6hp prop for a 15' Kaboat

[drivenhard]

I have a Tohatsu 6hp 4 cycle with a 7.9 x 8 prop on my 15' Kaboat. The boat is 60lbs empty and comes up on plane very quickly. It seems like there is more to be had at the top end and I am considering going to a 7.9 x 9 prop. Has anyone had experience with this type of setup?

 

[Sea Rider]

Welcome to Iboats,

Don't do wild guessing prop changes, could ruin your engine. Standard delivered props do a great job on light inflatables as a K boat. What are you trying to accomplish ? Need an induction tach to check wot rpm readings on that 6 HP current prop and go from there selecting best pitch for your particular needs.

Happy Boating

 

[Mi duckdown]

Do not waste money.

 

[steelespike]

While your boat is very light sometimes inflatables are not ideal shape for speed.
Your gps speed lightly loaded would help.I'm guessing speeds about 14 mph.+ or -.

 

[ReelSlow72]

I have a Tohatsu 6hp 4 cycle with a 7.9 x 8 prop on my 15' Kaboat. The boat is 60lbs empty and comes up on plane very quickly. It seems like there is more to be had at the top end and I am considering going to a 7.9 x 9 prop. Has anyone had experience with this type of setup?

You may be trying to drive that Kaboat too hard!!! 14mph in that thing must be a missle!!!

 

[drivenhard]

Thanks for the replies! A friend has an induction tach. I'll give that a try and find out how much the motor is working at speeds.

 

[drivenhard]

The manual says I should see 5-6000 rpm maxed out.

 

[Sea Rider]

Tach that boat/engine combo on flat calm no wind water conditions, inflate that K boat to it's factory stated working pressure, distribute weight evenly on deck, go for a wot spin you alone. Surely will be inside 5-6 K wot rpm parameters. Well top inflated inflatables performs as mini rockets as opposed to underinflated ones, rigidity issues and healthy engine go hand in hand. Post your wot findings..

Happy Boating

 

[drivenhard]

Thanks Sea Rider! The reason I'm checking is it seemed like I hit top speed at 3/4 throttle and any increased rpm didn't have any effect. The boat moves quite well through the water, and I'm very impressed with it so far.

 

[Sea Rider]

To check gained rpm and speed you must check that with an induction tach along a GPS on water conditions as indicated. Throttle to 3/4 check achieved rpm/GPS reading, go wot check same readings. If boat is not correctly top inflated you could be excesively dragging hull on water, that's why feels there's no rpm/speed increase between 3/4 and wot.

If at 3/4 throttle or slight over the carb's pawl roller has stopped at the highest peak on the throttle cam before cam flattens out, just expect a slight rpm & mph increase at wot. Electronic gadgets will provide a accurate veredict.

Once checked with gadgets, check if that engines is correctly height seated, being a 6 HP under powered for that inflatable you must squeeze the max power out of that 6.

Happy Boating

 

[ReelSlow72]

Not sure if these answer what you are looking for my brother but I stumbled across it last night browsing youtube as I myself just ordered a SK470XL Kaboat from BoatsToGo

I think this is the motor you are using no?

[YT] s-y616Sv6uo [/YT]

Can someone help me here darrnit!?!?
http://www.youtube.com/watch?v=s-y616Sv6uo
and http://www.youtube.com/watch?v=JHNbekLZAzg

 

[drivenhard]

Not sure if these answer what you are looking for my brother but I stumbled across it last night browsing youtube as I myself just ordered a SK470XL Kaboat from BoatsToGo

I think this is the motor you are using no?

[YT] s-y616Sv6uo [/YT]

Can someone help me here darrnit!?!?
http://www.youtube.com/watch?v=s-y616Sv6uo
and http://www.youtube.com/watch?v=JHNbekLZAzg

That motor was a Mercury (2 cycle?), I am using a Tahotsu 6hp.

 

[drivenhard]

To check gained rpm and speed you must check that with an induction tach along a GPS on water conditions as indicated. Throttle to 3/4 check achieved rpm/GPS reading, go wot check same readings. If boat is not correctly top inflated you could be excesively dragging hull on water, that's why feels there's no rpm/speed increase between 3/4 and wot.

If at 3/4 throttle or slight over the carb's pawl roller has stopped at the highest peak on the throttle cam before cam flattens out, just expect a slight rpm & mph increase at wot. Electronic gadgets will provide a accurate veredict.

Once checked with gadgets, check if that engines is correctly height seated, being a 6 HP under powered for that inflatable you must squeeze the max power out of that 6.

Happy Boating

I did as directed above. My wife was in the boat during the run. At 5110 rpm I had 10.4 mph on the gps. I don't now what you mean by "correctly height seated". The anti-ventilation plate is well below the boat. I changed the trim angle and did not find much difference in the wot speed. The manual say 5-6000 rpm is the proper range and it looks like I am in the ballpark.

 

[drivenhard]

To check gained rpm and speed you must check that with an induction tach along a GPS on water conditions as indicated. Throttle to 3/4 check achieved rpm/GPS reading, go wot check same readings. If boat is not correctly top inflated you could be excesively dragging hull on water, that's why feels there's no rpm/speed increase between 3/4 and wot.

If at 3/4 throttle or slight over the carb's pawl roller has stopped at the highest peak on the throttle cam before cam flattens out, just expect a slight rpm & mph increase at wot. Electronic gadgets will provide a accurate veredict.

Once checked with gadgets, check if that engines is correctly height seated, being a 6 HP under powered for that inflatable you must squeeze the max power out of that 6.

Happy Boating

I did as directed above. My wife was in the boat during the run. At 5110 rpm I had 10.4 mph on the gps. I don't now what you mean by "correctly height seated". The anti-ventilation plate is well below the boat. I changed the trim angle and did not find much difference in the wot speed. The manual say 5-6000 rpm is the proper range and it looks like I am in the ballpark.

 

[Sea Rider]

Drivenhard,

Having the lower leg seated at its best transom height, is a theme that carrries great controversy between real world practices and plain theory on what's stated on owners manuals, word of mouth, read it somewhere else. Beeing doing this for years and works top on any kind of inflatables provided that all count with a built back solid transom. Check this : http://www.rib.net/forum/f50/abc-sib...nes-58373.html

Follow them to the letter and report your findings. Have a good boating day. Btw, how did you found all about regarding AV plate issues ?

Happy Boating