What prop pitch do you guys run on your 120/140 I/O's?

[Starcraft Enterprise]

For an experiment today, I swapped the prop on my Mercruiser 120 I/O powered 18' Starchief from a 19 pitch to a 21 pitch. I noticed no difference on take off and getting on plane. At top speed I went from GPS confirmed 35 mph with the 19 pitch to 38 mph with the 21 pitch. My tach stopped working a while back but the engine definetly sounded alot happier and not like it was running on the ragged edge of destruction. I could actually cruise at 35 mph now and not feel guilty.
I guess now I will have to keep an eye out for a 23 pitch prop. Better fix the tach before doing that experiment.
Any of you guys running a 23 pitch prop with the 18' hull and the 120/140 I/O?

 

[elkhunter338]

Re: What prop pitch do you guys run on your 120/140 I/O's?

I am running a 21' boat with a 4 blade pro-pulse adjustable prop.
At this time I run 14.5" dia blades, at 15 pitch. Top speed 27mph at wot.
I cruise at 20 mph, engine sounds good. Tach says 3900 rpms at wot, but I suspect the tach is wrong, the engine sound like it is reved up at wot. I will find out what she revs with a new tack this summer.

 

[Pugetsound]

Re: What prop pitch do you guys run on your 120/140 I/O's?

I run a 14 1/2 - 21 pitch with my 22 holiday and push it with a 200 Johnson. Cruse at 25-30 and will top out a bit over 50. I would think a 23 will be to much 38 is a nice speed for the 18 you have. I never use all my power unless a smart a-- trys to play games with it on the River. LOL

 

[sabastianunf]

Re: What prop pitch do you guys run on your 120/140 I/O's?

ive got a 120 mercruiser on a 19 ft cuddy cabin - see pic in avatar - this boat is a lot heavier than most since it is old and has the cabin - it runs well with a 19 pitch 3 blade prop. I wakeboard a lot so I am currently running a 15 pitch 4 blade for the best hole shot when pulling a wake boarder and it rev up to about 4300 rpms and tops out around 27 mph - I have had it over 30 mph with the 19 pitch 3 blade prop but it took a while for it to get up to plane and the RPM's were a little on the low side @ 3800 - 3900. definately need a good tach before you start playing with props or else you can over rev the motor.

 

[jimbo_jwc]

Re: What prop pitch do you guys run on your 120/140 I/O's?

Wild fastest , funnist boat I have owned , read on net it has unique hull it's a three speed . 1987 Thompson 196 Sea Rage 196 CC 130 hp 3.0 liter Mercruiser Alpha One I/O 14.5" X 17P have seen 5000 rpm . Also now jet skis apear to jump wake and can open it up and leave some of them couldn't do with old boat

48-78118-a40-17p prop so IT's 14.5" X 17Pitch still don't know if its cupped or not but was told its orignal

 

[sbart]

Re: What prop pitch do you guys run on your 120/140 I/O's?

i have a 17' invader bowrider. 2.5 mercruiser 120hp.
Just rebuilt the alpha1 and replaced all the seals and gaskets on the motor.The motor look new from the inside. Maybe 3000 miles on it.
Before all the work i was achieving 35kph @ 4300 rpm WOT prop is a 19pitch 4 blader
Now with the same prop, its at 49kph @ 5000rpm WOT.
Is 5000 too much? Will it harm the motor? What is the correct rpm for this motor.
Thanx

 

[not enuf toys]

Re: What prop pitch do you guys run on your 120/140 I/O's?

I guess now I will have to keep an eye out for a 23 pitch prop. Better fix the tach before doing that experiment.
Any of you guys running a 23 pitch prop with the 18' hull and the 120/140 I/O?

what outdrive or better yet what gear ratio do you have? that just sounds like a lot of prop to me...

nice to see more ohio boaters on here!!