Theretics of my new prop

[dazk14]

We have set up that EXACT rig numerous times, and 85's hundreds of times as we were an Evinrude dealership and there was also a Galaxy dealer ~70 miles away.

The OP is clueless, which is why this forum exists with countless VERY GENEROUS and experienced members donating their time and incredible knowledge.

The OP is also behaving like an insulting @ss with his comments to Frank A. that has over 7,000 posts and the OP's apology was a joke.

I won't shed a tear when he grenades that motor and learns the hard way the term, "A Debt of Gratitude".

I'll pass on this one.

[Philster]

Olivian11, I don't know who you think you are, but if you are going to argue, read what you are arguing with first. Your response to me, in which you quoted me, clearly reflects you didn't read my post.

First, more HP adds more speed to most boats even if the prop ain't changed because rare is the day that a given setup runs spot on to redline. On your little wagon, the prop isn't tuned to hit the exact redline of the engine. Props are compromises. Chances are, it's falling short. Add HP and she'll run closer to redline and bingo: More speed.

Second: A 4-blade prop has more surface are to hook up and getting out of the hole is better/faster, but it comes at the expense of top speed.

There is so much wrong with your understanding of speed and RPM, the only way you have a chance is to come back humble. While you're mulling over cars versus boats, just realize that props are like the rear gearing in a car. If you want more speed, you need to run a taller final drive ratio. To do so, be it in a boat or car, you have to come back with more power.

To spin a 25p prop and run 75-80, you'd have to get things a spinnin', and you'll be needing more power.... just to magnify the 'just spin it faster' thing rattlin' 'round inside your head.

If only it were that easy. Physics doesn't play nice. Sorry. It's not linear.

[Silvertip]

Im fully aware what horse power is but the same reason my ford ranger can out pull full size pickups when im running 340hp vs their 410hp because of my gearing, or the same reason a civic with 200hp can out run a car with 320hp, they are geared to do so, raw hp at the crank is not the same as hp at the wheels, the same way with a boat, after the ratio takes place in the unit that effects how fast it spins.
hp in a car is bennificial when your talking about accelleration, more torque is a benifit when your towing more... HP is not everything. The same reason a mac truck can pull 80,000lbs wether it has 650hp vs 800hp because the trany is geared for the diofference to compensate with torque.

As a performance car enthusiast (aka racer) those vehicles have several advantages that a boat power plant does not. Your "racer" has a multi-speed transmission whereas a boat does not. It has one gear so in effect the boat is starting out in high gear all the time. it must launch you, cruise at a reasonable rpm and the engine must be able to reach the manufacturers recommended WOT rpm. If it can't, you have too much prop. If it over revs, you have too little pitch. That prop, whether it is a two, three, four or five, blace, steel or aluminum will provide whatever speed that prop and engine combination is capable of. Increasing pitch beyond that WOT rpm is of no benefit because the engine simply can't twist it. While "race" engines can turn very high rpm, in a boat they will be dead before you pull away from the dock due to water injestion due to valve overlap. Radical cams cannot be used in a recreational boat for that reason. Put your 15,000 rpm powered bike in high gear and try to move off the spot. That sir, is comparing a car/bike to a boat. And the crack about a diesel being the best boat engine -- it is. they can turn monster props at relatively low rpm. They do it in ships all the time. About 450 - 600 rpm wide open, pushing a gazillion tons of scrap metal and 5000 people. at 30 MPH.

[Philster]

The OP is negligent in forgetting about power-to-weight ratios; further, when they want to make a case about gear reduction and the wonders of it, they neglect to mention that top speed plummets with gear reduction.

With boats, the top speed is often flirted with; on cars it rarely matters. Hopping up a car can be just dropping to a short gear (higher numerically) or adding HP or both, because cars are all about acceleration. Sure, give me 50HP and let me switch out to a shorter gear.

A 35 MPH boat will run at 30-35 A LOT. If you jack up a boat to get a screamin' hole shot and she runs at 25-27 instead, that's a bigazz difference. And cruising RPMs? Jeesh.

(Cars/trucks can have gear reduction beyond stock, but boats are already running at max gear reduction or darn close to it. We can talk about custom labbed props, which is like gear reduction down to increments not available 'off the shelf'. Sort of like having 4.11's and actually getting the whole rear rebuilt to magical 4.13's. Imagine that! On a boat, with the prop, you can do that with a prop shop).

[sublauxation]

im not saying your wrong, but my origional post i also asked for a spiffic prop, then was told that my cousins boat does not proform the way i satated, you have no idea what my motor is capable of, for all purposes the 85hp motor currently has 120 raw hp at the crank... i was asking for aid in locating something im having a hard time locating as well as some other advise, i dont need to be told im wrong when ive seen other thing in action

This is kinda fun Actually, and you guys can correct me if I'm wrong, older outboards were rated at the powerhead whereas newer motors are rated at the prop. That would imply that your 85 (or your cousins) is actually less than 85 at the prop shaft, or less than, for instance, the 90 ETECs mentioned several times for comparison. Now if your motor is really a 120 then let us know as that will surely change the advice given to you. I think SS is right with the 15P recommendation. This is not a urinating contest, turning a bigger prop does not a bigger man make There is no shame in a 15 pitch prop though admittedly the big gnarly ones with high rake look cool, especially in stainless.

On that note I highly recommend having a custom prop shaft made so you can put a big prop on that thing. Please report back to us your results so we can pass them along.

Seriously, These people know what they are talking about. They are trying to help. It would be good to listen to them.

[Philster]

Let the OP keep mulling over this and I think it'll 'click':

Prop too small = better hole shot and lower top speed with chance engine can run way past redline
Prop too big = terrible hole shot and top speed probably falls short because engine is lugged and cannot reach redline

Prop too small is actually a better condition for the engine provided the engine has a manual rev limiter called an informed operator, or an automatic electronic rev limiter.

Prop too big is bad all around. The engine is being lugged, placing internal stresses on it that -- depending on a variety of factors, such as engine design -- might result in serious internal engine damage or advanced wear/stress.

Keep thinking of the prop as the rear gearing or final gearing that affects final drive ratio. On a boat, unlike a car hot-rodded to provide acceleration, well, a boat will run at/near its top speed so often that you generally don't want to play with the final gearing so much so that you knock off too much top speed.

Drop to shorter gears on a car and you bask in the wonders of gear reduction, and you get better accel numbers, which is what is desired in most cases that I can cite. Drop to shorter gear on a boat (smaller prop) and you can get better acceleration (potential is there) but...but...but -----> read this next part alert ----->but.... a boat will typically operate up near its top speed a lot... and sometimes will run at its top speed most of the time, especially the little 2-strokers. Most people are not interested in taking a 35 MPH boat and turning it into a 30 MPH boat that will blow redline, nor should they want a 35 MPH boat that is overpropped and lugging, fails to reach redline and is experiencing loads (via lugging) that it might not be able to handle.

To turn taller gears (bigger props), you need more power.

[aerobat]

what a fantastic thread !

1: If the speed in wich the prop turns and the pitch determins the speed in wich the boat travels, why do people boast a higher HP motor when they are just adding weight?

correct !!! because of that i plan to scrap my heavy 150hp V6 evinrude and put the much lighter 5hp kicker yamaha on the transom and plug in the 14.5 x 20p stainless from the rude. as a further benefit the yamaha revs higher than the evinrude and since speed is just prop pitch x revolutions because the prop spins "free" in the water i should go ballistic !

cheers !

[Philster]

Just gear it so it spins a whole bunch and you'll leave them 300 HP stroker* motors in your wake!



*Even the stroker motors that are actually oversquare, but billed as being strokers.

[olivialyn11]

got the motor dynoed, i have 123HP
found this prop that aperently they have no reason to produse,
http://www.savvyboater.com/rubex-hr4...21-rbx106.aspx

is their still any objections or better advice then my motor is worthless?

[steelespike]

What rpm is the 123hp developed at? I believe the 85 uses a 2.29 ratio, and 115-130 and more use a 2.00.

[olivialyn11]

What rpm is the 123hp developed at? I believe the 85 uses a 2.29 ratio, and 115-130 and more use a 2.00.

5K. Motor is rated 4500 to 5500. As we went closer to 5500 saw numbers closer to 130

[smitty477]

Interesting post - we are on the second page and I think this is where we are at:
- No baseline data avaiable on props or rpm's
- No comparable weight on this combination
- An unknown lower unit ratio
- An 85 hp outboard that is perhaps actually 123hp (45% up)

And the questions are revolving around picking the correct prop for this application.

[1080tommy1]

For someone that just got into outboards this is an interesting discussion. Threads like this while on the surface could seem negative actually have great explanations of how to prop a certain setup and the reasons why. I think that the first post the OP is stating that he would like to keep speed but adding a four blade prop will reduce top end speed and give a better hole shot. I also in all of my reading understand that a motor which is smaller such as an 85 hp would be more appropriate for a three blade prop because of hull design and horse power. I am not trying to add negativity to this post and create a pissing contest but rather attempting to understand prop selection because I am still trying to dial mine in. Just seems like all I have read also states that if you are going to add a four blad prop, pitch should be decreased and I am assuming this is to account for the drag and pitch of the extra blade reducing rpms. Seems to me 15 to 17 pitch would be right in the ball park at least for starting out and attaining a baseline from which to really dial in the right prop.

I have to say you may want to listen to these guys because everything I have been advised has worked out pretty well from this site and I was starting much the way you are because my motor was severely underpropped and the prop was dinged up pretty bad so it really was of no use in development of what prop I would finally wind up with.

I hope you do find the right prop and get her going well but I have to say reading all that I have in the past month or so on props, a 23 four blade would probably have your motor lugging pretty good and I think being underpropped is better than overpropped becuase if you are underpropped, at least you can use that particular prop. Overpropping is a no go because anything over no wake will result in stress on the motor.

[Captain Shikaboo]

lincolnpopcorn.gif

[olivialyn11]

I i would like to jump on this, i dont care how many posts you have, it just shows that you spend time in front of a computer instead of a boat, Also i Like that you have data and speffic memory of a boat and motor that today are 40+ years old. And the motors not stock, if i tear it apart, will throw new sleaves or a power head on it and destroy it again.

We have set up that EXACT rig numerous times, and 85's hundreds of times as we were an Evinrude dealership and there was also a Galaxy dealer ~70 miles away.

The OP is also behaving like an insulting @ss with his comments to Frank A. that has over 7,000 posts and the OP's apology was a joke.

I won't shed a tear when he grenades that motor and learns the hard way the term, "A Debt of Gratitude".

I'll pass on this one.

This is quite funny

Interesting post - we are on the second page and I think this is where we are at:
- No baseline data avaiable on props or rpm's
- No comparable weight on this combination
- An unknown lower unit ratio
- An 85 hp outboard that is perhaps actually 123hp (45% up)

And the questions are revolving around picking the correct prop for this application.

I origionaly stated that it was a 85 motor, never stated it was a stock unit, when i tried to relay any data i had which was my cousins boat, i was told that i was wrong, and aperently me having a boat is just like owning a car, i can throw some biggger tires on and make my car go super fast.

We are working or motors to get the most out of a powerhead, weve modofied intakes, heads and are going to start on lower units soon, I also previosuly stated on page 1 that the unit had 120 hp, if i was going to spend 2k buying every different prop for my boat i would have never asked for advice the nearest place for me to get parts for my boat is 45minuts in one direction and the lake is and hour in the other. so borrowing every prop is not an option. and aperently props im looking for shouldnt exist because they would have no use but ive found them after all my uncle-in-laws who spend just about every day on the water cant be wrong either, he had a 19' with a real 85hp with a 17" pitch and it ran 35mph at 5200rpm, if i had the same stock motor i would have just boght a 17" blade and ran it circles.... but this is not a stock motor,

The lower unit is off of a 1977 150hp
Uper unit is a heavly modified 1975 85hp prodicing around 120-130hp

[Philster]

Ok, So im new to the boat world, got a 19' galaxy bowrider and a 1975 evinrude 85hp 13tooth spline

Ive been looking into the origional prop that came on the motor and it seams that it was a 13-3/4x23 and a 13-3/4x21

Ive spent about 6 months rebuilding the entire boat, new floor, transom, seats, dash, paint, and now the motor. Ive been reading about props and motors and unlike a car, the RPMs of the boat are what determine the speed, so my two questions?

1: If the speed in wich the prop turns and the pitch determins the speed in wich the boat travels, why do people boast a higher HP motor when they are just adding weight?

.

Quoted for a reminder of how this train wreck got started. You asked questions that were answered; refused to accept the answers, and are insulted we don't value your complete lack of boating experience in countering anything you offer out of your own lack of knowledge.

[steelespike]

Your 150 leg is likely a 1.85 ratio.Your power head is as much as 130 hp.
I looked up 9 new 150s on boats ranging from 17ft to 22ft.mostly glass one aluminum average prop size was 17" with largest 19 smallest 16.
Speeds 39-48 mph rpm 5200 to5750. One vary fast =Checkmate 20 ft 1400 lbs had a 22" prop did 61 at 5500.
Take what you want from this but it doesn't appear a 23" will work.
Was your Galaxy originally an I/O? couldn't find a outboard.

[sublauxation]

The cool thing about interchangeable hubs is that while you may waste $276.95 on a prop, that $40 hub can be used with any other Rubex prop.

[olivialyn11]

Your 150 leg is likely a 1.85 ratio.Your power head is as much as 130 hp.
I looked up 9 new 150s on boats ranging from 17ft to 22ft.mostly glass one aluminum average prop size was 17" with largest 19 smallest 16.
Speeds 39-48 mph rpm 5200 to5750. One vary fast =Checkmate 20 ft 1400 lbs had a 22" prop did 61 at 5500.
Take what you want from this but it doesn't appear a 23" will work.
Was your Galaxy originally an I/O? couldn't find a outboard.

I couldnt find any other out boards either, when i bought the boat it was outboard.... i would have preferd inboard because its much eaiser to modify a regular engine block then a o/b motor. i only weight 1800lbs do you think if i could squeez a little more out of the motor a 19"4Blade would be to much, or just run a standerd 19? as long as i stay above 4500 the motor should hold out right? as long as we didnt mess up any machineing? its all balanced so im not really worried about a top rpm

[steelespike]

I really think your better off with a 17" pitch.Keep in mind all the tests were 150 hp motors and the boat with a 19" prop was 1650
lbs and had a fast bottom ran at 48 mph @ 5450 fastest of the non Checkmate types.
To fully realize your hp you need to be able to reach close to your 5500 you had in your Dyno test.
I have a feeling your bottom is probably like a deep V.It will give a nice ride but not too fast.
If you do the 19 you might get into the low end of your range but will likely be sluggish. And won't have much reserve for loads or water sports.If you go with a 17 and it ends up a little light you can still use it and just watch the rpm.
If the 19 is over propped the motor will lugg and you shouldn't run it for extended time over a fast no wake speed.
You certainly could test it and use it while trying to fine tune the setup but over time lugging can cause premature motor problems.

[sublauxation]

If you are anywhere near Minneapolis or Fox Valley WI I'd be more than happy to let you test with my 3 blade 17 pitch TP Hustler. Are there any prop shops nearby that will let you try them? Some are decent about it as long as you put the money down first. I know for fact there are a lot of decent 13 spline Evinrude props out there on EBAY in both 17 and 19 pitch. (I just put 13 in the search area and that weeds out most of what wont work) The 4 blades are harder to find. I bought a nice SS 15 pitch last spring for $50. Definitely stick with the interchangeable hub if possible if you go new.

[aerobat]

The lower unit is off of a 1977 150hp
Uper unit is a heavly modified 1975 85hp prodicing around 120-130hp

gents, dont you get it that he is most probably joking us ? you make here a brain storming for something that is nonexistent.

please show us some pics of your heavily modified 85hp pushing now nearly 130hp . what did you installed ? a supercharger?

[Philster]

I would like to see pics of how the engine (prop shaft and antiventilation AV plate) sit in relation to the bottom of the boat.

Putting the prop into dirty water by burying it even 1-3" will knock off some RPM.

Having it too high on a V bottom boat will kill bow lift. W/out bow lift, there is more wetted hull, which = drag.

Boats without a real serious V can simply err on the high side. The prop doesn't need to be low enough to produce bow lift. V-bottom boats don't have this luxury. They have a sweet spot, usually only 1 to 1.5" in height along a given range. For example: On a given V bottom boat, the prop shaft sitting 2" below the bottom might be perfect, whereas 3" below knocks off RPM/speed.

Given all the variables, I think this one needs to be cleared.

EDIT: at the end of the day, only running the boat on plane and looking at the lower unit to see where the AV plate sits in relation to the water matters. It should skim just at the surface (visible), w/ maybe a little splash going over it while under way at speed.

Also, since the OP seems to have speed tricks in mind, one trick on V-bottom outboards, to get even less wetted hull, is to add a setback bracket to the engine.

[olivialyn11]

gents, dont you get it that he is most probably joking us ? you make here a brain storming for something that is nonexistent.

please show us some pics of your heavily modified 85hp pushing now nearly 130hp . what did you installed ? a supercharger?

no we milled out the sleves on the block and stuck larger pistons and sleves, it looks exactly like an 85, but has new rods and gears in the lower unit that we harvested form a 150

if we can eventually figure out a better exhaust system we might try to add a turbo... not sure because we would have to modify the fiberglass cover and probly part of the lower unit.

the same way my srock 119hp 4cylinder now pushes 400hp, with time and wasting money, got the power of a 130 motor with the weight of the 85, difference of 50hp with out the gain of 150lbs

I would like to see pics of how the engine (prop shaft and antiventilation AV plate) sit in relation to the bottom of the boat.

Putting the prop into dirty water by burying it even 1-3" will knock off some RPM.

Having it too high on a V bottom boat will kill bow lift. W/out bow lift, there is more wetted hull, which = drag.

Boats without a real serious V can simply err on the high side. The prop doesn't need to be low enough to produce bow lift. V-bottom boats don't have this luxury. They have a sweet spot, usually only 1 to 1.5" in height along a given range. For example: On a given V bottom boat, the prop shaft sitting 2" below the bottom might be perfect, whereas 3" below knocks off RPM/speed.

Given all the variables, I think this one needs to be cleared.

EDIT: at the end of the day, only running the boat on plane and looking at the lower unit to see where the AV plate sits in relation to the water matters. It should skim just at the surface (visible), w/ maybe a little splash going over it while under way at speed.

Also, since the OP seems to have speed tricks in mind, one trick on V-bottom outboards, to get even less wetted hull, is to add a setback bracket to the engine.

my goal is to get the motor mounted in the next 3 weeks, just finished re-glassing the boat and are prepping for paint, not sure what an av plate is but as soon as we get the alumium mounted to the transom and the motor hung ill let you know how far the unit sticks out.... i also came across a free bee prop its a 13-1/4x17 and its in near mint condish so i can probly use it for a test run as long as its the right shaft size havnt checked it yet...

[BonairII]

for all purposes the 85hp motor currently has 120 raw hp at the crank...

My guess is that the 85hp is getting 70-75hp at the prop(depending on how tired the motor is).

I've only skimmed this thread(the car talk got me derailed), but I'm guessing a 17pitch is probably a good starting point. You need an accurate tach on your motor to make ANY kind of educated decision on what prop to run.

Your motor has 10hp more than my '77 75hp motor...and you're boat is prob quite a bit heavier than my 16' fiberglass. I'm running a 17pitch and getting 5500rpm.

If you're loaded heavy, you may end up needing a 15pitch.

Keeping your RPM within the manufacturers operating range is very important....if you over-prop, you'll be lugging your motor.