3 blade vs. 4 blade question.

[ahicks]

I'm re-powering a 24' pontoon boat with a 90 hp Honda. Have never run a 4 blade prop. The boat will be used for 95% cruising, usually not far off an idle. The 5% will be for pulling the grand kids, under 100lbs, and likely at wide open throttle. Pretty familiar with what to expect there.

I'm also familiar with the process for finding the correct pitch using a 3 blade prop (looking for max rpm on a lightly loaded boat), and assuming no change when going 4 blade (same process).

My question is for those that have run both 3 blade and 4 blade on similar rigs, and all else being equal with properly pitched props, what differences will I notice one vs. the other? Is this going to be something I'll see and feel easily (with my butt dyno), or will I need to study the tach and GPS to see the difference?

IS THE 4 BLADE WORTH THE EXTRA MONEY?

Please, this is not a ski boat or a big block Donzi. It's an old man's pontoon boat! There was a day when I cared about results for those type boats, but that's a day long ago.

Thanks for your thoughts! -Al

 

[ajgraz]

My old trihull (not a pontoon, but might as well be, as it is basically a block in the water) benefitted from better hole shot, ability to get on and hold plane at lower rpm, and better fuel efficiency at cruise when I switched to a 4-blade. Did give up 1 or 2 mph at wot.

I plan to get a 4-blade for my newer CC.

 

[Sea Rider]

Before playing with props must know max wot achieved as usually loaded on calm water cond with current prop. Will know if OB is revving at safe wot rpm, that's between min and max wot rpm range. For that will need a tach, does toon count with one ? Check wot rpm factory range for that 90 beforehand testing.

Happy Boating

 

[rphillips]

Back to what ahicks asked. Thanks ajgraz. All else being equal, same boat, same weight, what will be the differences in a, say, 3 blade Hustler Turning Point vs. a 4 blade Hustler Turning Point? what should the difference be, hole shot, max. mph, wot rpm & should it be a noticable difference or will it so suttle, you may not even notice?

 

[ahicks]

Thanks rphillips! We're on the same page, but in order to keep it as simple as possible, I'd prefer not to even get in to prop brands/models at this point. If it turns out there are noticeable differences that justify the price, then I'll be tracking down more specifics. .

If somebody has actual 3 blade vs. 4 experience on a pontoon with a mid size engine, I'd surely like to hear your thoughts/impressions on the differences between them!

At this point, at the performance levels we're talking about with this size engine/boat combo, I'm more than a little skeptical regarding being able to justify the 4 blade. More curious than anything else.

-Al

 

[H20Rat]

Assuming your prop that you are running now is well suited to the load, you won't notice a difference... (no mention of WOT RPM, that is important, even more so in a pontoon that spends its life idling around) If you need a spare prop, then go to a 4 and keep your current as a spare, otherwise, leave well enough along and spend money on gas or a new water toy for the grandkids instead!

 

[Sea Rider]

Yep, if with no posted wot rpm as currently loaded won't know if OB needs a prop maximization and by how much usually speaking. If OB doesn't count with one buy an induction tach to check that out, are cheap, money well spent. Will expand your nautical horizon.. Which brand & HP is it, it's 2 or 4 strokes OB ?

Happy Boating

 

[ahicks]

Sea Rider,
Second sentence, original post:
"I'm also familiar with the process for finding the correct pitch using a 3 blade prop (looking for max rpm on a lightly loaded boat), and assuming no change when going 4 blade (same process)."

I didn't want this to be a discussion/exercise regarding how to properly select a prop. I'm VERY familiar with that process! This question is about 3 vs. 4 blade props on a pontoon boat with a medium size outboard. What, in your experience, should a person expect with one vs. the other?

If you must have a tach reading to get past that and answer the question, use 5700rpm (300rpm under manf's max rated) and about 24mph.

Smokingcrater, thanks for your opinion.

 

[Sea Rider]

Sorry Ahicks, so experience whatsoever with 4 blade alum props, all my experience is with 3 blade OEM props, have found with tach that all my 3 OB's were over propped by 1-2 pitches. New less pitch props are in the way..

Happy Boating