18HP or 20HP Tohatsu?

[5Feezy]

Hi all, I'm a newbie here and was hoping to get a little advice on powering my boat. I'm looking to get a 4 stroke tiller steer for my old 13 foot Boston Whaler and have been leaning towards the 20 HP Tohatsu. It is the most powerful, light 4 stroke for a cheap price. But I have now found a 2003 18 HP Tohatsu for about a thousand dollars cheaper. I'm wondering how much of a performance difference would be felt in my application.

According to the Tohatsu website, the 18 has less displacement than both the 20 and 15 HP models (328cc vs. 351cc). I know that more displacement equals more torque and that is what I need since my boat is on the heavier side. I want to be able to at least plane out with two adults (hopefully three) and maybe pull a ten-year old around on a tube.

I don't want a larger motor because of the weight on an old transom, nor do I want a 2-stroke. Are my goals achievable with the 18 or 20?

Thanks.

 

[pvanv]

Re: 18HP or 20HP Tohatsu?

The 9.9, 15, 18, and 20 are all based on the same block. Similar weight, too. Many parts interchange among this motor family. The 20 will have about 10% more power than the 18 at WOT.

We service quite a few of these, and they are very durable. They are both good choices. The 9.9 and the 18 have been out of production for a couple of years. Tohatsu now offers only the 15 and 20.

If you want new, get the 20. Used, the 18 seems a little overpriced, but it's still a bunch cheaper.

 

[Wee Hooker]

Re: 18HP or 20HP Tohatsu?

IMHO, the 2 Hp is in the weeds and likely transparent on a boat that size & weight. I'd also note that IF you plan to run the boat @ WOT most of the time ( i.e. where you'll see those extra 2 HP), you really should reconsider a bigger motor. Those 13' whalers are heavy!
That said, the decision (IMHO) would be more about buying new or used.
If you buy a new 20, you'll get a zero hours , properly broken in motor that comes with a 5 year warrenty. If you buy a used 18 (or any other size), you save $1K (that's near 35%!) but get some unknowns. It's really a personal call based on your needs and finances.

p.s. If there is any chance of demo'ing either motor, I'd take the time to do it before deciding. It would be a shame to spend near $3k on an outboard only to find it didn't meet your expectations.

 

[TOHATSU GURU]

Re: 18HP or 20HP Tohatsu?

I'm with him I think your under powered with any 20 on that boat. The last one we rigged was with a 40 in a remote. I would suggest at least a 25, regardless of brand, with a 30 being the smallest practical size.

 

[5Feezy]

Re: 18HP or 20HP Tohatsu?

Is the 18 really smaller displacement than the 15 though (328 vs. 351)? I'm more worried about the torque of the motor than its actual horsepower.

 

[TGuy]

Re: 18HP or 20HP Tohatsu?

If you buy a new 20, you'll get a zero hours , properly broken in motor that comes with a 5 year warrenty.

5 year warranty? According to the "news" section on their website www.tohatsu.com, the 5 year warranty promo is only valid on 25hp and above models. For the 20hp and below, their standard 3 year warrant applies. Still a good deal though.

 

[pvanv]

Re: 18HP or 20HP Tohatsu?

This family of motors is a 60mm stroke across the board. They were 59mm bore, until the present "C" series. Now they are 61mm bore, same 60mm stroke.

So the 18B was 59mm bore x 60mm stroke. The 18 hp motor was dropped when the C series came out. Minor displacement difference of 328 cc (old series) versus 251 cc (new series).

So yes, a new 15C/20C is actually slightly more displacement.

The connecting rod angularity is the same for both series, while the mass of the 59mm piston is actually a bit less than the 61mm piston, so I doubt you would notice much low-end torque difference per cc.

FWIW, the 3-cylinder EFI motors (25 and 30 hp) are the same bore x stroke geometry as the old 9.9B/15B/18B, that is, they are 59mm bore x 60mm stroke. Of course they are 3 cylinders...

 

[TOHATSU GURU]

Re: 18HP or 20HP Tohatsu?

"Is the 18 really smaller displacement than the 15 though (328 vs. 351)?"

Yes...The 18 is an older design that has been discontinued.

"I'm more worried about the torque of the motor than its actual horsepower."

Torque is a meaningless term when discussing the power of an outboard as you have a fixed gear ratio...IE. The torque that the engine produces at the power head varies with engine RPM and is governed by that fixed gearing. That's the reason outboards are all rated at WOT with a prop shaft hp rating.

 

[5Feezy]

Re: 18HP or 20HP Tohatsu?

Wow, you guys know your stuff!

 

[Sea Rider]

Re: 18HP or 20HP Tohatsu?

Hi all, I'm a newbie here and was hoping to get a little advice on powering my boat. I'm looking to get a 4 stroke tiller steer for my old 13 foot Boston Whaler and have been leaning towards the 20 HP Tohatsu. It is the most powerful, light 4 stroke for a cheap price. But I have now found a 2003 18 HP Tohatsu for about a thousand dollars cheaper. I'm wondering how much of a performance difference would be felt in my application.

According to the Tohatsu website, the 18 has less displacement than both the 20 and 15 HP models (328cc vs. 351cc). I know that more displacement equals more torque and that is what I need since my boat is on the heavier side. I want to be able to at least plane out with two adults (hopefully three) and maybe pull a ten-year old around on a tube.

I don't want a larger motor because of the weight on an old transom, nor do I want a 2-stroke. Are my goals achievable with the 18 or 20?

Thanks.

That I know there is no 4 strokes 18 HP engine, 2 strokes 18 HP has 294 CC compared to 351 CC for both 15 & 20, 4 strokes models. 2 strokes 18 HP is still in current production for markets where no polution restriction laws are applied. If opting for the 1 grand lesser 18 HP, you could play with pitch to optimize your boating performance. The 18 is a very nice and reliable engine.

Happy Boating

 

[TOHATSU GURU]

Re: 18HP or 20HP Tohatsu?

The 4-stroke 18 almost certainly wouldn't have been imported down your way...No one would want a four-stroke willingly when a lighter 2-stroke was availableWe have emission laws that have done away with most 2-strokes here.

 

[5Feezy]

Re: 18HP or 20HP Tohatsu?

The 18 that I'm looking at is actually a 4 stroke from 2003. I'm in CA and there's hardly anywhere around here that accepts 2 strokes, or I would definately look for more power. I want to keep this boat as simple and light as possible. I'm going to look at that 18 in a couple of days, and if I get it I'll let you all know how it performs.

 

[mickjetblue]

Re: 18HP or 20HP Tohatsu?

I have had the 18 for a few years on a light jon boat.
I have put it through the ropes, including some tube pulling.

So, to answer your question about whether or not an 18 or 20 will achieve
your goals, I would answer "marginally". And because of riding the margin,
a 20 will be marginally better than the 18. I agree with what was said before
about 30 or 40 being right for what you want to do. The 18 is a good motor,
and you can have good times with it. Everything is a compromise.



Big advantage of the 18 or 20 is that you can run either at or near WOT
and use very, very little fuel.

Good luck!

 

[Wee Hooker]

Re: 18HP or 20HP Tohatsu?

I stand corrected on the warrenty period. I thought it was for a broader range. 9 it would be helpful if Tohatsu had advertized teh warrenty upgrade on their main page!). Still, all teh more arguement to go to the 25 or 30 IMHO.
Guess the point is OBE now anyway.