Anyone convert their 4 or 5 hp to a 6 hp? Results?

[fortunate2001]

I have a 5 hp, 2003 Tohatsu 4 stroke, and except when I am by myself or with small kids, it is just not enough to get my 10 foot inflatable (air floor) out of the water. Wondering if putting on the 6 HP carb would indeed get me ~20% more, maybe enough to get two adults planing?

Have visions of cruising along with the family, time to tinker, or look for an 8 hp?

Thanks for relaying your experience-

 

[pvanv]

Re: Anyone convert their 4 or 5 hp to a 6 hp? Results?

Yes, the carb upgrade works very well. We have done dozens of them, with no complaints at all. Of course, the most dramatic increase is when converting a 4 to a 6, as that's a full 50% increase. Still, the 5 can benefit as well, and I'm sure your boat would plane a little easier at 6 hp.

However, I would suggest that even at 6 hp, you may still have too small a powerplant for that boat... it will struggle, and you will notice that struggle more if you load it down. Especially with an air floor/keel (harder to plane than a rigid bottom), if the placard says it's OK, a 9.8 would serve you better. If you are not rated for a 9.8, go for the 8. Same motor, just de-tuned so that it can be used on boats that are not quite rated for 9.8. Most 10-foot inflatables of the type you described are rated for up to 10 hp; Many of them are rated for a lot more.

The rule of thumb is that if you don't have at least 75-80% of rated power, you may be disappointed in the performance of the boat/motor combination.

 

[Sea Rider]

Re: Anyone convert their 4 or 5 hp to a 6 hp? Results?

An air floor needs to be inflated at least to 10 PSI and keel to 3.0 PSI to perform as expected with max engine rated for that sib, if incorrectly inflated will have excesive bottom drag and worst with smaller engine.

Happy Boating

 

[fortunate2001]

Re: Anyone convert their 4 or 5 hp to a 6 hp? Results?

Thanks for the replies. I like best the idea of getting a 9.9 (max rated), but I hesitated because I saw this same zodiac with a honda 4 stroke 9.9 on it and the bow was sticking up in the air due to the weight of the motor. That was ~5-6 years ago, maybe they are lighter now...

I saw a 2-stroke 9.9 used the other day, looked to be in very good shape, but they wanted $1500 for it; seemd a little high, but what do I know. I think it was about 80 lbs. My 5 HP is ~55 lbs. If memory serves me the old 4 stroke honda 9.9.was closer to 100 lbs.

 

[pvanv]

Re: Anyone convert their 4 or 5 hp to a 6 hp? Results?

Right on all counts! The Tohatsu/Nissan 9.8 weighs in at 82 pounds; Lightest motor in its class. The 9.9 (NLA from Tohatsu/Nissan) was well over 100 pounds, as is the Honda. In the US, the only way to get a 2-stroke in that size range would be used.