I Need more power for my 9'6 inflatable

[ranchboat]

I recently sold my 9.9 hp honda motor that was 25 yrs old and tired. I have a new 9'6 inflatable w/ an inflatable hull. My buddies and me primarily use the boat through the surf line (beach launching) and need to be able to accelerate quickly to punch through set waves if they come. Once out, we have a long distance to travel - 5-10 miles before we reach our destination. My question is, my boat is rated for max 9.9 hp and I want to know if a 15hp is too much. I will likely never be out on the boat by myself, and with my old honda 9.9, I could only take one other person since any more people would cause the boat to max out at 3 miles an hour. It would be nice to go out with 3 people once in a while. Will overpowering this inflatable cause problems with my transom or make the boat too squirrly at higher speeds?

 

[dlindeblad]

Re: I Need more power for my 9'6 inflatable

IMHO going up 5 ish more HP will not be a problem. It is a 2 cycle, more than likely, and the extra weight should not cause transom torsion or cause you to flip the boat.

 

[Drowned Rat]

Re: I Need more power for my 9'6 inflatable

All bets are off when you're trying to punch an inflatable through surf. Nobody can tell you it will or won't flip. 15hp motors are typically the same size and weight as 9.9hp motors, the only issue is torque and speed. As long as you know what you're doing and how to handle it.... have at it.

I'd do the same thing.

 

[ranchboat]

Re: I Need more power for my 9'6 inflatable

All bets are off when you're trying to punch an inflatable through surf. Nobody can tell you it will or won't flip. 15hp motors are typically the same size and weight as 9.9hp motors, the only issue is torque and speed. As long as you know what you're doing and how to handle it.... have at it.





-- Thanks for the info to both posts... I live in CA and I can't seem to find a 2 stroke that's new due to the 2006 regulations. Tohatsu makes a 15hp 4 stroke that is 115lbs and the 9.8hp that is 81lbs. Do you think the additional 25lbs will cause any problems with the transom or am I good to go in your opinion - the hull is rated for max 10hp. I can handle it pretty well in the ocean, but usually the only time I've had problems in the past is not being able to outrun a wave coming in or going out through the surf. You've got to be able to punch it to get out quickly before you get caught and the waves we're trying to get past can be 5-10' on the face, so getting caught can cause problems. So bogging has been my main problem in the past and more power sure would be nice. Thanks for your help!

 

[TOHATSU GURU]

Re: I Need more power for my 9'6 inflatable

Ask yourself the following question.

Does California have a law about exceeding the recommended hp?

If it does you are subject to being charged with reckless operation of a motor vessel if you are stopped for any reason. If it does not, you only have to worry about insurance liability and being held responsible for any accident, whether or not you were actually at fault.

 

[Sea Rider]

Re: I Need more power for my 9'6 inflatable

If you still wanting to break the law , inflate well all sib compartments to it's recommended working pressure, that is 3.5 PSI for tubes and 10 PSI for air floor, get a pressure gauge if you don't have one.

Happy Boating

 

[jaymasta]

Re: I Need more power for my 9'6 inflatable

I recently sold my 9.9 hp honda motor that was 25 yrs old and tired. I have a new 9'6 inflatable w/ an inflatable hull. My buddies and me primarily use the boat through the surf line (beach launching) and need to be able to accelerate quickly to punch through set waves if they come. Once out, we have a long distance to travel - 5-10 miles before we reach our destination. My question is, my boat is rated for max 9.9 hp and I want to know if a 15hp is too much. I will likely never be out on the boat by myself, and with my old honda 9.9, I could only take one other person since any more people would cause the boat to max out at 3 miles an hour. It would be nice to go out with 3 people once in a while. Will overpowering this inflatable cause problems with my transom or make the boat too squirrly at higher speeds?

It sounds to me like your old engine was VERY tired and worn. A 9.9hp should have no problem moving 3 people in a 10foot inflatable unless they are all very Large people in which case I don't think you'd fit anyways. I have been out quite a few times in a 10ft inflatable with a newer 8hp yamaha motor and the thing goes pretty good with 2 big guys in it around 220lbs each. I would think a newer 9.9hp in good shape would have no problem with your boat. If the waves are your main concern you could always decrease the pitch of the prop a little to get you moving along a little quicker.

 

[Jdeagro]

Re: I Need more power for my 9'6 inflatable

Ranchboat;

Your answer is not more HP it is more stern lift. In fact going from 9.9 to 15 HP is not going to give you the extra 5 HP you think. You want the HP when you are attempting to plane, and at that point the engine is only turning about 2,000 RPMs. The Max HP is measured at the peak of the RPM curve which is about 5500 RPMs. At 2000 RPMs you will realize less than 2 HP more.

The reason the boat does not want to plane with the extra weight is that the bow angle is high (creating a hill to climb) and the HP to weight ratio, and weight per Sq.Ft. of hull surface is very high. In other words the foot print of the boat is small, and the HP (thrust) is used up trying to climb instead of moving forward.

Let's level out the hill by keeping the stern up so the boat accelerates more level.

There is another post on this forum and this is the link. Read my true story as to why I invented Smart Tabs.
http://forums.iboats.com/showthread.php?t=314232

 

[ranchboat]

Re: I Need more power for my 9'6 inflatable

Thanks everyone for your input. I think a 9.9 hp will do. I live in CA and new 2 strokes either 9.9 or 15 hp don't exist anymore. Gotta buy a 4 stroke and bumping up to a 15 adds 35lbs to the weight of the motor. I do have a hydrofoil that I put on my last motor in its dying days and it would plane fine with just me in the boat. But once I put a buddy in, the thing wouldn't get out of the hole. Took the motor to a local mechanic and he said I needed a rebuilt carb - all gummed up and losing power at max rpms. I've dumped 900 buck into that motor over the course of 7 years, and I thought it was time to upgrade. It seems from all your answers that a 9.9 will have more than enough power to get me up and going. Typically, I launch solo from the beach, so I'm sure it will have enough zip to get out quickly. Thanks again and any other input is appreciated!