Speed/RPM Questions

[omar174]

I have a Honda BF-115 on my 19 foot Hurricane Fundeck. With the current prop that I think needs replacing since it looks beat up (unknown make/model/pitch) the engine only revs to 5000 rpms and tops out around 30-32 mph on gps. I'm ok with that, but according to the owner's manual, the motor can safely rev up to 6000.

If I got a prop to rev the motor up to 5500-6000, how much speed would I pick up? I realize there are probably many variables, but does anyone know a ballpark?

[omar174]

And not that it has anything to do with the subject, but here is a pic of my boat.

[DRock]

Have you tried taking the prop off yet to see if there's anything stamped inside the hub? Sometimes they'll put some numbers in there, but you may have already checked. You could probably pick up a mph or two and the motor should have better acceleration with less pitch.

[tms0425]

If you can find out the pitch of your prop, then the Mercury prop slip calculator will give you a good idea.

http://www.mercuryracing.com/propellers ... ulator.php

It uses rpm (5000), speed (30-32), gear ratio (2.14:1 on yours), and propeller pitch to calculate prop slip. Then you can adjust the pitch and determine what to expect. It really boils down to how fast your engine will turn it with more pitch but there are many other aspects for performance besides the big number. 5000 is definitely too low for the Honda.

[badmoonrising]

Welcome ! Where are you in Maryland ? Upper bay here...

[omar174]

If you can find out the pitch of your prop, then the Mercury prop slip calculator will give you a good idea.

http://www.mercuryracing.com/propellers ... ulator.php

It uses rpm (5000), speed (30-32), gear ratio (2.14:1 on yours), and propeller pitch to calculate prop slip. Then you can adjust the pitch and determine what to expect. It really boils down to how fast your engine will turn it with more pitch but there are many other aspects for performance besides the big number. 5000 is definitely too low for the Honda.

Thanks. I'll have to try and see if I can see any numbers stamped.

[omar174]

Welcome ! Where are you in Maryland ? Upper bay here...

Ocean City. I had a pontoon for a couple of years. Good boat, just got bored with it and thought I would try something else so I bought this deckboat. So far so good, but I def. don't rule out another pontoon.

[BobG]

With the right prop, you should be able to go 80 miles per hour!

Oh, in other words, I haven't got a clue, but I really wanted to post SOMEthing here, so you win!!!

[Bamaman]

Call Hurricane's customer service department and ask them what the best overall prop would be for your boat. Or, check if you can find a Honda outboard dealer that sells Hurricanes.

Being a full hulled boat, they're just a little different from pontoon/tritoons.

[rbiederwolf]

I had similar problem, went from 5200 rpm to 6000 at WOT, gained about 2 to 3mph.

More importantly, you need to get in the max rpm range at WOT. Running the engine that low rpm at WOT will hurt the engine long term. They want to run in the desired range. I would think there has to be a number somewhere on the prop. If not take it to a prop shop or your dealer and have them check it.

My engine was a 115 mercury 4 stroke, manf recommended 58 to 6200 rpm at WOT. The original prop was a 13p 14 diameter. I dropped to a 12p 14 diameter and brought it up to 5600 rpm. I then dropped to a 11p x 14diameter and brought rpm up to 6000 rpm. My boat actually ran a touch faster with the 12p, but I used the 11p most of the time, since the rpm was a better number for the desired range.

[omar174]

I looked at the prop and the only markings I could find were d3x1325x17L, no brand name on it. I'm going to assume this means 3 blade, 13.25 diameter and 17 pitch. Like I said before, the motor is only spinning to 5000 rpms. I was thinking a 15 pitch would work better. Thoughts?

[curtiscapk]

15 pitch would but you at 5400 a 13 pitch around 5800. Not sure what it the top of your range is though.