Engines

[Kim Forrester]

Anyone have an opinion on the use of the Tohatsu 70 hp TLDI on the M?[/b]

[DLT]

Yeah, you'll be dissappointed you didn't get the 90hp... Its the same weight. hull, its the same engine, just more HP... If you really don't ever want to use 90hp, you'll get 70hp out of the 90 at a lower and quieter RPM.

I put a 40hp etec on my boat. I'm kicking myself for not at least going with the 60hp, which is the same engine (much like the 70/90 tohatsu)...

[They Theirs]

I recall a post on the 70 vs. 90 hp differences. Though the 90 is rated some 20 hp greater, the power is all at the very top rpm, and not usable with installation on the Mac displacement. (More for a light plaining hull which could take advantage of power on the extreme end of the HP curve under some conditions.) The 70 that are a dealer install only according to BWY Todd for coverage above the 50 hp factory’s warranty limit.

[DLT]

the power is all at the very top rpm, and not usable with installation on the Mac displacement.

Huh? If you use the right prop, you should be able to get those RPMs...

[Kim Forrester]

I understand MacGregor doesn't provide a warranty on their boat for any engine over 50 hp. I assume that means anyone with more than 50 is on their own pursuant to warranty items on the hull etc ?

[ChrisNorton]

I'm convinced weight should be the determining factor on engines for the Mac as opposed to HP. I have a 1999 Merc 50HP Bigfoot. The thing weighs a ton and visiably sinks my back end low in the water. Two fully loaded 9 gallon tanks makes it worse. The thing is just too heavy and I think that causes more potential damage to both the boat and boat performance and Macgregor is just fine with it on the back end of their boats.

[RandyMoon]

Speaking as a guy with a 90 horse, it all depends how you are going to use the boat. If you are going to motor long distances, the extra horsepower is a big plus. If you are going to mainly sail, the extra weight is not worth it and I would go with a smaller/lighter motor.

My dealer installed the 90 and I have no worries about that size on my M. It is the same weight as smaller motors. One thing to consider though is that a M does not have a wide aft opening like the X does, so the more motor you hang on the back means less space to climb in and out of the boat if you go swimming. My 90 makes you squeeze in and out of the boat. A smaller motor would give more room.

[They Theirs]

[/b][/color]Posted: Fri Feb 24, 2006 10:54 pm Post subject: 90 HP outboard
Just thought I would answer a couple of your questions. First the reason that we are changing to the Suzuki 4 Stroke is in part that we are getting a little more speed, but mostly using significantly less fuel, and A LOT quieter than the TLDI or an etec. The Admiral (Cheryl) though that it was VERY important to be able to enjoy that 1200 Watt stereo system which we couldn't hear over the 2 stroke!.

As a point of note we even experimented with the TLDI 90 (we experimement with lots of things on The Pearl) as it was an easy thing to do, there is no difference between a TLDI 70 and a TLDI 90 except for the programing in the ECM and a throttle stop. Unfortunately we found that we gained nearly no speed configured as a 90 (though it did match the Suzuki 70) but it sure used fuel like a 90! The lack of performance increase is atributable to the fact that when configured as a 90, the TLDI motor produces the same torque as a 70, and torque moves these boats. We see about 22.5 mph fully loaded with the Suzuki, that's with bottom paint (coperpoxy) and the drag of the keel bulb. Our fully equipped but modestly loaded demo boat sees about 24-25.

Some of you have correctly figured out that the real issue is speed, not horsepower or weight. I have no concerns about the weight (other than the obvious, weight is never a GOOD thing, which is why we put the TLDI on The Pearl in the first place) of any of these 60 or 70 HP engines, the issue is flex in the hull bottom, not breaking the transom, and the potential for fatigue over time. We never put bigger than a 50 on an X as it's relatively flat bottom takes more of a beating as speed increases. The hull bottom on the M is a deeper V, reducing the loads on the hull structure, and it is also about 35% thicker than the X, making it a lot stronger.

The reason people have not had a lot of problems with overpowered X's is that they have obviously not been stupid. As a dealer or manufacturer, we cannot put an engine on a boat that gives someone the power to beat the boat to death if they don't back off when they should.

Also, with all things set up right, the performance of a Suzuki 50 and either the old Nissan / Tohasu 50D or the TLDI 50 is identical (within .5 mph), if people are finding more difference than that, it's either setup, load, or bottom condition.

Hope this answers some questions

[Bobby T.-26X #4767]

Anyone have an opinion on the use of the Tohatsu 70 hp TLDI on the M?[/b]

i noticed that you live in Colorado (a mile high).
that being the case, if i wuz u, i'd go with the Evinrude Etec product. it really performs alot better than the Tohatsu product at altitude.
the 75 & the 90 Etec have the same powerhead and same weight (abt 315#).
therefore, i suggest that u go with the 90.

BTW...i have a hard time agreeing with the quote above from BWY Todd. I've seen that qoute before on this site and I just do not buy it. The Suzuki 70 is very quiet around the harbor, it is indeed. Like the Suzuki 50 around the harbor. But so is a Honda 4 stroke 250. yes, i said 250. all the 4 strokes purr at idle speed. where as the 2 strokes are a slight bit less smooth.
yet at WOT, the Suzuki 50 or 70 is every bit as louad as a Tohatsu 70/90 or Etec 75/90.
the Suzi 70 (if you've ever seen it) is HUGE (both size and weight).
it will not push a mac at the same speed as a Tohatsu 90...never!

Bob T.
"DaBob"
'02X w/ '04 90-TLDI & '06 2.5-Suzuki

[Dimitri-2000X-Tampa]

and it is also about 35% thicker than the X

Wouldn't this add a lot more weight to the M boat? If I recall the literature correctly, there is only an extra 300 lbs over the X boat which is due to heavy fiberglassing around the base of the dagger board trunk (also acting as permanent ballast).

[They Theirs]

One of the Benefits of Technology….
The structural strength has been applied by space age computer software…. Applied to benefit the new design.
"M" Model


"X" Model

[DLT]

We've seen that quote from Todd and BWY before. However, there was never any determination as to whether they used a different prop with the 90, as opposed to the 70. Their results are exactly what I'd expect if they used the same prop... Since the 90 was just a temporary trial, to say nothing of their motivation for conducting the "test", I'd bet they didn't get a different prop...

By the way, the 90 weighs exactly what the 70 weighs (tohatsu, that is...)

Bottom line, as you asked for opinions, there is no way I'd make the same mistake again. If I were considering the tohatsu 70, as you seem to be, I'd go with the tohatsu 90, as there is no weight penalty. It will cost more, but it would be worth it for me. At the very least, even if you never use all 90 horses, you'll be able to get 70hp at a lower RPM and noise level...

From what I here, from tohatsu 90 owners, its great motor and they all seem VERY happy with it. Its also gonna be significantly cheaper than the 90 ETEC.

[They Theirs]

I suppose there could be substance in that you’ve questioned BWYTodd report for the error in his propeller selection. Knowing he has the skill and ability to test first hand on the stock boats and the experimental craft, and provide his finding at no financial gain, (Surely your words, the larger cost more) providing what I suspected in computer controlled injection systems. The larger engine uses more fuel because it needs a longer injector dwell and fully opened throttle to produce more top end revolutions, (Remember Engines are Compressors) in claiming a whopping 22% power increase for an engine of the same weight and internal volume. Surely there could be error in results from first hand testing, and this fact cannot be overlooked, but coming from what has been a reliable source leaves little doubt in his candor.

Information we have "On Going Bigger!"

We have verified results it uses significantly more fuel than a 4 stroke.

We know the extra Power, but same torque, will provide little increase in speed.

We know the TLDI is much louder than the 4 strokes

We know there is little boat speed gained by upgrading from 70 to 90.

We know the 90 cost significantly more than the 70

We have Todd & Randy Moon providing advice: "Sails better with smaller engine"

We know the larger engines are significantly larger in size, filling the motor well.

We know the Factory Warranty is only good for 50 hp.

We don’t know if a different prop will produce an incremental gain

[Bobby T.-26X #4767]

Information we have "On Going Bigger!"

We have verified results it uses significantly more fuel than a 4 stroke.

We know the extra Power, but same torque, will provide little increase in speed.

We know the TLDI is much louder than the 4 strokes

We know there is little boat speed gained by upgrading from 70 to 90.

We know the 90 cost significantly more than the 70

We have Todd & Randy Moon providing advice: "Sails better with smaller engine"

We know the larger engines are significantly larger in size, filling the motor well.

We know the Factory Warranty is only good for 50 hp.

We don’t know if a different prop will produce an incremental gain

Good thread and good discussion...

the word "significantly" is used extensively in the above quote.
my comment is as follows:

- regarding fuel use: my 90 TLDI at 20mph and 3/4 throttle goes 20 miles on 6 gallons versus my previous Suzi 50 at 15mph and WOT going 25 miles on 6 gallons. Is that significant? not for me...

- regarding noise: around the harbor at 1000 RPM or less, the 4 stroke is king! that is very smooth and quiet. as previously stated, even a Yamaha 250 4 stroke is smoother that my TLDI. However, at WOT or 3/4 throttle, the new tech 2-strokes are no different in noise. they are not "much" louder. at least in my experience.

- regarding 70 vs 90 boat speed: put me side to side with a 4 stroke Suzi 70. no comparison...

- regarding cost when upgrading to a 70 vs 90: the tohatsu/nissan web site lists actual suggeated retail pricing. it's $1000 more. you will probably pay $5-600 more on a $8000 purchase. what is that...7%? where i come from 7% is not significant...

- regarding sailing speed: i would suspect that everything else being equal...a 9.9 horse would sail the fastest. but then why own a mac if you're not taking advantage of it's motoring features?

- regarding engine size: my Tohatsu tldi 90 is 60# heavier, a little bit higher and slightly wider than a Suzi 50. i would not say that it is significantly larger.
the Suzi 70, however, is very heavy and very large. the Suzi 70 does fill the motor well. the Suzi 70 is significantly larger than the 50 (nearly 100# and twice the size).

- regarding factory warranty: only original purchasers for a period of two years are eligible. i purchased my X used so i was never eligible for a warranty.
there has been some talk on this site about certain dealers being allowed to install 70hp motors and still offering the standard warranty (even though the motor is more than the recommended 50hp). although nothing in writing in any of the manuals or contracts has ever been produced and shown on this web site, it's just been discussed.
Mike Inmon ( a premier SoCal dealer) has tested several large motors on the back of M's including an Etec 90. but i have not heard about him ever promoting/endorsing (probably a liability issue) anything larger than a 50.

- finally, regarding props: my experience has been that whether you have a 50, a 70, or a 90...you should incorporate a prop with large surface area (a pontoon style prop) so that you can push this "monster" within the engine manufacturer's recommended RPM range and without cavitation.
some use a higher pitch (13) to get better speed while "lugging" the engine. i recommend a 11 pitch for a 70-90 hp (sometimes 10 or 9 work on 50's) to get max speed and rpm's.
in my opinion and experience, a different prop can realize incremental gains.

Bob T.
"DaBob"
'02X w/ '04 90-TLDI & '06 2.5-Suzuki

[Frank C]

We've seen that quote from Todd and BWY before. However, there was never any determination as to whether they used a different prop with the 90, as opposed to the 70. Their results are exactly what I'd expect if they used the same prop...

DLT, there are 2 reasons it seems unlikely they used the same prop:

1. Most new motors include a new prop, so no reason to use the same prop;
2. Tohatsu and Suzuki use a different hub (at least, per Pirahna's webpage).



As for the Suzi-70 vs T-90 debate, IIRC the BWY Admiral found little need for all-out speed, but wanted a quieter motor. Mid-range cruising IS less noisy with a 4-stroke. I'd guess that most large motor owners don't run at nine-tenths. Fact is, the hope of avoiding max operation was a major bullet point for my choice of the S-60 ... reasonable cruising speed (15 mph @ 3800 rpms) means I very rarely use WOT. I sensed similar decision factors in Todd's post. Finally, I finally had chance to ride in an eTEC 50 this season, pushing a 26M. It's a great motor for a great boat, and it's not extra noise that would deter me ... but I feel one can definitely smell the 2-stroke exhaust. That's definitively a non-issue with the EFI 4-stroke.

Pros & Cons: noise / weight / bulk / economy / speed / aroma ... mix yer own poison!