5hp vs 6hp Tohatsu, what's the difference?

[dmede]

I have been looking at the 5hp and 6hp Tohatsu outboards for my 14’ skiff. I need to finish up the transom so I want the motor on hand to be sure of fit, but I’m confused about the HP designation on these Tohatsu’s.

Both the 5 & 6 are single piston 123cc motors, same bore & stroke. The only real difference is the RPM range. 4500-5000 rpm for the 5hp, and 5500 – 6000 rpm for the 6hp. So, what does that rpm difference mean in terms of performance on a 300# flat bottom skiff? Is there any advantage to a lower rpm range or a higher rpm range?

dave

http://www.onlineoutboards.com/5hp_tohatsu_outboard_motor.html

http://www.onlineoutboards.com/6hp_tohatsu_outboard_motor.html

[Kaa]

I have a nasty suspicion that both outboards are exactly the same, only the 5hp has an RPM limiter set at 5000 because some marketing weenie decided there's a need for an exactly 5hp engine :-)

Kaa

[dmede]

I have a nasty suspicion that both outboards are exactly the same, only the 5hp has an RPM limiter set at 5000 because some marketing weenie decided there's a need for an exactly 5hp engine :-)

Kaa

Thats what it looks like to me. The question is, does a lower RPM range really amount to lower HP? Will I notice in my not so high performance boat?

And can it be tweaked to make it a 6hp?

BTW, the 4hp is also the same motor but with an internal tank added and a RPM range of 4500-5500???

[dmede]

I emailed a dealer about it. Here's what they said:

Hi David,

RPM's can be modified via purchasing a new carburetor which is generally
most costly than the price difference up front, also, the 5hp and 6hp
utilize a different propeller which provides additional thrust with higher
RPM range. There really is a power difference between all three.

Makes sense I guess. It's only $150 difference, but every little bit counts.

[Kaa]

Yeah, I was about to say that picking the right prop is likely to be more important than that one hp at high revs...

Kaa

[J P]

I've had a Nissan 6hp for a few years. Same machine as the Tohatsu is my understanding. The dealer I bought it from, also a mechanic, explained the difference in the 5 and 6hp. He said that they are basicaly the same engine but they tweaked the 'porting' to get the higher RPM's and HP rating for the 6.

It's been a good reliable and quiet engine for us. We use it to push a 2500lb sail boat when needed. Our biggest challenge with maintenance is how LITTLE fuel we use. We use so little it's hard to keep it fresh. I use fuel stabilizer and try to be careful about keeping clean filters and the carb drained when shut down. The only problem I've had was last year when I test ran it in a barrel early in the spring and didn't run the carb dry. We didn't take the boat out for another month and the carb jets (very small) gummed up. Now I keep some carb cleaner handy. It came with a 3 gallon remote fuel tank but I'm thinking of getting a smaller one.

[boylesboats]

The different? Is cost..

[Bob Cleek]

Lower HP, lower RPM's, bigger prop = little or no difference in performance on a boat like yours and much better fuel economy.

[Thorne]

For me the biggest issue with outboards is the weight. Trailering boats with outboards involves hoisting, heaving, slinging, lifting and nearly juggling the damn motor.

I used a 6hp longshaft Johnson Sailmaster for years, and it pushed my 2000lb+ San Juan 21 at hull speed, and would plane various inflatables with one person.

How does the Tohatsu compare to other similar or slightly smaller motors in weight? I see that it is rated at 55lbs, although I imagine it weighs more in actual use.

Even though it is 4-stroke and air-cooled, the 2hp Honda sure has a lot going for it at 27 lbs (without fuel or oil)...

[calvin]

Is your skiff a planning model? If so go for more power..if not 5 should be ok!

[Tom Robb]

All things being equal, more rpm=more HP. Torque is a different problem.
The 5 will probably live longer than the 6 - less stress on everything. How much longer only their engineers know for sure. Is there a license (tax) needed for the motor? The 5 may well be cheaper there too, which would account for its existance. 9.5 hp engines are basically the same as 15hp but they make 9.5s for lakes where 9.5 is the upper limit permitted which accounts for their existance.
Interesting world we live in.

[dmede]

For me the biggest issue with outboards is the weight. Trailering boats with outboards involves hoisting, heaving, slinging, lifting and nearly juggling the damn motor.

I used a 6hp longshaft Johnson Sailmaster for years, and it pushed my 2000lb+ San Juan 21 at hull speed, and would plane various inflatables with one person.

How does the Tohatsu compare to other similar or slightly smaller motors in weight? I see that it is rated at 55lbs, although I imagine it weighs more in actual use.

Even though it is 4-stroke and air-cooled, the 2hp Honda sure has a lot going for it at 27 lbs (without fuel or oil)...

Weight is my issue as well, which is why I liked the Tohatsu. In the plans Atkin specs a max of about 50 lbs for the motor and 6hp for the power. Tohatsu is the only one who makes a 6hp in that weight range. All the others are based on their next larger block size and usually 80# or more.

But this may all be a moot point as they say since my whole department was just let go this afternoon anyway! :eek: New outboard has suddenly become very unimportant to me.

Thanks for the info guys.

[J P]

Well, that's a bummer.

Yes, I think our 6hp is right around 50lb.

[Thorne]

Sorry to hear about the layoffs -- we are in the middle of them here, too.

http://sfbay.craigslist.org/sby/boa/664870888.html

http://sfbay.craigslist.org/eby/boa/669564268.html

http://sfbay.craigslist.org/nby/boa/663832393.html

But you'll have more time for boatbuilding, right?

;0 )

[Tom Robb]

Bummer, man.
Crap!

[dmede]

thanks guys. the good news I didn't pull the trigger on a new motor before hearing this (and I was very close). so for now that boat will just have to be armstrong propelled. maybe once I see what's happening I'll decide to go after a compromise like some of the ones Throne listed. $250 to get on the water sounds fine right about now ;)

[ssor]

life expectancy. A motor run at 6 hp or at 4 hp will wear out at very different rates.. The 123 cc engine run at 4 hp will probably last forever but push that little darling up by fifty per cent and you could kill it in five years.

[The Bigfella]

Sorry to hear about the layoffs. Good luck.

[py]

Hey, more time for sailing, cool!! Seriously, sorry about the work situation. Hope it works out. You guys really doing a recession over there?

[The Bigfella]

They haven't had one quarter of negative growth yet - let alone the two needed for a recession. Hopefully, they won't either.

I've got a 3.5 Tohatsu. The 2.5 is also the same, and again, I assume its just the revs that vary?

[Paul Fitzgerald]

I have a 3.3 Merc, same as 3.5 Tohatsu.
IIRC the 2.5 is the 3.5 engine with a restrictor plate between the carby and the cylinder.
The 5hp 2 stroke Tohatsu is the best outboard I have ever used. I have had two over the years, never had an issue, always pulled reliably in difficult situations.

[epoxyboy]

And Evinrude does the same 2.3 and 3.5 are the exzact same motor. Buy the bigger carb mainjet and hey presto you 2.3 is a 3.5!
I think its all about letting in enough gas to run the higher revs/more power.

Pete