Alright folks, need some help. Just got my boat back from EVT, motor runs great, no hiccups at all, but i believe I have some pre-existing conditions. Here goes... Its long but its needed to get a full understanding.

I have a 23mini lite on a 1542 flat jon. When I first got the motor with 19hours and a brand new 11x10 MB stock prop spinning OOW 4310 and in water 4050-100, I could turn 26mph constantly and hit 27s by myself. With another person I could turn 3950 and 25ish. As seasons and hours go by, my speed got down to 23ish 24ish sometimes lower, lost rpms, umph etc. However at this time, the prop has lost 3/4" and i have some gasket leaks and a head problem. Also, I had a crack in my belt housing that got fixed under warranty. I had to take the lower unit apart, pulleys off etc. So I initiatlly blamed the loss of power on a couple things going on. I was planning on getting some work done by EVT so I was going to wait to size up on the prop.

I just got my motor back from EVT, and it feels/sounds/revs like a pit bull, no problems at all. Before I got it back he test ran it with the old prop with 3/4", 2 people, ran 4500 rpm and stayed 25-26 steady (22-23 before mods on the bad prop). I just thought, oh well thats just the prop, I have a big blade at the house waiting to go on it, that should bump it up a good bit. I get the motor back, slap the blade on and head to the lake. Motor turned blade great, by myself the sweet spot rpm seemed to be around 4400. HOWEVER, this "sweetspot" capped out at 26mph, it held there. Also, my spray didnt seem quite as prevalent as usual. Youd think the blade would sling equal if not more. But it wasnt THAT noticeable, just an observation Something isnt adding up. Im losing speed somewhere. Its almost like what my tach says aint coming out at the prop.

So I start fiddling, listening, tinkering, and theres more noise than should coming out of the belt housing. I cant quite pinpoint which one but it shouldnt be that loud. When I took the bottom shaft out a while back to replace the housing it had grease on the backside of the bearing, like it slung a little out. When there was a crack in the housing, water was constantly in there and it could likely have damaged the bearing. But could it cause this? Do you think the shaft/pulleys could be robbing me? I know its obvious this might be damaged, but how could it possibly cause what Im seeing if it isnt hurting rpms? It dont seem like it would lie unless something was slipping somewhere since my rpms seem ok. I dont have much knowledge of bearings and dont know if one could recieve more rpms than it puts out. I know Ive got more speed, and Im losing it somewhere, just need some suggestions where to look? Thanks alot for the time, I know its alot, but it had to be thorough, let me know what you think.

I would def say you have some stuff worth looking into with your pulley's and gears, but I don't know much about the belt drives. Have to wait on someone else to chime in on that.

My first question would be what kind of condition is your boat in? Hooks, dents, anything? Have you added stuff to the boat since you first got it? Any extra weight that wasn't there when you first started with it? Everything in the same place and balanced? I've picked up 2mph before by sliding a cooler about 6".

X2

Well to start with, the obvious question is, bottom condition on your hull...

Have you noticed any major or minor dings, dents, or imperfections in the hull bottom
especially in the last 5 feet before the transom ???

And then have you considered "shining" up or sanding / polishing that new prop, I have
gotten 2 mph from my sander and 3 grades of sandpaper on the prop face....

Thats the first thing I checked, There is one in the center of the boat but its been there since day one, the rest is just little ripples, nothing major. And nothing has been added to the boat, bout the only thing that changes is the ammount of gas.

Nothing close to the transom? That's where you're gonna lose a lot of speed. When inside the boat looking down at the floor under the motor, there's not any indentations?

If not, I dunno man. Def sounds like you got some issues in the belt housing. May need to play with your gears too with the new power, but it sounds like your rpms are about right.

The biggest thing thats indicating something wrong is I was turnin an 11x10 an 4050 and 26mph, but a 12.25x10 at 4400-50 brings no increase? The physics isnt adding up. Thats why im looking into other things.

For clarification, I got heads/internals, carb, and modified exhaust.

And no, Theres not anything noticeable that wasnt there before : /

Yeah, you got something going on in there with your gears and stuff. Hang around, you'll get some help. Good luck.

I just went and overlooked the hull, Theres one big hook but its been there since I had a longtail on the boat, theres some ripples and little dings, I guess I could take pictures if my standards of how bad hooks are different from yalls. I can get that tomorrow, but this is just me second guessing myself, making alot out of a little i believe.

Bigger isn't always better with props....

There is sum very subtile science in prop design - and - finding "the right prop" for your hull....

Buy a new "original prop" to get a true comparison....

i would check for some belt slip.... but why spin a prop with the same pitch.... pitch is what gives you the push...

11x10 to a 12x10.... I would of gone up in pitch....

check the tac wraps around the plug wire make sure they are tight.... only way to see if the belt is slipping is put it under a load...

Does MB use V-Belts or Cog belts?

Believe its a cog belt. I chewed on the prop thing for a bit and hit a wall. If the old prop (11x10 worn down 3/4") was running 4500, if everything was kosher, shouldnt the blade drop the rpms alot more than just to 4400-50? Seems like somethings missing. Also, If there was a belt slipping or a pulley tension cone slipping between it and the pulley, shouldnt I hear it? This isnt a screaching noise, more of deeper hum. Im going to run both tomorrow and double check, just adding some food for thought.

if its a cog it should not slip.... when cog belts get loose they slap.... basically the loose side of the belt down going gets slack then pops tight.... think of a leather belt popping.... not quite that loud but noticable

a hum could be a lot of things...

I had to take all this apart and redo tension etc etc, so something could be off. The bottom wheel had grease on the back of the wheel, but am I correct in thinking its just a straight shaft? Nothing that could slip on the bottom assembly? I know there could be a problem with the grease, but related to this?

I think I may have to go with Giga on this one. It is is most likely the prop. Brlcla is right about the pitch. You should try one with more pitch and see what happens. You'll definitely see a more noticeable rpm drop but you will gain some speed with some low end drop.

might be yer gps too?sounds like it may have been a bit frisky on the first clocks.seems to happen quite often.my gps must just have arthritis compared to some others.

The speed you say you was running at first is not adding up!!!You need to check your GPS!!!!

I second the GPS. I have the exact same setup as you and get the same speeds by myself. When I add another person my rpm range and speed drop more than you have said. I run my motor on a true mud flat also.

BTW, did you mess with rpm range to see what you ran best at in the first place? Not tryin to be a smarta** but my motor seems to blow the prop out anything over 3970 in water and then I start losing performance. I believe I could run better with my stocker with more pitch than with the original.

It was gps'd on multiple occasions and at rides, next to people, raced multiple times, etc. The gps has been used for years in cars, different boats, etc etc. Also, Ive put enough hours on it, I know my speed, and I know I wasnt going any faster than I was before. When I lost speed from 26-22/23 when prop was bad and had problems, I wasnt just looking at numbers, I felt it big time, I know what 26 feels like and I was going equally as fast before as now. That is not the problem. Got a bud has a 27 on a similar light boat and he runs 25.5-26, I can inch away. GPS is fine.

Do you think the blade would really add zero performance? Im all game for trying it out. Just gotta make sure I can get rid of the other prop, only ran for bout 45min! Is there a good shop I can get a new 11x10 shipped to straight from MB so I can get it done quickly? Just seems that much more prop would at least give me something, but the rpms didnt drop a whole whole lot either which is odd.

Take your worn 11x10 to a prop shop and get a little more cup hammered into it instead of buying a new one... may save you some $$$ and let you test something different....

I think you said you lost .75 out of your original 11x10... so see if a prop shop can make it 10.25x11 or something like that... not sure what the cost these days are on reworking a prop but it has to be cheaper than a new one...

Just got back from the lake and the prop guys might be on to something. I ran the big blade with another person bout 220lbs and held 23mph, by myself could barely hold 26. Slapped the old prop on there and held 27 by myself and held 24 with the friend with more rpms. Keep in mind this is a bad prop with dings, no tip curl, etc. Im going to order a new 11x10 first thing tomorrow and see what happens. Do any of the shops do trials or demos or anything of the sort? This could turn into a bunch of shipping/trading real quick.

it could easily be in your gearing also.... props and gearing go hand and hand...

Im getting into a world I know very little about. Its hard to argue with results, but I dont get why the big blade can perform so well on bigger boats at 4000-100 but it gets beat by a piece of junk on a small boat spinning it 4450? Just sounds fishy, I know very little about this area tho. Just seems odd that if the prop is the sole reason here, how a 11x10 pitched a little more could really outperform it that much. That would be the case if the prop is the sole reason for my speed issues.

pitch and RPM..... and boat size.... what mods were done to your motor?

I can tell you now just by reading that if you are spinning at 12x10 @ 4100 vs 11x10 @ 4500... the 11x10 hands down will outperform....


you are spinning the same pitch at a higher RPM there for faster forward movement... the 12x10 will do better at the low end because it can grab more water to thrust but on the top end it will slow you down if you cannot turn the same RPM as before...

you do the math.... you have 10" of forward movement per rev....

4100RPM x 10 in/rev = 41000 in/min = .647 mi/min = 38.8 mi/hr

in a frictionless world that would be your speed...

now take 4500 and do the same thing = 42.6 mph

also on the top you dont have the whole prop in the water so that is some losses... you have drag... and you have some slip...

Also ya gotta factor in the pulley ratio...

The prop is turning less rpm than the motor....

But otherwise --- X2

And he is likely trimming the 12" prop higher when finding
the "sweet spot" so there is a greater loss of efficiency
with it vs the 11"....

Some very subtle science - in prop design - and matching prop to a particular hull....

I had to buy 5 props from 3 mfgs to finds "the one" on my tunnel hull....

But if our man buys another new 11" just like his original and puts a "polish" on it I'm betting
he will see a big improvement over the 12"....

I agree Giga.... let the motor spin and quit trying to prop it down...

Thanks guys for the help, gonna order an 11x10 first thing in the morning. I imagine Ill run it stock, get a read and see what kind of pitch I need. Who are some guys pretty well-known on here that know there MM props? Dont have any local shops so Ill be shipping regardless.

Now, got some questions on a pitched prop vs the blade. When loaded down, 3-4 folks, what could I see here? Am I correct in thinking the 12.25" would probably get it up quicker/holeshot/etc and the 11x10 would "push" it better with less drop off from small to big load? Havent gotten a chance to really load them, but I did these mods for benefits of pushing a 4th man. Oh yeh, I got heads/internals, carb, and modified exhaust. Didnt get any cams or anythings, just heads and an extra piece or two.

Uh --- 1542 and 4 man load don't go together too well....

You gonna need a bigger hull to haul beef with....

But seriously --- going DOWN on pitch would be more likely
to help you put an extremely heavy load on plane....

Example -- my GDSD 1648 runs fastest when I am solo with
their bigger 2 blade 12x12 prop, but runs fastest loaded down
with 3 bubba sized dudes with their 3 blade 11x11.5 prop...

And unless there was kids or women (lighter) passengers I
would never put 4 in my boat cause it would likely exceed the
safe load limits posted on that lil USCG tag thingy.....

My 4 man load sounds about like your 3 man as far as weight. We do it a good bit, just not with a stock 23hp. Buddy has a 27 on the same hull and can JUST barely plane it out but that "barely" makes a world of difference. Thats all Im looking for, mine falls on its face when you throw a fourth man in, at least it did stock.

Also, whats a good prop shop that knows there MM props to deal with on here? There arent any locals so Ill be shipping it regardless. Gonna need some quick turn-around.

And about the gear ratio, its stock, not sure exactly. Ill have to check.

GPS the same, boat the same, weather similar (humidity and temp will affect motor performance). I would look at your gearing. You added alot of power to the engine and if you stayed with the stock lower gear you are running higher RPM to the point of blowing out the prop. Take your gear down 2 teeth (if its a 50 lower gear, go to a 48) which on a 35 with 38 top an 50 bottom goes from a 1:1.31 gear ratio to a 1:1.26. This will take the RPM down on the motor by adding more load but theoretically keep the prop at the same speed. It can add a lot of performance on a modded motor. THe MB 45 runs a 1:1.26, the 7000 a 1:1.21 or lower. Run the big blade- that other blade has lost alot if its down 3/4"- you loose most of the performance at 1/2", especially hole shot.

As for the grease in your housing- you are either over greasing or have a bad seal. The drive is straight with two bearings in the front and two in the back. There is an exploded view of the outdrive on the MB customer page. When greasing, remove the side allen bolt, pump in grease at the rear zert until the fresh grease comes out the side, leave the allen bolt out and run it at idle in gear for 2 mins until the grease expands and stops coming out the side hole. Then replace the allen bolt.

If you had problem with your bearings you could feel them grating when you turn the prop by hand in nuetral. If you did blow the seal and have water in the housing, its possible but you would feel it - especially if it sat for a while when your motor was in for mods and the bearings got rusted up.

DB,

You know way more than I do bout this stuff --- but he has a 23hp MB
and is trying to put 4 guys on plane --- leastwise thats what I am understanding...

Now GD runs 1.7 to 1 to get their stock 23 GDSD to turn the bigger 11" 3 blade....

What ratio do you think will put his 4 man load on plane with that big ole 12" "Big Blade" ???

I was tryin to lead him back to the original smaller prop to do that, cause
like you said his original is down .50" and holeshot and lo-end power is gone,
even if it will still get up and run hard unloaded at WOT....

12" props are over rated!

Got my new 11x10 in this week and did some side by side comparisons with some ice chests and water. All of these speeds are speeds I could hold for extended periods of time, not over estimating.

BIG BLADE:
1 man: 26 mph at 4300-4350 rpms
Me, 200lbs, 200lbs, and 185lbs: 22 mph tapping 23 once or twice at 4050

New 11x10:
1 man: 26mph at 4300ish
Same 4 man load: 22 at 4000 even

Loads were exactly identical and in the same spots in the boat. Ran them up and down river to get accurate readings. I plained out fine with the load. Started out low and trimmed up and gained rpms until started loosing speed and backed down a hair. They performed almost identical but the big blades holeshot was very noticable over the 11x10. What does this tell ya? Both spinning around same rpms, same speeds, only difference is holeshot. Not sure what direction to head anymore, if adding the pitch to the 11x10 would still be what im looking for or what, let me know what you think about pitch vs. gears here now that ive put them side by side.

The outdrive is getting taken care of, thanks.

what do you need? do you need the hole shot? it is the only benefit... and it tells me exactly what I thought... pitch for pitch they are the same once you are on top...

being that your rpms are the same for both it would play with gearing if you have the time... but what is limiting you at 4300... do you have a rev limiter?

Nope, no rev limiter. Ive got a 4600 in a box that I need to put on. Id trim it up until it lost a mph and back it down a bit and keep it there. The old stock prop was burnin 4500-50 so that sounds about right for the big blade.

Id like to hear more about the gear idea. Theoretically wouldnt speed be the same but lower gear=more low end?

I believe the holeshot would be a big help getting a load up and going in shallow water but my big question is, is an inch in diameter, or inch in pitch better for this? I always hunt 2-4 so Im not too worried bout 1 man speeds but I need to get a load on plane and going.

And thanks a ton for letting me borrow yalls brains for a while, been a big help so far.