Speed differance between a Tohatsu 9.8 or 15

[ali'i]

Hi everyone, newbie here, so go easy. I have a 12' , soft bottom inflatable, and I have a chance to get a great deal on a new Tohatsu, but can't decide which one, a 9.8 or a 15, the dry weight of the 9.8 is 81.5 lbs, while the 15 is 114.4 lbs, what I am trying to decide, is does the extra 33lbs of the 15 cancel out the extra hp, or would I still see a noticable difference in top speed over the 9.8. I guess another way of putting, is that if 2 equal boats where to have race, would the 15hp be a little faster or alot, Thank You.

 

[trendsetter240]

Re: Speed differance between a Tohatsu 9.8 or 15

I think there will be a noticeable difference in speed (both accelerating and top speed) between the two. Is the boat rated for 15hp? If it is then I'd go with the 15. If it's not rated for 15 then go with the 9.8.

The only drawback I see would be lugging around that extra 33lbs if you take the motor on and off frequently.

 

[Sea Rider]

Re: Speed differance between a Tohatsu 9.8 or 15

Is it 2 or 4 strokes engine ? If that sib is rated for a 9.9 HP you could place a 15 if it were a 2 strokes, are same size and weight. A 12 footer should handle well a 15 four strokes. A 15 will plane sib much faster, carry more weight with better top speed than a 9.8 HP. You can update for a larger size sib in near future. Just inflate well all air chambers to minimum 3.0 psi with a gauge and will have a nice boating time. Go for it.

Happy Boating

 

[ali'i]

Re: Speed differance between a Tohatsu 9.8 or 15

Is it 2 or 4 strokes engine ? If that sib is rated for a 9.9 HP you could place a 15 if it were a 2 strokes, are same size and weight. A 12 footer should handle well a 15 four strokes. A 15 will plane sib much faster, carry more weight with better top speed than a 9.8 HP. You can update for a larger size sib in near future. Just inflate well all air chambers to minimum 3.0 psi with a gauge and will have a nice boating time. Go for it.

Happy Boating

The 9.8 and 15 Tohatsu are 4 stroke, I am in Canada, and you can't buy new 2 strokes anymore, The boat is a
Z-ray 11, 500, it is rated at 9.9, with maximum engine weight of 110 lbs, but a local marine shop said rule of thumb is its okay to go 10% over that weight, which would be 121 lbs, and since the 2012, 15hp Tohatsu weighs 114.4, I feel I should be okay. right??. And I don't have extra weight from launching wheels either, Also, I have found the identical boat for sale on a website for a supplier in China, "aliexpress.com", and the data on there says maximum hp is 15, so???. I'm sooo confused. I know I could just buy a used 2 stroke 15, which would be lighter, but I like the idea of 5 years of piece of mind with the 5 yr warranty on the Tohatsu's. Tomorrow is judgement day, otherwise I miss out on the great deal, what to do? what to do?...

 

[Sea Rider]

Re: Speed differance between a Tohatsu 9.8 or 15

See it this way :

Tohatsu 9.8 : just for goofing around, heavily loaded, t will bore you faster than you can imagine.
Tohatsu 15 : full fun guaranteed.

Are you worried by engine weight or speed ? We use 10.5" sibs rated for 15 HP with Tohatsu 18 HP. Well inflated and knowing what to do not a single issue with that configuration. You can always throttle less than wot untill the beast has been tamed. Do you have any legal issues placing a bigger engine than it's rated for on tech plate ? If not, go straight for the 15.

Happy Boating

 

[ali'i]

Re: Speed differance between a Tohatsu 9.8 or 15

Are you worried by engine weight or speed ? We use 320 sibs rated for 15 HP with Tohatsu 18 HP. Well inflated and knowing what to do not a simgle issue with that configuration. Personally would go straight for the 15. You can always throttle less than wot untill the beast has been tamed. A pity that there aren't no 4 strokes Tohatsu 9.9 HP, which should weight same as the 15...

Happy Boating

If the boat was an aluminum or fiberglass rated for maximum 9.9hp, 110lb, I wouldn't really be worried about going to a 114.4 lb,15hp, but being that the boat is an inflatabe with the transom basically just bolted to the glued on brackets on the tubes, I just don't know, after all, I am new to inflatables. I am not too worried about the weight, after all, its only over by4.4 lbs, and my theory is if I accelerate slowly, instead of gunning it, then there shouldn't be a problem either, but if anyone knows otherwise, and if it helps, there will never be more than 2 people in the boat, (about 350lbs)plus gas tank, etc, and the boats max load is 1331 lbs.

 

[Sea Rider]

Re: Speed differance between a Tohatsu 9.8 or 15

You only need to :

1-Have that 12 footer well top inflated including keel.
2-Select proper trim hole.
3-Distribute weight accordingly for good ballancing and fast planing.
4-Engine sits at correct transom height.
5-No need to run wot all the time, throttle to 3/4 and once on plane reduce throttle to 1/2 or slight more to maintain sib on plane.

Can assure you that if Tohatsu develops a 4 stroker 9.9 HP will weight exactly same as it's 15 HP older brother. Is the same example as in 2 stroker 9.9/15 HP models. 9.9 are just rectricted models from same 15 HP models.

Happy Boating

 

[trendsetter240]

Re: Speed differance between a Tohatsu 9.8 or 15

If the boat is rated for 9.9 then don't get the 15. Like you said; it's not a fiberglass or aluminum with a solid frame.

The 9.8 will move that boat along nicely and will be safely near the top of the rated HP and weight.

 

[ali'i]

Re: Speed differance between a Tohatsu 9.8 or 15

Thanks to all who have replied. I think I am leaning towards the 9.8, it's lighter and $367 less, plus in Canada, if i went with the 15, i would have to license the boat, no charge for that, but would have to display 3" high, numbers on each side, just doesn't look right on a small inflatable. FYI, the boat I have is identical to the Z-ray 500 being sold in the U.S by Red Star Marine, who have ads on here. But I have one more question for those in the know, with my boat and the Tohatsu 9.8, 4 stroke, on flat water, no headwind, 1 person, (165lbs), can you ballpark my top speed? and to refresh, the boat is 12', soft bottom, aluminum floor, inflatable keel, Many Thanks......

 

[CapeAnn]

Re: Speed differance between a Tohatsu 9.8 or 15

I'd say easy 20 + mph on the 9.8. A guesstimate as I didn't have a GPS with me. I haven't opened up the 15 yet, but I'd say comparable speed.

BTW - moving the 15HP Tohatsu on and off the transom is a back-wrenching affair for one person. I can do it, but ouch after a while. 9.8 is easey peasey. Whenever I park the boat for longer term I always rest the skeg on top of some styrofoam to relieve weight from the transom - lest the glue starts undoing itself.

 

[Sea Rider]

Re: Speed differance between a Tohatsu 9.8 or 15

Before buying a 9.8 try to test one with your 12" sib and see if it will plane with 2, 3 passengers so to know it's passenger weight limitations, if it's ok with 2 and not with 3 you decide. Some sibbers using Tohatsu 9.8 mounted on 360/380 sibs with 3 or more passengers have experiemented planing problems which were solved passing to 15 HP Tohatsu engines. A 4 strokes 9.8 is only 210 CC compared to 350 CC for the 15.

Happy Boating

 

[Ctboaterguy]

Re: Speed differance between a Tohatsu 9.8 or 15

I have an 11' inflatable. With a 1980 8hp mariner 2stroke 2 ppl 13mph gps speed. Same boat 1958 fastwin 18 , 20 mph gps 2 ppl. Gets on plane ALOT faster. Only tried 18 once. Floor&keel wtry again. Boat rated for 15hp.

 

[TOHATSU GURU]

Re: Speed differance between a Tohatsu 9.8 or 15

9.8 22 to 24 mph
15 25 to 28 mph.

However, imagine your car's top speed. Now imagine your car's top speed with 5 fatties in it, going into the wind, up a mountain with a trunk full of dead bodies...Moral of the story is that the variables defy a certain set anything.

 

[Sea Rider]

Just answering a post that disappeared in front of my eyes...

You can't, are different 4 strokes horses. A 9.8 HP is 210 CC and a 15 is 350 CC. The restriction only applies to 2 strokes engines, but ain't a 9.8, its a 9.9 compared to a 15 HP, as both are same 250 CC.

Happy Boating

 

[lemondrop9344]

Is this a current thread?

 

[TOHATSU GURU]

no.

 

[GA_Boater]

Is this a current thread?

No. The post that was answered by Sea Rider was a deleted hijack. SR's post ended up as a cross-post of sorts. Sorry, Sea - Inadvertent consequences of a hijack clean up.