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2iar
02-09-2005, 02:44 PM
I've just got back from the boat show, and am now more confused than when I went :(

I was considering a new motor for my 11 footer. Just a 9.9 as it's only rated to 10. I've currently got a 1990 9.9 Yamaha on the boat that I figure is a bit heavy (that also seemed to be the opinion of a couple of guys I spoke to), as it sits a bit low at the back and needs a foil.

Looking at a Tohatsu, they've got a 9.8 that only weighs in at 26kg (i'd guess mine is closer to 40kg, but haven't checked it). This looked appealing and at a decent price. However, it was pointed out to me that it only displaces 10.3 cu. in. at 169 cc - the same as 8 & 6 hp's in the range. (I'm confused even typing this from the specs, but hope someone else understands it to give me some advice).

Comparing this with, say, a Mariner 9.9, weighing 35Kgm, displaces 16 cu in (262 cc).

So it seems the Mariner is much more powerful, but nearly the same HP rating. If there's such a big difference, why rate boats with HP ratings in the first place.

What's better for my boat - weight and CC's or light and less cc's? Laslty, do small Tohatsu's have a bad rap (seems to depend on which professional you ask)?

Please, somebody, HELP!!!

Mike

Fishin_Dan
02-09-2005, 03:02 PM
Mike, I asked about Tohatsu's on another post, and it seems that not too many people seemed to have them, but nearly everyone was really happy with them. Do a search for Tohatsu in this section.

scuttlebutt
02-09-2005, 03:03 PM
For a little boat like the 11 footer I think the light motor would be a good match. The engine with the greater displacement probably has more torque though this effect is more noticable with heavier boats or loads. If you were going to be loading the boat down with heaps of gear, three or so people then the greater displacement would be more effective.

Greater displacement generally means more torque, meaning you can load it up more and it'll still be able to maintain the bulk of it's speed. Think of a 5litre V8 falcon compared to a 2litre WRX pushing out similar horsepower. The WRX is faster unloaded, but try towing a boat with it.

cheers,

steve

FNQCairns
02-09-2005, 03:29 PM
What scuttlebut said. Try comparing these small capacities with dirt bike engines, the comparison then is obvious to anyone who has riden one- that little cc tohatsu is best left on the shelf ain't no way it will do a rounded job like your current engine and certainly not like the 260cc engine. Possibly another brand might meet half way?
cheers fnq

2iar
02-09-2005, 03:58 PM
Great, 2 different answers already :D

Thanks for clearing that up :D

Seems most of the 9.9's weigh about 35kg, while the Tohatsu 9.8 was only 26. That was what I was after, but I'd prefer to sit a little lower in the bum and get to my destination quicker with the current donk.

I don't really know what they mean, but some guys were telling me that similar motors (like Tohatsu 9.8hp/8hp/6hp) are the same just the smaller ones are "de-tuned". So it looks like everyone else has de-tuned their 15's to 9.9, where as Tohatsu are fully tuned 8/6hp to 9.8 (if that makes sense). That would at least explain the weight difference.

Still seems odd that the hull is rated to a certain HP, but the weight/"power" of the similar HP engines are so different. Ideally, I would be able to use a 35kg 15hp, but the hull's not rated for it, even though it's essentially the same motor as a 9.9. Interstingly 9.9's & 15's cost the same.

I reckon I need some ice for my brain. Thanks for the replies.

Mike

billfisher
02-09-2005, 04:13 PM
I wouldn't worry about the displacement of the Tohatsu. The drop in weight will help performance quite a bit on an 11 footer. I don't think you will notice the drop in torque too much, ie you will still get the same top speed even if the engine has to 'wind out' a little more. I have an 18 hp Tohatsu that weighs only 40kg and it is a very powerful little motor.

krazyfisher
03-09-2005, 07:55 AM
i think the tohatsu 9.8 is the light weight one. they also make a 9.9 which is the same size as the 15hp. i believe yammie 9.9 is also the same as a 15. I would get them to put the tohatsu 9.8 on and go for a run i would think someone would do this for you

semut
03-09-2005, 12:44 PM
Hi every body,
I 'm new member of this chat forum.
I have hydrofield 5.6m fiberglass boat, currently has 100Hp Suzuki motor ( 2 stroke motor) and like to change it with 4 stroke motor, prefered Yamaha (are they good ????) Not sure how much / max Hp motor can I put onto the boat ? Can someone please help me to give some suggestion will be most appreciated.
sign sem

basserman
03-09-2005, 06:27 PM
semut i have a mate with the same size hydro and he has twin honda 50hp (feels underpowered to me but hey he lives in sydney and doesn't do bar work) so not sure if that is a option with you
as for yamaha they would be very close if not the biggest outboard sellers in australia and not too many bad things get said about them
mind you most outboards these days are very good and relabile as long as you look after them

but will give you another thing to think about
the suziki 140hp four stroke is lighter than any 115hp fourstorkes on the market ;)
but you need to find out how many gee gee you can put on the back first and what weight the transome can hold safely