Trouble getting on plane

[BigPineKey]

I have a 12 foot Whaler type fiberglass boat that weighs 390 pounds with a 4 stroke 25 horse 2001 Honda. I bought it and used it at sea level where it ran great and would plane with 2 adults and a boy in it..I took it home to 6000 feet and it won't plane with two people, barely with one. It had a a 10 pitch prop, though manual calls for 12, I installed an 8 pitch prop. . The 8 pitch prop increased WOT rpm from 3180 with the 10 pitch to 3500 but still wouldn't plane with two people. With one person and the 10 pitch the WOT rpm was 3810 and it did get up on plane. Is there any way to get this boat and motor combo to plane with two people at 6000 feet? Manual says 25 horsepower at 5500 rpm. I had the carbs cleaned and synched ($300) It starts and runs great, just won't plane Goes 9 mph at 3500 rpm with two people with the 10 pitch

Don't want to rejet because it would cost $300 and I would have to to rejet again to go back to sea level.

I sold a 15 foot aluminum with 25 horse two stroke Merc and it would plane with three people in it at 6000 feet.

 

[Sea Rider]

Welcome to Iboats,

Seems 4 strokes OB's dosent like working at altitude. Assume removing carb is a pita on a 4 strokes compared to a 2 strokes one. If plan boating frequently at altitude will need to buy a carb jet kit for that altitude if available, or swap a complete converted carb when there,

High altitude jets along less pitch prop compensates for poor OB performance. If don't want to change carb jets, will need to go less in pitch or maybe a 4 blade less pitch prop, check which ones are available.

Happy Boating

 

[BigPineKey]

thanks

 

[gm280]

:welcome: to iboats. Always glad to have a new member...

I understand you probably don't know much about OB engines. But when owning a boat, you really should buy the factory shop manual for your engine and start reading and learning. So many things that you presently think are beyond your ability are really not that hard to do. And if you continue owning boats, you really should venture into general maintenance and carb rebuilding as a minimum. Once you do those things, it really isn't that difficult and I believe you would enjoy it as well. JMHO