some hole shot.
It's pretty obvious that with the 15 you would over rev with a light load.

 

[craze1cars]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

Actually considering a Turning Point Hustler. Good reviews, inexpensive. Plus I owned run on an underpowered 3.0L runabout before and it worked beautifully. I am concerned with the following added efficiencies, that this motor won't have the juice to push a 17:

1. No more nicks in the prop. Should reduce slip.
2. More cupping/design of Hustler prop. Should reduce slip.
3. 2" added pitch. Should reduce RPM.
4. I do intend to add a 3rd battery and bump up to a 24v trolling motor very soon. That's a little more weight.

And I don't fish alone much, so rarely will my load be any less than what I tested with.

Would 1 to 4 above create too much extra bite to allow my motor to turn a 17" pitch in the motor's mid RPM range? Or should I go ahead and try it...I would kinda hate to go to this prop only to find my rpms tank all the way to 4500 or something cuz the motor can't get into its powerband...wondering if it might be smarter to just get the Turning point in a 15 pitch...

BUT if your prediction of a 17 gets me about 5100 at about 30, I'd be tickled pink. That would be fabulous. Holeshot is not that important to me, since I'm never towing skiiers or anything, so this boat has some holeshot to give up in my opinion if I can turn it into a little better top speed. Fish around here are fast...I'm having a hard time catching them at 24 mph, but surely I could catch more fish at closer to 30 mph...LOL...

Also, do you believe the Hustler in general will perform well with my setup, or do you/others have any other brands/styles to suggest? Thanks much for your reply!

 

[Sea Rider]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

You're underpowered with a 50 being that boat rated for a 75. How's your actual hole shot with current prop and load ? Fast, slow ? Being your wot range very tight just 5000-5500, going one pitch up should achieve 5300-5350 rpm at wot, going 2 up should reduce rpm to 5100-5200. Those numbers are relative as you will need to test both pitches under waster trail. Find a good prop Samaritan that can lend you a 17 to test, probably ideal one for your set up.

Happy Boating

 

[steelespike]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

While not ideal a 50 is 2/3 of the rating.I believe they suggest 2/3 to 3/4 minimum.
If your hole shot is excellent I would think a 17" would be adequate.
The Hustler is an aggressive prop but I believe it is vented which helps hole shot.
You better check into that.

 

[Sea Rider]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

When rigging a boat with under powered engine, what's stated as to take into account is 70/75% of it's max rated HP to achieve acceptable performance. But would be advisable and helthier to engine to reduce overall weight, passengers in 25-30% to have better overall end performance.

Happy Boating

 

[craze1cars]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

Sea Rider, thanks for your input, but I just bought a $3,000 boat. New motors are $6K and up...also I answered your first holeshot question in my follow-up post...so I have to assume you didn't fully read or understand my entire situation, nor my current performance and desires.

For now I'm looking to spend $200 or less on a prop to get the most out of what it has. I'll probably fish from this boat less than 10 days a year. With that usage, the motor will last me until 2040, even if it's loaded hard. In the meantime it just needs to get me there the best it can, nothing more.

I'm quite aware that more HP will make it faster, but I have no interest in the high cost of re-powering...unless you can suggest a $200 repowering alternative...

And as I stated earlier, my holeshot is downright excellent. It spins right up real quick, minimal bow rise, gets on plane in about 2.5 seconds maybe? I frankly don't find it underpowered at all for my tastes, and for the load I'll run with it.

26% slip calculation seems to me my biggest problem, not lack of HP, and that's all I'm really trying to improve right now. If I can find a little more speed in the process, that's more important in my book than holeshot as long as it doesn't struggle to get outta the hole with too much extra prop bite.

I might roll the dice and try the 17" Hustler. Since both of you think it might work OK. Worst case I can sell the housing on Ebay at a small loss and buy a 15" later if the motor can't push it.

I'll try to remember to report back after my attempt! And Steelspike, thank you also very much for your valuable input.

 

[steelespike]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

Looking forward to your results. I feel sure the Hustler will improve your slip and may even allow you to raise the motor a little more
for even less drag.

 

[craze1cars]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

The Hustler is an aggressive prop but I believe it is vented which helps hole shot.
You better check into that.

Just got my Hustler in the mail. Website clearly promotes the benefits of the vent holes you mentioned. I was disappointed to find my new Hustler prop does NOT have any vent holes.

I've sent an email to manufacturer and am awaiting response. Seems to me that either they forgot to install them in my prop, or they are falsely advertising non-existent features on their website...

I owned a Hustler years ago on a runabout. It did have vent holes. Maybe they're getting away from them now?

Haven't run the prop yet. I'll update when I do. Also will update regarding the missing vent hole issue if/when they respond to my email.

 

[craze1cars]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

Got a quick email response from Turning Point. Thought I'd share:

"We do not vent the small props. We start venting props from the LE1/LE2 1317 size in both aluminum and stainless steel , up to our large size V6 and I/O props. We have found thru our test program that venting the smaller propellers gives no noticeable increase in performance. If you are dissatisfied with our product, simply return it for a refund thru the dealer you purchased it from. Thank you for pointing this out, we are currently changing our web-site to correct this."

It's nice to know the company is responsive, and they are acknowledging and presumably correcting their website marketing error.

I'll report back again with performance results of this prop after I find time for a test drive.

 

[craze1cars]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

RESULTS. Slight improvement in terms of speed, bite, along with a reduction in RPM...which is all good. But my slip calculates now to be identical. Hmmm. Might be a situation of garbage-in, garbage-out, as I still used the boat speedo and the boat tach...maybe one or the other or both are wrong.

Anyway, here's where I'm at now...

Old chewed up 15" pitch prop: 5500 rpm, 24 mph = 26% slip
New Hustler 17" prop: 5300 rpm, 26 mph = 26% slip

This prop doesn't lose bite at all in ANY turns. Holeshot suffered just a little but is more than adequate for my tastes...probably still less than 4 seconds to plane, so no problem there, especially considering the more heavy load this time. So anyway I've confirmed my motor can easily turn a 17" prop with a heavy load, but I'm making assumptions that my tach and speedo are accurate...and I realize this may be a big assumption.

The other wild card here is that my load was different, HEAVIER this time in the worst possible place, as I added a 15 hp kicker motor hanging out the back (temporarily...for test-drive purposes only today, I'll clamp it on occasionally for a HP restricted lake I'll sometimes fish, but normally it won't be onboard), plus my fishing mate today was probably 30 lbs heavier than the last one. The kicker was fully tilted out of the water, so no drag, just weight.

So my next plan, since it bit in turns so well, is to go ahead and try to raise the motor an extra hole and see what happens, and make a point of going back to a more "normal" weight load & distribution, and bring a shop tach and a GPS to confirm or dispute some figures.

Long way of saying I've made some progress in the right direction, but learned very little.

And we nearly got skunked this morning. Only 3 bluegill, while striving for Bass...so this new prop clearly has not improved my fishing one bit, which is a setback...

 

[steelespike]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

26% slip is like a pontoon setup only probably worse than a a properly setup pontoon.
You need to beg borrow or buy a gps. At least with the accurate speed we may be able to see if it makes sense
and get an idea if the tach is right.

 

[craze1cars]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

Couple minor tweaks. Couple questions answered also...

Went out with my 'typical' load today. Had a GPS. Motor was also raised a hole. Also confirmed turning motor over by hand that my ratio is indeed a 2.42.

Results:

27.8 mph gps (this corresponds to about 25 on my boat speedo, same as before)
5400 rpm (I have still not verified my tach accuracy, but it seems to work smoothly and consistently)
17 pitch hustler prop

This gives me actual slip results of 23%. Better than earlier presumed 26, but far from good.

I also had an opportunity to stick my head out the back end while my buddy drove at speed, and I cannot see my A/V plate...it's still a little bit under the water. Turning performance was fine and prop was biting well.

So next plan is to raise the motor another hole before next fishing trip and re-test. Probably aughtta confirm my tach also, but I'm prioritizing fishing with my buddy rather than wasting both our times chasing a few mph...

Another small clue. While I was running top speed my buddy was moving around the boat messing with his fishing gear. When he moved forward just a few feet, the boat slowed down 1-2 mph. When he moved backward, boat sped up about 1 mph. This was regardless of me trying to compensate with trim. And my previous test-run with a full 80 pound kicker motor hanging on the transom gave me the SAME speedo results as today. All this weight distribution tells me that my boat seems happiest with more weight back and less forward...it must be plowing a bit and not lifting the bow high enough to get it on "the pad"...not that I expect a 50 hp to have enough grunt to really lift the bow...but it does help me with future weight distributions, and tells me that when I add my 3rd battery for 24 volt trolling motor, sticking it in the back of the boat with the other two will not be detrimental to performance...I might also get my anchors and tool box out of the bow storage compartment and move them somewhere aft also.

Of course moving the motor up another hole may change some of that.

All very interesting stuff...plenty of things to play with in an attempt to make incremental progress.

And AGAIN, skunked on fishing this morning. So I need to work on something there also....

 

[steelespike]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

I would suspect the tach until we prove it is right.
If we take your numbers and insert 12% slip we get 4900 rpm not an unreasonable number.
I think its safe to say weight would have a rearward bias.But too much will kill your hole shot
and may make it pound on the swells.
Moving stuff from the bow to the midsection may work better than all the way to the stern.
If you have a battery just to start the motor a good garden tractor battery will do that fine.
You may get to a point where just a few pounds might get it up that last little bit.
2 batteries is almost like a additional person.

 

[craze1cars]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

EUREKA! Here I thought my tach was all nice and accurate because it worked smoothly. It is NOT accurate.

I have an infrared tach...the kind where you shine a light at a reflector on the flywheel. While I can't do this at speed, I was playing with it running on muffs in the driveway today.

For a short 5 seconds or so I would rev the motor to 3,000 rpm on the boat tach. The inductive tach was reading about 2450. Then for a brief burst I set the boat tach on 4000. The digital tach said about 3,250.

Going fishing tomorrow, and motor is again raised another hole.

Now I'm off to do some quick Johnson research and see if maybe my Teleflex tach is simply set on the wrong setting and simply needs a screwdriver put to the selector on the back. Does anyone here know offhand which "pulse" setting I should be using with this year 2000 2 cylinder, 2 stroke Johnson 50?

 

[craze1cars]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

Ok...tach now verified/corrected...motor raised ANOTHER hole...new gps results...

29 mph, 5200 rpm, 17 pitch prop, 2.42 ratio = 16% slip.

Hmmm...not ideal, but a heckuva lot better than I thought I had. And I'm still very comfortable with my 17 pitch prop.

Another thing I noticed regarding weight distribution...Every time I moved my 200 pound body 3 feet back in order to peer over the rear of the boat and look at the A/V plate, the boat would actually gain about 0.8 mph. When I came back to the center seats it slowed back down to the original speed. And this is AFTER I had already moved 2 anchors and toolbox from bow storage to far stern storage and filled my rear live-well to the brim. So this boat seems to REALLY like having MORE weight in the back...and it likes it as far back as possible. So this makes me feel very comfortable stuffing a 3rd battery back there for the 24V trolling motor upgrade plan...

As for motor height, I STILL cannot quite see my A/V plate on the surface...it's obscured by spray for sure. But I'm concerned about going up another hole because I already have lost a certain degree of bite in the turns by raising 2 holes so far. I'm forced to trim down for any type of turning, which is OK...it still bites, but if I try to turn while going 25 mph or more the prop loses bite real quick.

For my next test I think I'll fill my fuel tank to the brim (also in the rear) and toss an extra car battery that I have laying around in the rear compartment to help simulate my future 24V setup, AND I'll go ahead and raise the motor up to the last hole and see if the prop can still bite or not with the tail end crammed down further in the water as this boat seems to prefer.

This stuff is kinda fun to chase. Every time I make a change I gain just a tiny little bit...and now that I have good data to work with I can actually see what is happening. Surely I can squeek a legitimate 30 mph outta this thing with a little more finessing...cuz everyone knows you can't catch fish if your boat is slower than 30...

 

[craze1cars]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

Motor raised to very top hole now, and I can FINALLY see the A/V plate while in the upper range of speed. Water still peeing strong outta the pee hole so no problems there. I gained a little touch of speed and a little efficiency:

17 pitch prop, 2.42 pitch, 5250 rpm, 30.1 mph = 14% slip. Wasn't glass either...light chop. Might get a hair more in perfect conditions.

AND I caught some decent fish today! NOW that my boat goes 30 mph, it catches fish! I knew it would work! Mission accomplished.

I think that's all this 50 hp rig is ever gonna muster, so I'm just gonna call this prop good enough for now...

 

[Silvertip]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

Motor raised to very top hole now, and I can FINALLY see the A/V plate while in the upper range of speed. Water still peeing strong outta the pee hole so no problems there. I gained a little touch of speed and a little efficiency:

17 pitch prop, 2.42 pitch, 5250 rpm, 30.1 mph = 14% slip. Wasn't glass either...light chop. Might get a hair more in perfect conditions.

AND I caught some decent fish today! NOW that my boat goes 30 mph, it catches fish! I knew it would work! Mission accomplished.

I think that's all this 50 hp rig is ever gonna muster, so I'm just gonna call this prop good enough for now...

Now you should put the original 12-1/4 x 15 back on (damaged or not). Test exactly the same and I'd bet the slip number comes down some more. That prop has been tested against everything from a 13P stainless to 17P cupped & uncupped and I always went back to it. On my 16 footer the tach shows 5800 which is perfect for that motor and hole shot is excellent.

 

[craze1cars]

Re: prop advice please, 50hp Johnson 2 stroke on a 17' aluminum bass boat

Now you should put the original 12-1/4 x 15 back on (damaged or not). Test exactly the same and I'd bet the slip number comes down some more. That prop has been tested against everything from a 13P stainless to 17P cupped & uncupped and I always went back to it. On my 16 footer the tach shows 5800 which is perfect for that motor and hole shot is excellent.

Interesting thought which never occurred to me I guess...I might do that sometime and see what happens, certainly nothing to lose.

I'm curious why you feel 5800 would be perfect for this motor? Johnson says operating range is 4500 to 5500.