Brand New Boat Owner- Prop Question

[Coloradomedic]

Hello!
Just bought my first boat and the last owner told me that he paid 900 for the prop. I paid 4k for the boat, trolling motor, and fish finder. Call me crazy, but I'm thinking I should buy a cheap prop and install it while I'm learning how to drive a boat. It's an 18' Invader with a Mercury Black Max 150 outboard V6 Motor. (Serial OD178421)

The prop that I have on it now is a High Five- Part number 48-815758-19. I believe that it's a 13.25" x 19 pitch prop. Any advice on buying a prop to learn on? Look for the same size and pitch? Go with a different size, pitch, # of blades? I really don't understand how the pitch and diameter can or cannot vary on a motor, so any advice would be appreciated.
Thanks for the help!

 

[briangcc]

I'd run it as is and get it repaired if/when you hit something. We all hit something with a prop at some point...sunken logs, rock piles just below the surface, etc. Some hits are avoidable, others come out of no where.

In a nutshell pitch is related to the theoretical distance it will travel in 1 full turn. So in a perfect world, a 19 pitch prop will travel 19" forward on one full rotation.

More pitch takes more HP to turn it (and gearing) which can take you out of the operating range of your motor. Each motor has a RPM range its spec'd to run in. If you go below the lowest number, you're lugging your motor causing it to work really hard and will shorten its life. If you go above the upper number, you're running the risk of the top end coming apart - pistons, rods, etc. Aim for the middle of your RPM range with a typical passenger load and you should be good.

To go faster, typically, more motor is required...in some instances alot more motor for just a few mph.

 

[Stinnett21]

How do you anticipate using the boat? High Five is typically a hard core pulling prop, ie. skis, wakeboards. Usually you see them on family bowrlders who haven't pulled the trigger on a tow boat yet. If that 's not your gig and you want to start slow and cheap, visit the Turning Point Propeller web site and use their prop selector tool. Mercury has one to but even their cheapest props will be a bit more expensive. That may get you in the ballpark.

 

[airshot]

900 for a prop ?? I think the previous owner might have done some exagerating...

 

[Coloradomedic]

How do you anticipate using the boat? High Five is typically a hard core pulling prop, ie. skis, wakeboards. Usually you see them on family bowrlders who haven't pulled the trigger on a tow boat yet. If that 's not your gig and you want to start slow and cheap, visit the Turning Point Propeller web site and use their prop selector tool. Mercury has one to but even their cheapest props will be a bit more expensive. That may get you in the ballpark.

I'm going to be splitting time between fishing and tubing with the grandkids. Waterskiing in a few years if I still have the boat.

 

[Coloradomedic]

900 for a prop ?? I think the previous owner might have done some exagerating...

Possibly, but I've seen it listed for over 800 on numerous websites like this one:

Mercury High Five Stainless Steel (13.3" x 19") RH Propeller, 815758A46 8M0151291

MerCruiser Exhaust Manifolds, Engine Parts, Outdrives and Outdrive Parts, Watersports and more!

powerboatsupply.com

Either way, it came with the boat. I'm just looking for advice on getting a spare prop.

 

[Scott06]

Hello!
Just bought my first boat and the last owner told me that he paid 900 for the prop. I paid 4k for the boat, trolling motor, and fish finder. Call me crazy, but I'm thinking I should buy a cheap prop and install it while I'm learning how to drive a boat. It's an 18' Invader with a Mercury Black Max 150 outboard V6 Motor. (Serial OD178421)

The prop that I have on it now is a High Five- Part number 48-815758-19. I believe that it's a 13.25" x 19 pitch prop. Any advice on buying a prop to learn on? Look for the same size and pitch? Go with a different size, pitch, # of blades? I really don't understand how the pitch and diameter can or cannot vary on a motor, so any advice would be appreciated.
Thanks for the help!

Depends on your boating skills and where you boat. If there is shallow water or debris like in a river probably a good idea as not only protects the expensive SS prop but also Aluminum is easier on the gear case if you have a strike than SS.

Something like a Merc Black Max, Michigan Vortex etc one of the entry level Al props would work. As to others mentioned down in pitch makes the engine go up in RPM, up in pitch vice versa. You want the engine to be within the specified rpm range for it. Not that you have to run it WOT all the time , just if the engine can get the boat there it is propped correctly.

being new to boating if you want to try props I would suggest you find a local marina or prop shop that will allow you to swap props. Going from 5 to 4o or 3 blades can make a difference. Some on line places Like Prop MD in the midwest I think allow you to exchange pitches.

 

[QBhoy]

High 5 props (in my opinion) have their use. But one use only. That would be for giving a best effort at pulling people out the water, from a typically either underpowered boat or a boat that’s not designed for it.
Outwith this use exclusively, they fall way far of the mark in every other department.
Simply outrageously terrible, in terms of efficiency, general use, prop slip and top end. Pretty much everything apart from pulling people out the water. Very commonly used on your average 17-19ft bowrider of a generic type, with a 3.0 etc etc. where to be fair, they allow a decent effort at it, where otherwise or without, wouldn’t be too great at things.

Without going on about it too much…when it comes to absolutely everything else you want the boat to do…shockingly bad. I literally couldn’t believe the data I collected from one recently last year. The prop slip was unbelievable at the top end. I compared it to two 3 blade props which were 2 inches less pitch. Despite this..the rpm figures in proportion to the speed figures recorded between the high 5 and the two other props..was sky high all the way through. The most astonishing thing, was the prop slip at the top end. Showing just under 28% slip.
There was a 6-8 mph drop from the 3 blade props of two inch less pitch.
But. If you only want water sports…worth a try.
I might also add that the pitch you have, might require some caution for sure. Keep an eye on those rpm at the top end. I’d be almost certain, given the mentioned example above around their behaviour..and the pitch you actually have, it’s way under propped in the first place. A 19” high 5 would act fairly similar in rpms to a normal prop of less pitch. A lesser figure of pitch like a 17” would be almost unheard of on a 18ft boat with that engine. Best of luck.

 

[Coloradomedic]

High 5 props (in my opinion) have their use. But one use only. That would be for giving a best effort at pulling people out the water, from a typically either underpowered boat or a boat that’s not designed for it.
Outwith this use exclusively, they fall way far of the mark in every other department.
Simply outrageously terrible, in terms of efficiency, general use, prop slip and top end. Pretty much everything apart from pulling people out the water. Very commonly used on your average 17-19ft bowrider of a generic type, with a 3.0 etc etc. where to be fair, they allow a decent effort at it, where otherwise or without, wouldn’t be too great at things.

Without going on about it too much…when it comes to absolutely everything else you want the boat to do…shockingly bad. I literally couldn’t believe the data I collected from one recently last year. The prop slip was unbelievable at the top end. I compared it to two 3 blade props which were 2 inches less pitch. Despite this..the rpm figures in proportion to the speed figures recorded between the high 5 and the two other props..was sky high all the way through. The most astonishing thing, was the prop slip at the top end. Showing just under 28% slip.
There was a 6-8 mph drop from the 3 blade props of two inch less pitch.
But. If you only want water sports…worth a try.
I might also add that the pitch you have, might require some caution for sure. Keep an eye on those rpm at the top end. I’d be almost certain, given the mentioned example above around their behaviour..and the pitch you actually have, it’s way under propped in the first place. A 19” high 5 would act fairly similar in rpms to a normal prop of less pitch. A lesser figure of pitch like a 17” would be almost unheard of on a 18ft boat with that engine. Best of luck.

I really appreciate your input. Can you give me some ideas on which size props to use?

 

[QBhoy]

I really appreciate your input. Can you give me some ideas on which size props to use?

Be a brave man that suggests an exact prop type and pitch, for a boat unknown to him personally. Even at that, a few more details would be useful too. Even after that..assumptions are a dangerous thing. Props just have a habit of not playing by the rules in general. Tell me more about the boat and any performance, rpm and anything else you might have an idea of. I’d again, be just about certain that if you opened the throttle you n that lovely engine of yours..and kept it open for not too long…you might just have that engine screaming beyond its design. Unless your boat is a particularly heavy thing or not of a conventional shape perhaps. I’ll look her up now.

 

[Coloradomedic]

Be a brave man that suggests an exact prop type and pitch, for a boat unknown to him personally. Even at that, a few more details would be useful too. Even after that..assumptions are a dangerous thing. Props just have a habit of not playing by the rules in general. Tell me more about the boat and any performance, rpm and anything else you might have an idea of. I’d again, be just about certain that if you opened the throttle you n that lovely engine of yours..and kept it open for not too long…you might just have that engine screaming beyond its design. Unless your boat is a particularly heavy thing or not of a conventional shape perhaps. I’ll look her up now.

I live in Colorado. We just got 2 feet of snow dumped on us. I haven't even had a chance to take her out yet. The only time I've seen the motor run is in a driveway with a hose and earmuffs connected. Can't wait for summer!

 

[airshot]

Keep saving tour money for boating season....it is an expensive hobby !! In most cases, folks loose interest due to expenses of a boat, or, the others are not willing to spend the time and money for proper maintenance and upkeep and their boats fall apart sitting on a trailer in the backyard.

 

[Stinnett21]

Don't worry about your High Five. Just get on the water, become familiar with what you have and enjoy the situation!

 

[jlh3rd]

Hello!
Just bought my first boat and the last owner told me that he paid 900 for the prop. I paid 4k for the boat, trolling motor, and fish finder. Call me crazy, but I'm thinking I should buy a cheap prop and install it while I'm learning how to drive a boat. It's an 18' Invader with a Mercury Black Max 150 outboard V6 Motor. (Serial OD178421)

The prop that I have on it now is a High Five- Part number 48-815758-19. I believe that it's a 13.25" x 19 pitch prop. Any advice on buying a prop to learn on? Look for the same size and pitch? Go with a different size, pitch, # of blades? I really don't understand how the pitch and diameter can or cannot vary on a motor, so any advice would be appreciated.
Thanks for the help!

You said you were new..did you read this?
ESSENTIAL DATA REQUIRED
When posting a question about propellers, you cannot get a reasonable answer unless you provide the following information in your post: Items 1-4 are essential for meaningful response to most questions.
1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight....

general rules of thumb:...repeat, "general".
for every 1" increase in pitch, or diameter, the WOT rpm will decrease by 200+/- rpm. Of course the opposite is true.
For every additional blade, the WOT rpm will decrease by 200+/- rpm's.
So, on paper, getting the same pitch and diameter but removing one or two blades will increase your WOT rpm...
An aluminum prop that is the same exact size of a SS prop supposedly gives higher rpm's because it flexes......
The basic idea is to have rpm's at WOT in the specified engine operating rpm range.
You said you were new, so understand:
there are also various blade designs from manufacturers that also individually affect rpm's ...such as "cupped" props.
Also , as in my merc's CT engine, the gearcase diameter is larger than standard, so a prop may fit but will not work if it isn't made for that gearcase.
....sound simple enough?.......
I've kept performance #'s on 3 props,... 3-16x13(merc)...3-15.5x13(solas).....4-14x14(merc). All give practically the same #'s.

Personally, I believe an aluminum prop can give added protection over a SS prop with an underwater strike....
you're not crazy.

 

[JimS123]

1. Take a boater safety course.
2. Buy a chart of the waters you intend to boat in and memorize it.
3. While on land raise the engine to that the prop is bellow the bottom of the boat and note the position. When at or near the launch ramp go very slow and raise the motor to that position so you don't hit the bottom.
Watch your depth finder and don't go fast or lower the motor until you have verified that you are in deep water.
4. Drive the boat out in open waters and see if it performs to your liking.
5. Do a performance curve (chart speed vs. rpm) and verify that your current prop meets the engine's specified rpms. If all is OK you don't need a new prop.

 

[flashback]

Some local dealers will let you exchange props if bought new and undamaged. My local merc dealership does it.