26M w/ 90 HP

[Terry]

I have a Tohatsu TLDi 90 on my 2006 . I am very happy with the motor and do not regret the extra horsepower. It's very reliable and economical. Definitely the right choice back in 2005 when I purchased the boat. If I had to do it over again I would still go with the 90, but I would look at some of the recent four strokes that are now available.

Brian,
would you consider a 115 tldi? Or do you think it is not necessary.
I am considering switching from a 4 stroke Suzuki 70 (1.300cc) to a 2 stroke TOHATSU Tldi 90. I have a 2004 Mac and I need just a little more power to feel happy.
However, there is a saying, 'No replacement for displacement' that makes me wonder if the Tldi 90 would be the sufficient step up (?) or whether I should go up to a Tldi 115???!!!!

I look forward to your input

Octaman

'No replacement for displacement'
Does this still hold the same value it did way back when? It seems nowadays modern technology is squeezing a lot more HP from smaller displacement engines with turbo charging and other fandangled processes. Some of the newer engines they are putting in cars these days have twice the HP and half the displacement of the old day engines.

[jschrade]

Keep in mind your range requirements as bigger engines eat more fuel ... period.

We motored from Pass-A-Grille to Dunedin Municipal Marina which is a tad over 27 miles going through many "minimum wake" and cruising around 13.5 knots outside of these. I used just about all of a 6 gallon tank.

Also consider where you are as it can be rather difficult to find gas on-the-water and being able to carry on 6 gallon tanks is really handy and cheaper. Given the purpose of getting a bigger engine is to go fast, I would suspect that you would be best to install the 12 gallon tanks or carry 4 6 gallon tanks and be prepared to change them!

Gas is expensive and one of the reasons I have a sailboat or I mean a motorboat ...

Jim

[raycarlson]

the reason a 2 stroke will out perform a 4 stroke of a larger size is a 2 stroke fires all pistons on every 360 degree rotation of the crank shaft a 4stroke fires all pistons only evey 720 degrees of rotation because of the 4 strokes or 180 degree rotations intake-compression-fire-exhaust. the 2 stroke combines these by using ports or holes in the side of the cylinder wall instead of valves in the cylinder head.people will say 4strokes are torquey'r but this is true only at idle to just off idle speeds.2strokes are less efficient with the use of fuel due to combining strokes as you have exhaust and intake occuring at the same time so fuel is not totally burned as it would be in a four stroke.however with the new generation of direct-injected computer controlled 2 strokes the efficency gap has narrowed substancially.i would say the no replacement for displacement is refering to your tow vehicle.don't expect that 3 litre v-6 to pull your 26 over the mountain like the 5 litre v-8 would. on a equal displacement side by side test the 2 stroke will almost always out power an equal size 4 stroke motor.

[Octaman]

Some very interesting postings indeed!

Brian - interesting to hear that you would suggest the 115hp considering you have the already powerful 90.
My concern with the 90 is that it is slightly under 1.300cc. Whereas the 115 is close to 1.800cc. This is where I see the real difference in torque being generated.

Terry - you are absolutely right, but, . . . I have yet to see an outboard with a turbo charger. And until that happens I guess displacement in outboards is the ultimate criterion for torque

jschrade - range is definitely a concern to be counted in the equation. I guess it all depends on how one uses their boat.

ray - I agree, for equal displacement the 2-stroke will outpower the 4-stroke. So, I guess we should all go for 2-strokes on the Macs if speed and performance is the priority.

Now the question in my case woud be, Is the 2-stroke 90hp TLDI a sufficient upgrade from the 4-stroke Suzuki DF70 (1.300cc) or should one go straight to the 2-stroke 115 TLDI as Brian suggests???

Or will a Mac owner always feel the need for a little extra power regardless of the engine (assuming it is 70hp or more) simply because it is probably human nature to keep on wanting a bit more

Thank you all for your invaluable input

Octaman

[Bobby T.-26X #4767]

Now the question in my case woud be, Is the 2-stroke 90hp TLDI a sufficient upgrade from the 4-stroke Suzuki DF70 (1.300cc) or should one go straight to the 2-stroke 115 TLDI as Brian suggests???
Octaman

the TLDI 90 is 75# lighter (and narrower for ez entry from the rear) than the Suzi DF70.
that weight difference, plus the fact that the 90 puts out significantly more torque than the Suzi DF70, and you will definitely notice a difference.

for most uses, you will NOT be able to motor past 20mph (both safely and comfortably due to condition of seas).
so...no need to go to the higher horsepower.

BTW...if i was to re-power today, i would considered the new Honda 90-Vtec.

Bob T.
"DāBob"
'02X w/ '04 90-TLDI (14" x 11 pitch)
Dinghy Motor: '06 2.5-Suzuki

[vkmaynard]

the reason a 2 stroke will out perform a 4 stroke of a larger size is ... on a equal displacement side by side test the 2 stroke will almost always out power an equal size 4 stroke motor.

Where are the links to these valid tests on the exact same boat(s)/weight/gas/conditions with the correct propeller?

The wrong propeller selection alone will loose 5 MPH.

Victor

[elvatoli]

I was offered by the local Tohatsu dealer the 2 stroke 50hp for $5800
He also sells the new 75hp for $7400 with everything installed. Now I only have the Tohatsu 9.8 with manual lift.
He says that there is no reason to install the 75 hp, because on the Tohatsus, the 50 hp performs as a 70hp, and the 75hp performs like a 90hp, and I cant get more speed above the 50hp because the hull speed limitations.
He also is a dealer for Yamaha and Honda, and says that he fully recommends the Tohatsus over the Yamahas and Hondas.

Hector
Port Isabel, TX

[Catigale]

He says that there is no reason to install the 75 hp, because on the Tohatsus, the 50 hp performs as a 70hp, and the 75hp performs like a 90hp, and I cant get more speed above the 50hp because the hull speed limitations.

Uh oh...I think he had better go back to school...

[beene]

I was offered by the local Tohatsu dealer the 2 stroke 50hp for $5800
He also sells the new 75hp for $7400 with everything installed. Now I only have the Tohatsu 9.8 with manual lift.
He says that there is no reason to install the 75 hp, because on the Tohatsus, the 50 hp performs as a 70hp, and the 75hp performs like a 90hp, and I cant get more speed above the 50hp because the hull speed limitations.
He also is a dealer for Yamaha and Honda, and says that he fully recommends the Tohatsus over the Yamahas and Hondas.

Hector
Port Isabel, TX

He is leading you down the garden path my friend

Does not know what he is talking about

[jschrade]

If he said diminishing returns as you add horsepower beyond 50, i would go for that as being pretty accurate. The are counter costs such as fuel consumption and requirements, extra weight that creates more drag that also increases as the weight of the motor and fuel increase (not mention cost). If you watch these threads, you will see that there is not a dramatic boost in performance for adding significantly more HP. But some will spend a fortune on sails for a knot. It's a disease that we all have to some degree

Where each of us falls on that curve is going to vary just like the great variance in the same model of boat - no two are the same.

I suppose one could mount twin 115's and not sink the boat and boy would it go fast - for a little bit! Yah, I hear the mumblings that you could easily modify the rear berth into a gasoline tank - and so you could.


Jim

[Octaman]

for most uses, you will NOT be able to motor past 20mph (both safely and comfortably due to condition of seas).
so...no need to go to the higher horsepower.

Very good point and for this reason I have kept my Suzy 70 4-stroke for six years and have been very happy with it overall.
I would say 85 to 90% of the time you are sufficiently covered with the Suzy 70 and an upgrade is only for the sake of satisfying the remaining 10 to 15% of the time (or part of it)

However, given the calm waters, you also need the extra power when you have more people (weight) on board and need to go as fast (not necessarily faster) as when you are lightly loaded, without sacrificing engine revs.
As other have said in previous threads, the solution can also be to carry two props with one step difference in pitch and switch props prior to launching accordingly. With a significantly bigger motor, you forget all that!

BTW...if i was to re-power today, i would considered the new Honda 90-Vtec.

Wow, interesting to hear - After what has been said I am inclined to lean towards 2-stroke.
However, when comparing the Honda 90-Vtec (which I think is a great motor) with the new Suzuki DF90A, they are almost the same in cc but Honda has a single overhead cam with 16 valves, whereas the Suziki has double overhead cams with 16 valves, therefore more moving parts but perhaps a more power-oriented engine?. Now, which road do we go down ?

The wrong propeller selection alone will loose 5 MPH.

Victor, I quite agree with you and I think most people (including myself) do not experiment enough with different props. Yes, because it can be costly and also because when you think you've got it right, you leave it there. There are so many prop conficurations out there that I am sure if I played around a little more I could very well get just a little more efficiency that could perhaps sway me from considering a bigger motor for another year or two perhaps .

Victor, I have read in one of your posts that you firmly believe that the Mac boats need a 4-bladed prop. Can you perhaps elaborate a little more and explain why?

Octaman

[vkmaynard]

From the vast majority of prop tuners and install shops the word is "better hole shots, lower planning speeds, lost high-end mph" with a 4 blade prop. I saw this when we switched to a 4 blade on our Honda 50, except that the high end improved due to the Mac barge effect.

My degree was Aerospace Engineering so I'll tell you what I remember about propellers from a long, long time ago (sounds like bedtime story..yawn).

From a hydrodynamic stand point at high speeds, a 3 blade prop will interfere less with it's self due to cleaner flow between the blade thus better high end performance. This does not matter for a Mac. It is NOT a high speed boat. From a low speed stand point when there are more blades each one does less work which means that there is less pressure differential and better flow attachment (less cavitation also) which equals a more efficient machine, resluting in improved use of horsepower and better cursing gas mileage. The Mac lives in a low speed world. Put a 90Hp on a light weight 18' boat that run 50+ MPH then you will want a 3 blade prop.

When we bought our Suzuki 90 I had zero intention of using a 3 blade prop. The dealer saw our boat and immediately offered a 4 blade without asking. That is how they prop their non high speed boats. The prop tuner we used also recommended the same. How many other lightly loaded 26X (mast on and down, two batteries, 18 gal gas, two people @ 300lb, AC) will do better than 31 MPH with a 90Hp motor?

Victor

[Octaman]

Victor
Most enlightening point of view that I can readily understand having an engineering background myself; makes a lot of sense.
I think I may have to go back and try out a 4-blade prop on my existing Suzuki DF 70 (1.300cc) before I make the move to go up spending a few thousand Euros in the process. The 4-blade prop might just make the small difference I am looking for.

Victor, I have read all your postings on your new DF 90A and have to say I am impressed with this new motor and your resluts with the 4-blade prop.

Do you by any chance have/know of a chart that specifies the size of a 4-blade that corresponds to any given 3-blade. I would assume this exists somewhere.


Does anyone out there with an have any experience with switching from 3-blade to a 4-blade prop on their MacM?
I can't help asking (no offence to you Victor) as it has become clear over time that the behaviour of the is different to the (or vice versa if you like )

Any input will be greatly appreciated.
Octaman

[vkmaynard]

I can't help asking (no offence to you Victor) as it has become clear over time that the behaviour of the is different to the (or vice versa if you like )

I really could not comprehend the differnce until the day my wife shot this video http://www.youtube.com/watch?v=eovBozRo5gg

The M is definitely more of a displacement hull. You will notice how it plows thru the water vs. the X. One of our forum mates has a new DF90A on his M in Russia and is only seeing around 24 MPH with the same 4 blade prop. Don't know how much weight he has onboard. Not sure what the incremental improvement is between the 70, 90, 115, 140 on an M. The X shows a significant improvement with more power (90 is enough for us).

One thing I'll throw out for a 90+ Hp consideration; keep in mind high speed cruising (like our trips to Ocracoke and in the Chesapeake 45+mi). If you have a smaller motor it will operate at or near WOT (like the Honda 50) and eat a lot of gas and struggle to get you there. The newer Suzuki DF90A uses less gas in that case because it is not struggling (4200 RPM 18 MPH w/o ballast mast up boat loaded). If you get the X on a "real" plane (boat rides over the bow wave around 21+ MPH) then there is no challenge on fuel economy compared to a boat that is plowing thru the water. On a 45 mi trip (head wind, used motor) Billy (140Hp X) used about the same amount of gas at 24 MPH as we did at 13 MPH WOT on the Honda 50.

Victor

[Octaman]

Victor,
I read every word you write very carefully; your postings are most enjoyable. Thank you for being so precise and to the point.

The video I have seen many a time, over and over again and have made my obseravtions as well.
If I recall well enough the blue hull has a 2-stroke 90 E-Tec. The difference in hull behaviour is quite obvious. It is also very clear how you, on the filming boat, with the X can keep up with and overtake the M.

I am fully aware that my M will never become an X; I merely look for the motor that will fit best.

We don't have that many Macs in or around Athens, so I very rarely get to see what another Mac looks like powering. I cannot see myself (Ha, Ha) and I haven't had anyone shoot a video for me to make my own observations on myself.

However, it does seem that the blue M in the video is sitting a little low in the water, an indication that the boat is probably heavily loaded - that may need to be taken into consideration. Indeed I feel that I kick up less water with my smaller 70 hp engine; but I may be wrong. I can say that I have been very weight sensitive from day one being very careful of what I add on the boat (and what comes off). It does make a difference.

I tend to believe that the incremental results on an M should tend to improve drastically on the higher end of the hp scale. In other words, the satisfaction that you have experienced with the 90 on your X would require a little more hp for me to achieve on the M.
I have read Stefan's postings with his 90 hp M in Russia and have followed his accomplishments with great interest. The question is, can Stefan, like yourself, say '90 is enough' for him. Maybe it is too early in his Mac owning time. Would the 90 be enough for me? It seems like it could be the right compromise in every sense. I'm not sure.

Fuel efficiency is also very important and I would happily go a little higher if I were to save fuel.

And the quest goes on . . . .

Octaman