[614847]

Just wanna float this one out there and see what kind of opinions I get...

What makes a better prop for running a small to medium size outboard boat in ocean swells, a higher pitch/smaller diameter or a lower pitch/larger diameter?

My reason for asking is that this summer I had my 22' Auquasport/200hp Johnson out of Freeport. I started out with a 14.5"/19 pitch prop (the factory reccomended). The motor seemed to surge greatly with this combo. Bogged in swells, cavitated off 'em. I later switched to a 15"/17 pitch prop and felt I had better response, albeit these days I went out were also slightly better conditions.

After running tests back in the Sound I found that the 19 pitch only gave me a WOT of 4800 rpm. The manufacture says that I should be between 5000-5500rpm. I switched to the 17 pitch and topped out at 5100 rpm. I know other people with the same setup and they run fine with the 19?
Back to my question, does anyone know why the same setup would run better with the 19 and mine the 17? And are there any suggestions for a prop that is used to run ocean swells as opposed to a chop in the Sound?

I'm would appreciate any experienced opinions. This was the first year I brought my boat out to the south shore. Had a great time, and will definitely do it again. Just gettin the boat to run well out there took some patience. But I made it past the HA, I was happy to get that far. I guess that's my limit till I get a slightly more seaworthy boat......

Thanks again....

 

[Scalawag]

Arent both of these wrong? The 19" @ 4800 is way low, the 17 @ 5100 is also on the low side. Id try another prop, aim fo 5300 @ WOT. Sometimes a little cup does the trick as well. Talk to guys at a prop shop thier experts.
Alan

 

[614847]

The 17 pops on plane quickly, and gives me 28 mph @4000 rpm. Any less pitch and I beleive I would loose too much top end. With the 19, I was at 31 mph, but sluggish getting on plane.

What I am really curious to know is what makes for a good prop in ocean swells? Are the considerations for an ocean going prop different from those used in the Bay or Sound?.....

 

[614631]

The pitch of your prop can be compared to the gear on your car or bicycle. The higher the pitch the higher the gear. Props with higher pitch may give you more top end if the engine can drive it but you will loss low-end torque and acceleration. Lower pitch props do the reverse. When selecting a prop make sure you do not pick one that will cause the engine to run pass red line or the WOT rpms recommended by the manufacture. My feeling would be if you are less concerned about top end speed but would like some additional torque and acceleration I would use the lower pitch prop. I don't spend much time in choppy water so I can't offer any personal experience on the subject, but my guess would be acceleration and torque are more important then speed in choppy water.

 

[Scalawag]

hey Ralph,
ya know what it might be? If the props " Blowingout" in rollers or swells then maybe the engine height needs adjustment. I had this happen to me 4 years ago on a new skiff I bought with a 50hp Johnson. The boats gotta be hauled and engines gots to be moved down a notch.
Alan