Need Prop recommendation

[carpking]

I have a 22 foot deck boat with an 8 foot beam. It has a 98 model Mercury 150Rx6 2 stroke outboard powering it. It currently has a 4 blade stainless steel prop on it...not sure of brand. I believe the prop has a spin hub bushing as it is turning at at a slower rate than the engine and I am losing about 30 percent of my top end speed. The numbers on the prop are 48 16318 21P. I can't afford 500 bucks for a new prop so I am looking for an affordable recommendation for my boat. The boat is used to pull tubes occasionally as well as a fishing boat. Never more than 4 or 5 people on the boat. Trying to stay around $250 bucks or less. Hoping current prop can be repaired. Thanks

 

[Sea Rider]

Without knowing achieved max wot rpm from current prop as max loaded expect to receive a wild theoretical answer. Now the bummer is: buy same exact prop, go for a less pitch prop to pull wot revs up to which precise wot rpm range ?

Who said boating was a cheap water sport to dial best top prop on first try for multiple recreational tasks...

Happy Boating

 

[dingbat]

why buy new?
Hubs are quick and easy to replace

 

[carpking]

why buy new?
Hubs are quick and easy to replace

I need a prop to run while the other one is being repaired and to also have an extra one for emergencies .

 

[carpking]

Could someone break down those numbers for me so I know what order if I order the same size? 48 16318 21P

 

[havoc_squad]

Not hard to find the specification for that prop, you do a quick internet search for what turns up using that part number, a little patient persistence and paying attention to detail will get you the info you need.

The part number you gave is universal enough that you will find the same specs of prop diameter, rotation, and pitch I believe for any props that use that number.

The internet doesn't work for all situations and sometimes not even forums, but very common parts such as you listed are very easy to pinpoint their specifications.

If you are running a Mercury/Quicksilver prop with quick replace Flow Torque hub kit, you simply buy the correct hub part number and swap it out.

I would recommend though first using a punch and making a mark on a non-critical area both on the hub and one the prop itself in one line to rule out spun hub.

https://www.youtube.com/watch?v=d7Lz7cI-srQ is probably an adequate video to demonstrate the concept.


Personally, I think your boat is over-propped with that 21 pitch for a 22 ft deck boat with only 150 HP outboard. Not to mention it is not number of people that matters, it is the total weight of the passengers, gear, fuel, etc that affects boat performance and safety.

However, you won't know for sure until you get the throttle within the max safe rpm range for wide open throttle defined in the owners/service manual with the typical gear and passengers onboard.

If the motor rpm stays stable in the "safe spot" for the max rpm range with the boat at optimal trim for best rpm & speed and the throttle is all the way, then that's the "sweet spot".

If you buy a prop pitch for the purpose of people towing, make sure those using the boat are trained to keep an eye on the tach and not exceed the safe max rpm.

There's plenty of good affordable new Stainless Steel prop solutions around but you're going to have to open the wallet a "wee bit more". Otherwise its aluminum only for your budget. (Past a certain high HP limit on use applications +200 hp, stainless steel becomes the only option).

 

[carpking]

The boat normally runs about 45mph according to GPS with 4 people and gear. However, the last several times out, max attained speed was around 30mph. The motor is running great. Doesn't bog down, no missing, etc. However, to be sure, checked spark and compression and all checked good. New plugs, new fuel lines, cleaned carbs and no change on top speed. I realize the hubs usually just go out, but I have run out of other possibilities for the slower speeds. The marinas resident mechanic said that he has seen hubs that slip slightly without completely failing. I'm open to any other possibilities. No extra weight or leaks on boat either.

 

[carpking]

Not hard to find the specification for that prop, you do a quick internet search for what turns up using that part number, a little patient persistence and paying attention to detail will get you the info you need.

The part number you gave is universal enough that you will find the same specs of prop diameter, rotation, and pitch I believe for any props that use that number.

The internet doesn't work for all situations and sometimes not even forums, but very common parts such as you listed are very easy to pinpoint their specifications.

If you are running a Mercury/Quicksilver prop with quick replace Flow Torque hub kit, you simply buy the correct hub part number and swap it out.

I would recommend though first using a punch and making a mark on a non-critical area both on the hub and one the prop itself in one line to rule out spun hub.

https://www.youtube.com/watch?v=d7Lz7cI-srQ is probably an adequate video to demonstrate the concept.


Personally, I think your boat is over-propped with that 21 pitch for a 22 ft deck boat with only 150 HP outboard. Not to mention it is not number of people that matters, it is the total weight of the passengers, gear, fuel, etc that affects boat performance and safety.

However, you won't know for sure until you get the throttle within the max safe rpm range for wide open throttle defined in the owners/service manual with the typical gear and passengers onboard.

If the motor rpm stays stable in the "safe spot" for the max rpm range with the boat at optimal trim for best rpm & speed and the throttle is all the way, then that's the "sweet spot".

If you buy a prop pitch for the purpose of people towing, make sure those using the boat are trained to keep an eye on the tach and not exceed the safe max rpm.

There's plenty of good affordable new Stainless Steel prop solutions around but you're going to have to open the wallet a "wee bit more". Otherwise its aluminum only for your budget. (Past a certain high HP limit on use applications +200 hp, stainless steel becomes the only option).

Over propped? What pitch do you recommend? I considered going to a 3 blade prop but figured since I tow with it, the hole shot torque was more important.

 

[havoc_squad]

10616651[/URL]]



Over propped? What pitch do you recommend? I considered going to a 3 blade prop but figured since I tow with it, the hole shot torque was more important.

Better hole shot is fixed with either more low rpm HP with good acceleration or less pitch of a good running engine. The hole shot improvement is probably not much with a 4 blade prop.

If the pitch calculation is accurate when downgrading to 3 blade, that would be a 23 pitch 3 blade prop.

14" x 19 pitch right hand SS 3 blade did fine with me on merc Alpha One Gen 2 140hp 16ft ski boat in skier hole shot, though I did have to pay attention a little to the tach on high speed runs near WOT to stay safe.

If I just planned on driving the boat around instead of pulling skiers out of the water, 14" x 21 pitch was probably best.

140hp 3.0L Sterndrive running 1.98 to 1 ratio gearcase versus 150hp outboard running 1.87 to 1 gearcase, so I would be primarily concerned with how much work the prop is doing per rotation on a boat that might be put under heavy load.

You're not putting on a more powerful engine, so the pitch has to be lowered to improve hole shot.

I would first suggest doing the test I mentioned if the hub can be fixed and then report your findings before making a buying decision.

Guesswork in buying parts just ends up costing you more at the end.

If it can't be fixed and is confirmed spun, spend the money for a prop with easy hub replacement. Solas makes some good budget SS props and there are info resources to ensure you get close enough to fit your outboard regarding max prop diameter.

If you buy the same series prop for a spare that uses quick hub replacement, you can quick swap hubs.