length vs width

[Nason]

If switching the motor from a 40 to a 60 is that easy then yeah it would make some real difference. There is a catch or 2 tho, That doesn't automatically mean your going to gain way more RPM's or speed, more likely acceleration. If you have a rev limiter on it then maybe only acceleration [unless you defeat it] What you will need is the right prop.. all other things being good [?] that will be what brings it together. Good Luck, careful at speed.

The rev limiter is gonna come off once I get the tach installed.

[JohnsonM50]

The rev limiter is gonna come off once I get the tach installed.

Cool, think 'prop'

[Yellowjacket]

Both boats had 40hp merc 2 stroke 3 cycl. Boat # 1 with wider pad ran 51.5 on gps all day long. Boat # 2 ran w/ smaller pad ran 50.3 all day long. Give or take a couple of points. Same motors and props w/ same pitch and dia. The only difference now is that I have a long shaft and its jacked up like a short shaft, which is what they had short shaft motors.

Something doesn't quite compute. They were using the same motor and were going 6 or more mph faster than you are? Sounds like you don't have the right prop or something else in your setup is different. You need to figure out why you aren't making as much speed as they were with the same power. If your prop is in the right place relative to the bottom then something else is wrong, most likely the prop isn't the same. If the prop is the only difference I wouldn't bother trying to figure it out, just derestrict your motor and work on tuing a new prop to the bigger power.

The faster you go the less lift you want. If you add 50% more power (de-restrict your 40 to make it a 60), you are going to be going a good bit faster, and you probably don't want the greater lift. For the tweaked motor the narrower pad is probably what you want, and you will need a new prop with more pitch. With the correct prop you should be in the mid to high 50's if you have 60 hp.

[Nason]

Something doesn't quite compute. They were using the same motor and were going 6 or more mph faster than you are? Sounds like you don't have the right prop or something else in your setup is different. You need to figure out why you aren't making as much speed as they were with the same power. If your prop is in the right place relative to the bottom then something else is wrong, most likely the prop isn't the same. If the prop is the only difference I wouldn't bother trying to figure it out, just derestrict your motor and work on tuing a new prop to the bigger power.

The faster you go the less lift you want. If you add 50% more power (de-restrict your 40 to make it a 60), you are going to be going a good bit faster, and you probably don't want the greater lift. For the tweaked motor the narrower pad is probably what you want, and you will need a new prop with more pitch. With the correct prop you should be in the mid to high 50's if you have 60 hp.

All motors that were on these boats were 40 hp merc 2 stroke 3 cycl The 2 motors did not have power trim and were short shafts.They would take off with the motor all the way down then once they were running full throttle, they would quickly twist the throttle down, move the hydraulic assist ram lever. let the water pressure lift the motor , lock it down then gun the motor full throttle.The boat would go crazy for about 15 good bounces then on the pad and off they went.Those bayou boys are good at doing that task. I have a long shaft but I jacked up my motor to same hight as where the short shaft motors were and I have power trim. To go with the 60 carbs, what do I have to do ? Just put on the carb , reed stops and cut the tunner or relace with 60 tuner or do I have to advance the timing? Any porting to head or block needed?

Thanks for all the help from everyone.

[JohnsonM50]

All motors that were on these boats were 40 hp merc 2 stroke 3 cycl The 2 motors did not have power trim and were short shafts.They would take off with the motor all the way down then once they were running full throttle, they would quickly twist the throttle down, move the hydraulic assist ram lever. let the water pressure lift the motor , lock it down then gun the motor full throttle.The boat would go crazy for about 15 good bounces then on the pad and off they went.Those bayou boys are good at doing that task. I have a long shaft but I jacked up my motor to same hight as where the short shaft motors were and I have power trim. To go with the 60 carbs, what do I have to do ? Just put on the carb , reed stops and cut the tunner or relace with 60 tuner or do I have to advance the timing? Any porting to head or block needed?

Thanks for all the help from everyone.

Must have all year to perfect that.. pretty wild

[Nason]

Must have all year to perfect that.. pretty wild

You would have to be in the boat to actually see how they do the task, its wild but it works for them. They even do it the same way with a 60 4 stroke. I tried several times but always almost landing on the bank, thats why I have power trim.

[Jimboat]

It depends a lot on the size of motor and the weight of the whole rig.

For every weight, CG location and speed, there is a correct pad width. More than that or less than that and you are slower. More width creates more lift, so if you are heavier, you want the wider pad. If you have more power and are going faster, a narrower pad width is what you want. So it's a matter of matching the power you have with the weight and CG, and how fast you are planning to go.

Agree completely with Yellowjacket. A pad can really make a vee hull fly. Each pad should be designed particularly for the hull, power, setup and expected use (speed), however. If not enough pad, the hull can actually be slower, since the vee surfaces will be carrying more load than necessary. Too much pad and handling can be unpredicable, and lift possibly inefficient. Good thing is, that the ideal sizing for a pad can be calculated for any vee hull design.

[Nason]

Agree completely with Yellowjacket. A pad van really make a vee hull fly. Each pad should be designed particularly for the hull, power, setup and expected use (speed), however. If not enough pad, the hull can actually be slower, since the vee surfaces will be carrying more load than necessary. Too much pad and handling can be unpredicable, and lift possibly inefficient.

let say reaching for 55 to 60 mph, which boat would be better #1= 13.5' and 16" pad or boat #2 =14' and 14" pad ?

[Jimboat]

Nason - sorry to avoid the 'quick' answer...to make performance assessment of your 2 boats, we'd need details of each design, and power/weights for each setup, and would then do a dynamic performance analysis of each hull. Send me a quick email if you'd like to pursue more.

[Nason]

Thanks for the help, tomorrow I will take measurements and pictures. How do I post pictures on this forum?