Another Prop Selection Q

[98LSWON]

I have a 1993 18' Sea Ray 4.3LMerc w/ Alpha One outdrive. I bought it a few months ago. It came with a 15' x 17 pitch aluminum prop (3 blade). I researched and the boat originally came with a 13.75' x 21 alum prop. I get 4800 RPMs (max for the engine) with an extra inch of throttle and 39 mph on the gps. Should I go back to the original prop size or..... the guys at Powertech recomended a SS 4 blade 13.75 x 19 pitch stern lifting prop. I'm smart on pitch, but stern lifting is new to me. I plan on using the boat for slalom skiing and cruising with 3-4 people in the boat. Any suggestions.
I'm favoring a SS prop due to slightly better performance out of them, but # of blades and pitch seem to have too many variables, and there isn't anywhere near me that will demo a prop. I don't want to waste $400 on the wrong prop. Thanks.

 

[steelespike]

Re: Another Prop Selection Q

If your haulling all those people and skiing you don't want the 21.
The 4 blade prop would help your hole shot and no doubt a stainless will improve overall performance. When changing material,and style its more difficult to determine specific changes but you should be pleased with overall performance.I think something like smart tabs trim tabs is a better investment at this point.I believe they cost less and do more for you.Improve hole shot,stabilize ride,are said to increase speed,stay on plane at lower throttle and resist no wake speed wander.You might check the Hustler aluminum props They are said to give close to stainless performance at aluminum prices.

 

[MikDee]

Re: Another Prop Selection Q

I have a 1993 18' Sea Ray 4.3LMerc w/ Alpha One outdrive. I bought it a few months ago. It came with a 15' x 17 pitch aluminum prop (3 blade). I researched and the boat originally came with a 13.75' x 21 alum prop. I get 4800 RPMs (max for the engine) with an extra inch of throttle and 39 mph on the gps. Should I go back to the original prop size or..... the guys at Powertech recomended a SS 4 blade 13.75 x 19 pitch stern lifting prop. I'm smart on pitch, but stern lifting is new to me. I plan on using the boat for slalom skiing and cruising with 3-4 people in the boat. Any suggestions.
I'm favoring a SS prop due to slightly better performance out of them, but # of blades and pitch seem to have too many variables, and there isn't anywhere near me that will demo a prop. I don't want to waste $400 on the wrong prop. Thanks.

I'm confused here? You have a 17" pitch prop, and get 4800rpm with an extra inch of throttle? What does that mean? do you mean you have an extra inch of throttle left, even though you're already turning 4800rpm?
It sounds like you're Way underpropped!

It don't work that way, if that's the case. First, We need to know what rpm your engine turns at Full throttle! Take it out, and open it up, then give us that rpm, (it shouldn't hurt your engine for a short high speed run, just don't keep it there for 1/2hr or more like this). Then get back to us.

Chances are, from the info you gave us about the orig prop, and usually the average boat your size with that engine, the recommended 4blade 19" pitch would be Ok, But let us have all the info before suggesting a prop. What you want is a prop that will let your engine only reach 4800rpm at Full Throttle! with your average load.

 

[98LSWON]

Re: Another Prop Selection Q

Yes, I'm turning 4800 RPM (that is max recommended for the engine) with an extra inch of throttle movement to spare, I retard the throttle to prevent overspeeding the eng. The prop on the boat is 15' Dia x 17 pitch. I know it's underpropped, I'm just not sure what pitch prop to get once I change the diameter back to the original 13.75' and add another blade. It'll be about a week before I can get the boat back out because in this part of TX the nearest lake is 45 min away. I was hoping to have a new prop by then but I may just wait and think about it over the winter, its about time to put the boat to sleep for the year.

 

[Randybeall]

Re: Another Prop Selection Q

If you have throttle to spare then an increase in pitch is a must. The 19 in a 4 blade stainless would give you more bite at throttle up to pull a slalom skier up even with 4 people in the boat. The efficency of the stainless would help with keeping close to the same top speed while the 19 inch pitch would bring the engine rpm into line. That said, iboat has an exchange program on some props. You buy it try it out, if it is what you want good. If it is not quite right and you havn't damaged it you get to exchange for a cost which just covers freight. The second prop you receive may have been on someone elses boat but it is like new and they will stand behind it. Just don't take the boat to lake Wichita. It would look bad stuck in the mud like that and it would not make any difference what prop you were destroying.

 

[98LSWON]

Re: Another Prop Selection Q

Just don't take the boat to lake Wichita. It would look bad stuck in the mud like that and it would not make any difference what prop you were destroying.

I was running around the lake (running-running, not in the boat) and saw people standing up in the middle of the lake, i think I'll stay away from that one. I usually go to Arrowhead, or Waurika Lake if we are gonna go camping.