3.5 hp on inflatable (on plane?)

[lancelot9898]

Has anyone been able to plane an inflatable with a 3.5 hp(4 stroke) outboard? I know it's possible with a portabote, but wonder about an inflatable. The inflatable I'm considering is a 68 lb Zodiac ( 8'10") with a high pressure floor. How much weight do I need to lose? currently at 200 lbs.

[Colin A]

I have seen it done with a wood floor inflatable (about 8'6") and a 100 lb teenager sitting in the bow with a tiller extension. Other then that it's possible, but the floor would have to be up to full pressure the motor set just right and weight moved just right even then a lot of other variable's may prevent it.

[a64pilot]

I was thinking I have an about 90 lb eighteen yr old Daughter that I bet could, but not any "normal" American

I used to tow her on a "flying tube" behind our CC and had to be real careful, cause she could get altitude if I let her

[hobopacket]

Doubt it would plane in anything less than perfect situations. Probably need to either be ok with not planing or get some more horses.

[jenders]

I have a 8-foot Achilles, and a 5-horse, 4-stroke Tohatsu. I can plane if I'm alone, (I weigh about 185 lbs.), but not with my partner or any additional weight in the dinghy such as gear etc. If I had it to do over again, I'd move up to a 6 horse, or get a 10-foot dinghy and even a bigger motor.

[CHBKAI]

I have a 9 ft something inflatable with a 3.5 2006 Merc. At 225 pounds plus gear I just sit centre on the bench and go a little forward and I will plane after about 30 -45 seconds every time.give a try and full throttle

[watevaworx]

I have a 3.3 hp 2 stroke on a 3.1 m inflatable floor and it plans pretty easily. The killer for you will be the weight of the 4 stroke engine. You might get it to work but you will need to keep the weight forward

[Caliber40]

Why try? Only under best conditions will you accomplish this. Buy a 10 or 15 HP 2 stroke and be done with it!

[CHBKAI]

I have a 5 hp Merc and feel for the size of the boat it is almost to much power .
And yes you are right--you do have to keep the weight forward---weight difference between 2 and 4 stroke is minimal--and who cares about the extra couple pounds ---for me it works great

[hamburking]

My daughter could do it easily. She's about 135 pounds. Dinghy is an Avon Rover with inflatable floor and a 4hp yamaha 4 stroke. Keep the boat light. She loved going fast in that thing, boy did it fly. Really pissed me off cause I was stuck going slow.

[TheThunderbird]

I dream surfing with a 100# young girl...

Mercury 4-5-6HP are basically the same thing, with different carburetor trimming.
The same should apply to other brands.

Just consider that...

[Mike OReilly]

As mentioned by the OP, my 3.5 hp (4-stroke) easily planes our 10’ portabote with one person and gear. She will plane with two adults (me:220#, spouse: 140#) but only in perfect conditions. The 3.5 is light and manageable without crane or tackle. It’s why we chose it.

I think the reason the bote planes so easily is due to lightness and hull shape. I’ve never owned a high pressure floor inflatable, but my sense is a 3.5 hp will be unlikely to plane such a boat very easily. I’d suggest going a bit bigger, or being content to going slow … nothing wrong with that option.

[Tayana42]

I have a 3.5 Tohatsu on an air floor 8.5' dinghy. It'll plane with just me or me and my dog. Not so with a second person or groceries.

[lancelot9898]

Thanks for all the input. The reason for going with the 3.5 rather than the 4,5 or 6 hp is the weight. I want to be able to lift the motor from the sailboat rail down to the dinghy without the use of a crane. If I could buy a 2 stroke 5 or 6 hp then it might be doable, but don't think I could buy new here in the US. Good to hear that the Tohatsu 4 stroke can plane, since it does have a plastic prop and the only outboard with an AL prop is the Mercury. I was thinking that the metal prop might be a little better bringing it up on plane, plus there are two different pitches that can be put on the merc. Also the longer the dinghy the easier it might be to plane as long as I don't get too extreme. Good to hear that I don't need to get down to 100 pounds.

[Paul L]

Can plane and will plane are different. In perfect conditions, no wind, no chop, no dirt on the bottom, tuned outboard with cleanest fuel, minimal gear, new engine - it might plane. But it isn't going to plane when you have a long trip back to the boat against the wind with an ugly chop or with load of groceries or when a bit of slime has grown on the or ......