EricM
Well-known member
As had been previously reported, I changed engines on my 19-1/2 ft long, 8 ft wide semi-vee tunnel hull center console bay boat. I replaced the Honda 90 with a Johnson 150.
The 21" prop I had was too much, (4000 rpm, 30 mph, porpoise with much up trim at all) so I dropped to a 17" stainless, and attached a hydrofoil. Tried it out today with the following results:
IMMEDIATELY jumps on plane.
Hits 30 mph in seconds with full down trim.
Slight up trim gives 35 mph and 4400 rpm, but porpoise starts here.
More up trim runs rpm quickly up to 4800, and likely considerably higher, but porpoise beats the crap out of the boat (and me) before I can actually approach the max possible rpm.
Motor can be lowered 2" yet.
No jack plate. Would one help eliminate the porpoise? If so, how big would you think it would need to be?
Will an even lower pitch prop help?
Suggestions (about the boat!!) are welcome. She's totally fishable as is, but I'd like to adjust the wrinkles out of the set-up and make her effecient, solid, and faster.
Thanks, my friends!!!! Eric
The 21" prop I had was too much, (4000 rpm, 30 mph, porpoise with much up trim at all) so I dropped to a 17" stainless, and attached a hydrofoil. Tried it out today with the following results:
IMMEDIATELY jumps on plane.
Hits 30 mph in seconds with full down trim.
Slight up trim gives 35 mph and 4400 rpm, but porpoise starts here.
More up trim runs rpm quickly up to 4800, and likely considerably higher, but porpoise beats the crap out of the boat (and me) before I can actually approach the max possible rpm.
Motor can be lowered 2" yet.
No jack plate. Would one help eliminate the porpoise? If so, how big would you think it would need to be?
Will an even lower pitch prop help?
Suggestions (about the boat!!) are welcome. She's totally fishable as is, but I'd like to adjust the wrinkles out of the set-up and make her effecient, solid, and faster.
Thanks, my friends!!!! Eric