tub003
11-23-2003, 05:01 PM
Hi! Scream And Fly Guys!
I Race A small runabout boat with a 8hp engine. I would like to know how to get more horsepower out of it. If I change the carb to 18mm and increase jet .010 and advance the timing 10 degrees I get 2 mph more. The bore size is 54mm the stroke is 46mm the carb size is 15mm with a .041 jet. The exhaust duration is 140 degrees the transfer and booster ports are 110 degrees. I do not know what the intake duration is yet.The squish is .108in and the tuner length is 260mm long with the small end being 21mm and the big end 29mm. The boat runs at 5800rpm at 36mph.
EXHAUST PORTS. How much could I raise them and should I widen them. What shape should they be and at what angle entering the cyl.
TRANSFER AND BOOSTER PORTS. Leave alone or modify, what shape or angle entering the cyl, or should I just raise the booster port.
PISTON. Shave off top of crown if I cannot go any higher in block with ports. Will .020-.040 help with port duration or how much is to much before piston becomes to weak. Should piston to wall clearance be more than stock.
HEAD. How much squish clearance and squish width. The stock gasket is .052 thick. Can I deck the block and how much can the piston stick out of block. Should I make the chamber smaller and what shape.
Carb. How big can I go.
TUNER. Will all these changes be no good without changing the tuner. Should I just shorten it or change the shape.
I WANT TO KICK SOME BUTT.
I Race A small runabout boat with a 8hp engine. I would like to know how to get more horsepower out of it. If I change the carb to 18mm and increase jet .010 and advance the timing 10 degrees I get 2 mph more. The bore size is 54mm the stroke is 46mm the carb size is 15mm with a .041 jet. The exhaust duration is 140 degrees the transfer and booster ports are 110 degrees. I do not know what the intake duration is yet.The squish is .108in and the tuner length is 260mm long with the small end being 21mm and the big end 29mm. The boat runs at 5800rpm at 36mph.
EXHAUST PORTS. How much could I raise them and should I widen them. What shape should they be and at what angle entering the cyl.
TRANSFER AND BOOSTER PORTS. Leave alone or modify, what shape or angle entering the cyl, or should I just raise the booster port.
PISTON. Shave off top of crown if I cannot go any higher in block with ports. Will .020-.040 help with port duration or how much is to much before piston becomes to weak. Should piston to wall clearance be more than stock.
HEAD. How much squish clearance and squish width. The stock gasket is .052 thick. Can I deck the block and how much can the piston stick out of block. Should I make the chamber smaller and what shape.
Carb. How big can I go.
TUNER. Will all these changes be no good without changing the tuner. Should I just shorten it or change the shape.
I WANT TO KICK SOME BUTT.