Mercury & Pontoon boat prop guidance

[halmc]

Just installed a 2005 three cyl 40 hp EFI Mercury four stroke on my 18' Bass Buggy Pontoon. Happy with everything except to my ear (no tach) it's turning in the mid 4000's at full throttle. On the other end of the scale, at idle and in gear, the boat goes a bit fast for close in handling. Seems like too much pitch. The engine was installed when new on an aluminum ~19' fishing boat with tiller steering. Much faster and lighter than my grandpa-style pontoon.

So, it came to my hands with a prop that bears this number: 48 816706A40 14P. Do I infer correctly that this is a prop with 14" PITCH?

Assuming that the pitch is 14" I'd like to try a 12" pitch. Would that be a simple matter of looking for a 48 816706A40 12P?

Bonus question: is there a difference between "big foot" props and non-"big foot" props.

Thanks!

 

[ahicks]

Ist, I'd invest in a tach.
2nd, yes, safe bet that's a 14p
3rd, a 12p would likely be much closer, but may still be too much if looking for max performance.The only way to know for sure is a tach reading.
4th, no doubt the Bigfoot lower units use a different prop. They have different gear ratios, are set up for larger diameter props.

Sweetheart combo once you get it all dialed in, for sure!

 

[Sea Rider]

You must have a musician ear to say that current OB is revving at 4 K LOL. Buy a tach as suggested to dial best prop for your current application and load.

Happy Boating

 

[GA_Boater]

halmc

No idea who this was directed to, but using the flag option doesn't send the message.

Code: thank you for the rare on point answer. I'm. Pretty sure I can get the RPM within two 300 RPM, because I have a very simillar engine with a tach.. I especially appreciate the Bigfoot part of your answer

 

[Scott Danforth]

I have been around motors all my life, professionally and personally...... I dont know of anyone that can accurately tell rpm's by sound

Get a shop tach or a dash tach

 

[halmc]

I have been around motors all my life, professionally and personally...... I dont know of anyone that can accurately tell rpm's by sound

Get a shop tach or a dash tach

Thanks for answering a question that wasn't asked, and for failing to answer those that were.