17' bowrider, 12 degree deadrise, 1978 GM Inline 6, 165hp I/O, drive gear ration 1.65:1, current prop:15 1/2" x 19 3-blade aluminum.
2 people and gear puts the total boat weight between 2400 and 2500 lbs.
Max RPM at WOT: 3900-4300
Ran the boat on the river and got these numbers:
(GPS speed, tach rpm)
28.2 mph at 2400 rpm
29.1 mph at 2600 rpm
31.5 mph at 2800 rpm
34.6 mph at 3000 rpm
37.0 mph at 3200 rpm
39.6 mph at 3400 rpm (WOT)
All the info I've read tells me idealy my WOT rpms should be near top of my engine's WOT range. My test numbers indicate i'm 900 rpm below that
I was planning on purchasing a 17 pitch prop to bring my rpms up, but that would only raise it 400 rpms, correct? That won't even get me to the low end of my engines rated rpms. Should I consider dropping down to a 16 or even a 15 pitch? Seems like a HUGE change from my current 19 pitch.
Engine is tuned properly, compression good, plugs, cap, rotor, carb, all in good working order.
Do these numbers look WAY out of whack to you guys? Any input would be appreciated.
2 people and gear puts the total boat weight between 2400 and 2500 lbs.
Max RPM at WOT: 3900-4300
Ran the boat on the river and got these numbers:
(GPS speed, tach rpm)
28.2 mph at 2400 rpm
29.1 mph at 2600 rpm
31.5 mph at 2800 rpm
34.6 mph at 3000 rpm
37.0 mph at 3200 rpm
39.6 mph at 3400 rpm (WOT)
All the info I've read tells me idealy my WOT rpms should be near top of my engine's WOT range. My test numbers indicate i'm 900 rpm below that
I was planning on purchasing a 17 pitch prop to bring my rpms up, but that would only raise it 400 rpms, correct? That won't even get me to the low end of my engines rated rpms. Should I consider dropping down to a 16 or even a 15 pitch? Seems like a HUGE change from my current 19 pitch.
Engine is tuned properly, compression good, plugs, cap, rotor, carb, all in good working order.
Do these numbers look WAY out of whack to you guys? Any input would be appreciated.
