Prop for tournament 192 with 200 outboard

[TinkerinMatt]

Just opening a discussion since propping a boat is more of an art than a science. My 2000 FICHT 3.0 200 on a 1991 tournament 192 hull with a 14.5” x 19p viper prop did 52 on fresh water and 54 on salt. My dads 2002 3.3 big block 200 with a 14.75” x 19p viper prop does 54 on fresh water and 56 on salt on a 1991 tournament 192 hull, all numbers are mid July heat. Is it the prop? Is it the little extra power from a 3.0 to 3.3? Is it error in GPS readings? I don’t have the RPMs off the top of my head, but I’m curious if there’s anything left in either motor with a prop change, is 60 possible? Is going from a 14.5 to 14.75” prop that much more efficient (4%)?

Has anyone else gone faster, and have a recipe they’d be willing to share? My last resort is hacking the FICHT EMM and downloading the program from a 225 (which is on my to-do list).

 

[DennisG01]

There won't be an error in the GPS... or at least there shouldn't be. But... just off the top of my head, variables could be (and I'm sure more)...

-- RPM that each engine was turning at
-- Health/tune of each engine
-- Prop differences
-- Could even be differences in the engine power when two of the same motors (same brand/model).
-- Running conditions... altitude, current, wind, temp, etc.
-- Weight of the boat... gear, fuel, water logged hull/wood (this happens to all boats, to at least some extent). A couple hundred pounds can have a noticeable impact, especially on a small boat.
-- Hull condition
-- Motor height
-- Operating differences (trim, for example)

You can't do any serious talking about props without knowing your MAX RPM. But, if you're after speed, you've got the wrong style of boat.

 

[TinkerinMatt]

By gps error I was getting at how a FPS is speed over land but if there’s a current, your speed over water is different. Both boats the Speedo maxes at 50 so it wraps around a bit past 50. Motors are set at same height, same weight, same gear, neither hull is painted, both have around 450 hours. The 2002 is a 3.3 liter vs the 2000 is a 3.0 liter.

 

[glacierbaze]

Ten percent more displacement, and a bigger prop. 54 and 56 are basically the same, unless you are running side-by-side in the same sea state. Does his boat have the SV2 hull in '92?

 

[TinkerinMatt]

I am in topsail with the 3.3 boat and have an answer to the rpm question, it’s 6000. Do you think the slightly bigger prop really matters with the same pitch?

 

[DennisG01]

What's the RPM on the smaller engine? Can't really compare without that. And, of course, we have to "assume" that the tach is dead-on accurate...

But... you're chasing ghosts here. 2 mph can be explained by any one of a dozen, or more, things. WAY to many variables to try and settle on one thing. Even two identical boats with identical engines can run a couple MPH apart. Honestly, there is no real answer to this and it's only going to drive you crazy to try and figure it out.

 

[Parthery]

Was it chine walking at that speed?

I've never seen a Grady hit 60...got close to 50 once with my 205 but didn't quite make it.

Not going to editorialize here either, but that lanyard should probably be clipped to you and not the windshield.

 

[TinkerinMatt]

Boat is very stable at all speeds, doesn’t portpoise at all or walk. I know I’m chasing nothing but the engineer in me wants to explain everything, and the competitor in me wants to be faster than my dad.