Advise on possibly changing prop?

[chiroken]

2007 Maxum 1800MX bowrider, 2000lbs, Mercruiser Alpha 1 3.0L 135hp I/O. Current prop is I believe the factory prop 832832A45P21, 14 1/2 X 21, 3 blade.

I'm trying to decide if it's worth the investment to swap out props and just how much difference it will make. As well, the cost involved. The main reason I would switch props is to improve the hole shot.

The boat is used for overall recreation, abit of exploring but also to pull tubes (2 singles), waterskiers, wakeboarders. Mostly my immediate family uses it. 2 young kids @ 7 & 10 and I'm 185lbs. The boat will get me up on skies or wakeboard fairly easily. I notice the difference with my 200lb friend. He still gets up, not as easily though. Wasn't able to get up my 220lb brother on skis or wakeboard. Not sure how much of his lack of technique was involved. I can't see it being a huge factor on skis (2), he was fighting the boat on the wakeboard though.

How much of a significant difference should I expect by going to a 19 pitch? And a 4 blade prop will also improve the hole shot over a 3 blade? And the only downside is a loss of 2-3 mph on top end speed? (which isn't a concern to me, I usually run 4000-4200 rpm at approx 33-35mph).

I also don't quite understand the significance of prop and WOT. I found on this link http://www.marineengine.com/parts/prop/wot_prop.html that my WOT RPM's should be 4400-4800. For how long is it safe to run at these rpm's and what is a good rmp to run at for cruising for say 5-15+ minutes?

If I go down to a 19 pitch prop, my rpm's will increase approximately 300-400? Is this correct? Does this really make a difference if I'm not running full speed? I typically run at the numbers mentioned above for 2 reasons: 1) fuel economy and 2) it seems fast enough.

Thanks in advance for any advise.

 

[steelespike]

Re: Advise on possibly changing prop?

Without your max rpm and speed it is difficult to select a prop accurately.
I think a 19" 4 blade will vastly improve hole shot and low to mid range performance.
You may have to watch your max rpm,

 

[darcy4670ca]

Re: Advise on possibly changing prop?

I have a fourwinns 180, 135hp. It came with the same prop you talk about. the boat is a 2011, (http://s915.photobucket.com/albums/ac357/darcy4670ca/)
I talked a few people about this and to my surprise I was told by a boat modifer to go to a 19p highfive ss prop. Works so good. I hit 38mp at 4800rpm as the boat should. Hole shot is less than 4secs, trolling is great, and slow steering is excellent. You should some place that will let you try this prop out, its worth the bucks. (http://www.smwebhead.com/phpBB3/viewtopic.php?f=3&t=6388)

 

[bobhol]

Re: Advise on possibly changing prop?

I went from the 21 to a 19 on my Chaparral 180,3.0 merc and it made a ton of difference .The 21 was too much prop ...my engine went WOT from 4100 rpm to 4500 and felt much better thru the whole range .my 21 is a spare and if I could sell it I would like to try an 18 -4 blade..../Bob

 

[sethjon]

Re: Advise on possibly changing prop?

2007 Maxum 1800MX bowrider, 2000lbs, Mercruiser Alpha 1 3.0L 135hp I/O. Current prop is I believe the factory prop 832832A45P21, 14 1/2 X 21, 3 blade.

I'm trying to decide if it's worth the investment to swap out props and just how much difference it will make. As well, the cost involved. The main reason I would switch props is to improve the hole shot.

The boat is used for overall recreation, abit of exploring but also to pull tubes (2 singles), waterskiers, wakeboarders. Mostly my immediate family uses it. 2 young kids @ 7 & 10 and I'm 185lbs. The boat will get me up on skies or wakeboard fairly easily. I notice the difference with my 200lb friend. He still gets up, not as easily though. Wasn't able to get up my 220lb brother on skis or wakeboard. Not sure how much of his lack of technique was involved. I can't see it being a huge factor on skis (2), he was fighting the boat on the wakeboard though.

How much of a significant difference should I expect by going to a 19 pitch? And a 4 blade prop will also improve the hole shot over a 3 blade? And the only downside is a loss of 2-3 mph on top end speed? (which isn't a concern to me, I usually run 4000-4200 rpm at approx 33-35mph).

I also don't quite understand the significance of prop and WOT. I found on this link http://www.marineengine.com/parts/prop/wot_prop.html that my WOT RPM's should be 4400-4800. For how long is it safe to run at these rpm's and what is a good rmp to run at for cruising for say 5-15+ minutes?

If I go down to a 19 pitch prop, my rpm's will increase approximately 300-400? Is this correct? Does this really make a difference if I'm not running full speed? I typically run at the numbers mentioned above for 2 reasons: 1) fuel economy and 2) it seems fast enough.

Thanks in advance for any advise.

A 19 should take care of the problem with the heavier guys. If you do a 19 you will lose a little top end and the RPMs will go up as you mentioned.

 

[chiroken]

Re: Advise on possibly changing prop?

So I had the boat on the water this morning: just myself, 1/2 tank of gas, not too much gear (maybe 75-100lbs tops). WOT was 43.5 mph at 5000rpm's, 34 mph at 4000 rpm's. I believe as I mentioned earlier my target WOT range is 4400-4800rpm's. If I understand correctly, if I go to a 19 pitch prop I will increase my WOT rpm's approx. 300-400, taking me definitely higher than where I should. Is this significant in any way if I don't plan on being WOT? As I mentioned, I often run 4000-4200 rpm for periods of time of less than 10 minutes, at a speed of 32-34mph depending on boat load.

Any further comments?

Thanks.

 

[Oldskool]

Re: Advise on possibly changing prop?

I recently changed from a 21 pitch 3 blade PowerTech SS to an 18 pitch 4 blade aluminum; wanted to see how the 4 blade performed before investing in another SS. It is on a 2007 Sea Ray 210 Select with a 350 mag and Alpha drive. I was able to maintain my WOT rpm's and probably lost 2 mph. My hole shot is much improved, and allows me to get my son up on skis or wake board much easier. I'm also able to stay on plane at about 300-400 less rpm. You might consider going to either a 19 or 20 pitch 4 blade.

 

[walleyehed]

Re: Advise on possibly changing prop?

Stiletto baypro II is a good bet on that rig. The blade design allows a lot more lift than aluminum and also more bite. Just guessing at pitch is a lost cause due to design differences. Decide what you are willing to spend on a prop and use that as a starting point. The choice in pitch will differ with design and material as well as make.