I need Prop and Gearing Advice

[Swamp Thing]

I just read the posts in the Killer Prop topic. I am getting ready to reprop and regear my boat. My boat is a 15 X 8 Alumitech with a 454/425 hp and a 2.09 Stinger Gear drive. The boat seats five and I usually run with 4 or 5 people. Right now my boat turns 4900 RPM on the trailer with a 4-blade narrow Sensenich and a 2.09 gear. It will maintain a plane at 3000 RPM. I want to lower prop noise and increase low end push (I assume this will help with running dry). At the BC airboat show yesterday, I talked to Dave at Water Walker and Don at Sensenich. They both gave me similar advice which is to go to a 2.38 gear with a 2 Blade Sirus (WW) or a S series (Sensenich). The S series its similar to the Q series but for reduction units. What do you guys think? A lot of people are talking about a 2.68 gear but are all running small blocks on smaller boats. Should I go to a 2.68? If yes, how many blade prop?? Dave at Alumitech said he could regear my current drive to 2.38, but I am not sure about regearing to 2.68. Let me know what you think.

 

[John C]

Geoff, I have a 15x8 apache with a 500 caddy, 450 HP with a rotator gearbox. I changed my gear ratio from a 2:12 to a 2:37 and went from a 3B Waterwalker falcon to a 3B maximus. with the 2:37 I was able to turn the 3B maximus @ 5100 RPM with the prop set at the factory start mark. I set the pitch so it runs at 4600 rpm. caddys seem to like to run better at a little lower rpm because of thier tq. curve. The boat is quieter, it cruises at about 500 rpm less than with the 2:12, and I got about 3 MPH more on the top end. It does run dry a little better but it is not a WOW! difference. But the boat ran real well dry before the gear change. Priority1 just set up a 15x8 DB with a 460 ford with a 2:37 and a new sensenich 3B ultra wide. This is the only boat I have seen run with the new sensenich ultra wides. runs very quiet. I hope to try his blades on my boat next week so I can compare apples to apples on the same boat at the same time, same conditions. If I can get this done I will post my findings.

 

[fatboy0054]

JOHN IS RITE MORE GEAR BOX IS THE WAY TO GO NOW DAYS ! WIDE BLADES ARE THE FUTURE IN OUR DEAL ! SLOWING THE PROP DOWN JUST MAKES THING SO MUCH EASIER ! I GOT THE SAME SET AS JOHN EXCEPT I GOT A 2.3 WHIRLWIND PROP !SEEMS TO BE A GOOD DEAL !

 

[a1mudpuppy]

I just put a gear box on my caddy. The airboat shop was telling me that I needed to stay with a 1:77 but cntry141iq and Stan talked me into going with a 2:38 which is great. I'm glad thay did,!!!!
It will be better when I get a Master Blaster 2.3 for my Whirl Wind hub. I max out at 4000rpm I didn't want to go any higher with a caddy.

If I was you I would go with a 2:68 and a Sensenich Super Wide like Cntry141iq runs on is Alumitech.

 

[Waterthunder]

Finally I have been preaching higher gearbox ratios for 7 years now, it's finally coming around. You can cruise and plane at lower Rpm's with a higher ratio gear box just swing more prop and pitch. Just because you run a 2.68 doesn't mean you must turn 6,000RPM.