Outboard Weight

gstraub · Posted: Thu Jan 05, 2023 6:48 am Post subject: Outboard Weight

I am leaning toward re-powering with a 90 HP Tohatsu on our C-22. One thing that I am concerned with is the weight. The Tohatsu is listed as 392 lbs. The Honda BF90 that I am replacing is listed as 365. A new Yamaha is 362 and the Suzuki is 344. The boat manual says optimum transom weight is 375 with motor and batteries and should not exceed 500. With the Honda, when I put an old Johnson 8.8 on there as a temporary kicker, I didn't like the trim, at least when she was sitting in her slip.

The Tohatsu I can get quicker, is less expensive, they seem to have a good reputation, and the dealer is really responsive, which is why I am leaning this way.

Appreciate any thoughts on this.

srbaum · Posted: Thu Jan 05, 2023 8:44 am Post subject:

Take a side by side look at the Honda and the Tohatsu... They are both exactly the same, with different paint and decals and both are made by Honda.
It's interesting how manufacturers work together to sell various product lines, for example all Tohatsu small outboards are relabeled as Mercury, Mariner (Mercury"s overseas product line), Nissan and The last of Evinrude's small 4 strokes.

gstraub · Posted: Thu Jan 05, 2023 8:48 am Post subject:

Actually, the new Tohatsu is not the same as the Honda. They used to be the same engine, but no longer. I even downloaded the manual and took a look and was also verified by the dealer.

srbaum · Posted: Thu Jan 05, 2023 9:04 am Post subject:

You got one on me... I worked on a 90 Tohatsu last year and it was the same as Honda. Guess things have changed and I have not looked at the latest of their offerings.

thataway · Posted: Thu Jan 05, 2023 11:00 am Post subject:

The most recent Tohatsu 90 block is almost 500 CC larger displacement and weight is almost 40 # more than the Honda. Also Tohatsu gives torque curves on their motors--something that up until now was not readily available.

T.R. Bauer · Posted: Tue Jan 10, 2023 12:25 pm Post subject:

Get the one you want. The weights you cited are not that much different. Think about all the twin powered boats out there with multiple batteries and heavy splash well coolers - they're fine and probably right at the 500 pound limit if not a bit over.

T.R. Bauer · Posted: Tue Jan 10, 2023 2:03 pm Post subject:

Bob - I agree it's interesting they published the torque curve. The curves for horsepower and torque always crosses at 5252 rpm - it's a math thing. Anyway, in analyzing the 115 from Tohatsu, it leads me to believe that while it says 115 hp on the sticker, the outboard is probably quite a bit more powerful than that in looking at how high the torque curve is. The same can be said of the 90 hp. One could argue the hp curve just flattens off at 525 rpms, but that isn't generally how that works with SOHC 4 valve engines that breath well. Some old clunky 2 valve pushrod fuel sucking engine with giant displacement? Well yes, but this isn't remotely close to that. It is interesting how they were able to pull off equidistant exhaust tubes on an outboard engine and I bet it makes a big difference in real world performance. Anyway, looks like a pretty cool engine to me. I want two of them....lol....

gstraub · Posted: Tue Jan 10, 2023 4:33 pm Post subject:

I finally decided (today) on the 90 HP Mercury with the Command Thrust option. It comes in at the same weight as the Honda currently on the boat. I really liked the Tohatsu, but I know how my boat sits with the current engine and just did not want the extra weight. The dealer seems really helpful as well, although the Tohatsu dealer was extremely responsive as well.

CPlay · Posted: Wed Jan 11, 2023 11:54 am Post subject:

I think you will be very happy with that decision. I also decided to go with the Mercury 90s (qty 2 on my Tomcat 24) 2 years ago. Mercury is not as light as the Suzuki but it does give you the most displacement at 2.1 L. Mine have been trouble free so far.
-Jeff-

gstraub · Posted: Sat Jan 14, 2023 5:45 am Post subject:

Thanks, Jeff. Can't wait to give the new engine a try!

bobjarrard

The 90 Tohatsu is a detuned 140 HP and the 115 HP is the same. They have the same engine weight. Bob

srbaum · Posted: Sat Jan 14, 2023 5:39 pm Post subject:

Bob,
Looking at the Tohatsu site, the 75 is also the same engine...

thataway · Posted: Sat Jan 14, 2023 11:19 pm Post subject:

It makes me wonder: getting 75 and 140 HP out of the same block! (1.6L). Look at the torque curves at 4000 where many of us are running. Not all that much different. Get up to 5500, then that is the difference between th 75, 90, 115, and 140...

bobjarrard · Posted: Sun Jan 15, 2023 11:05 am Post subject: What do you get?

All else being constant, as you increase horsepower (mainly at the top end of RPM) you lose motor reliability/longevity, likely fuel mileage across the board (but not as linear as you might assume - EFI and engine management help out), the engine may start to want mid-range/higher octane fuel, and your driving style might move to the hole shot and damn the torpedo's end of things.
Before I bought a 75 that is so detuned, I would buy the smaller block just below, especially if I could get some weight savings. But as we see 115's on CD 22's, I would go for the big dog at Tohatsu and change out the cowl graphics, let the insurance issue and hull sticker debate be for another time. Want a nice change? Add an Armstrong to the back, fill in the splash well, add a nice little kicker motor to a cut out in the bracket on one side and a real swim ladder on the other leading to a transom door.
Dream Dream Dream Dreamer who after maybe 15 years of being a BRAT still have yet to pull the trigger on a CD. I have a nice little Gregor 13 on a trailer with a brand new Mercury 8hp that cost me all of $1200. Cheap emotional check insurance. I wore out the first truck I bought to pull the CD I did not buy and bought the exact model and year to replace it, sorta like Cargo Cult, maybe the Tundra will attract a CD into my tipi. See ya. Bob
PS: Just renewing my invitation to any of you to come see us in Boulder City; Mead is still a lot of lake and below the dam the Colorado is just the same as always - only 30 minutes to the Willow Beach launch and we have full hookups here at the house (and a pool if you are a polar bear this time of year).BJ

T.R. Bauer · Posted: Sun Jan 15, 2023 1:57 pm Post subject:

I think it's pretty cool they got 140 hp out of 1.6 liters....and that's only about 100 cubes. There once was a day that everyone thought 1 hp per cube was reasonably safe on a pushrod engine - even if you beat on it hard. However, those days have long pasted us by with improved metallurgy, machining processes, engine management tech/fuel injection/variable valve timing, and overhead cams with 4 valves per cylinder.

I would say that with today's technology, you're not going to push the envelope at all until you introduce turbo and supercharging power adding tech. And even you're probably not by very much as there are lots of 2 liter productions engines are making 300 or even 400 hp these days with turbos and lasting about forever. I honestly wouldn't worry that much about 140 hp from a 1.6 liter overhead cam engine. If there is one weak link, it probably is the lower unit's limit to take the RPMs these things can spin up to, which is why they have rev limiters....