MacGregorSailors.com

JMHO, from my personal experience.

When I bought my Merc 75, I would have preferred to have found a good deal on a 90. Same weight, 15 more hp, why not? Many here have 90hp OB’s with much success. I am now thinking, based on my experience, that I am very glad I ended up with the 75 instead. Here’s why..

- it would seem the Mac is a heavy boat for any hp OB and needs a good push to get her going, I conclude the more cc’s the better, ie as much torque as possible.
- My Merc 75 has exactly the same spec as the same year 90 model, except max rpm spec being 4500-5500 on the 75 and 5500 to 6500 on the 90
- To get 90hp out of the 90 you need to get to that higher rpm, ie you are not getting 90hp at 4000rpm
- When I played with the pitch of my prop from 13 to 11, I found slower speeds across the board form the 11 than the 13 at any given rpm
- My 75 just gets to 4500 fully loaded with a 14x13
- If I had the 90, I could not get beyond 4500 rpm, outside of spec, so I would have to use the 14x11
- Having the 90 would result in a higher top speed no doubt, but then I would loose the advantage 75 14x13 of going faster with less noise, rpm, fuel econ, wear and tare, all important things to me.
- My 75 already takes the Mac above its suggested top speed, ie how fast is too fast?

I just thought I would post my findings so anyone buying a new Mac or re-powering would have some food for thought. The new Honda 75/90 is not in the same boat, so to speak, as they have no difference in the spec’s other than magically getting 15 more ponies from the same motor.

Cheers

G

With my 90 hp tldi tohatsu, I averaged 18.5 KNOTs (over 20 mph) to and from Catalina (21 miles each way, perfect conditions) last weekend. Burned 7gallons of gas each way at 4000 rpms.

Mast up, 80 pound inflated dinghy on bow, bout 600 pounds of people and stuff(including me) on board.

I have video of my mac keeping up with the Catalina express, which goes same speed. WOT I did 21 knots (24 mph). The 90 transforms the macx into a true powerboat with great sailing capabilities, just like the old brochure claimed.

Rolf

BTW, Cabrillo launch is now computer controlled parking, $15 a night.

Rolf;

WOW on the Cabrillo parking

WOW on your gas mileage also

Rick

beene wrote: The new Honda 75/90 is not in the same boat, so to speak, as they have no difference in the spec’s other than magically getting 15 more ponies from the same motor.

there's no magic about the differences here. the 90 is inspired by VTEC technology, the 75 is not...

Boats.com on the 90 vs 75 wrote: This engine has all the techno bells and whistles Honda has installed on its more-recent outboard designs, including electronic fuel injection, VTEC variable intake valve timing, and a lean-burn system that improves fuel economy. It also features a patented ignition timing system called BLAST (Boosted Low Speed Torque) that is supposed to improve initial acceleration.
VTEC gives this motor two intake cam profiles, short duration for smoother operation at lower speeds, and long-duration for more power, engaged by the computer at engine speeds above 5300 rpm. A Honda insider tells me VTEC is worth 12 to 15 additional horsepower at wide-open throttle — this "90-hp" model actually makes 97 hp at 6000 rpm, seven more horsepower than the old BF90.

if i was in the market today, the Honda 90 VTEC would be my choice.

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

beene wrote:- My 75 just gets to 4500 fully loaded with a 14x13
- If I had the 90, I could not get beyond 4500 rpm, outside of spec, so I would have to use the 14x11

IMHO you are a bit confused...

1) a 75hp outboard is not made to push a 3500# boat for extended periods at the low end of it's RPM curve. most technicians will insist that for your particular application (pushing a "waterbago" with an undersized motor) and to prolong engine life, you should utilize a prop that will get you to the highest end of the RPM range under loaded conditions. it has been suggested to me by my outboard motor manufacturer that i choose a prop (a pontoon/work prop) as if i was pushing a houseboat.
based on your RPM info above (4500 RPM's at WOT), i believe that you are shortening engine life.

2) a 75 is a "de-tuned" 90 (or a 90 is an "up-tuned" 75). although prop choice has a role in overall performance, your statement above indicates your belief that in a test:
- same Mac
- same prop
- one with 75 vs one with 90
- equals same RPM and speed at WOT
i believe that the results will be different as the 75 and the 90 have a different CPU.

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

beene wrote:- My Merc 75 has exactly the same spec as the same year 90 model, except max rpm spec being 4500-5500 on the 75 and 5500 to 6500 on the 90

Incorrect. The minimum max rpm range of the 90HP Mercaha was only 500 rpm higher, 5,000 to 6,000 rpm.

beene wrote:- If I had the 90, I could not get beyond 4500 rpm, outside of spec, so I would have to use the 14x11

Also incorrect. The reason the 75 peaks at the horsepower it does in the range it does is because the torque curve is falling as fast or faster than rpm is rising. The 90 has higher torque above that rpm range, so it delivers more horsepower and would continue to increase the rpm and hence boat speed with the same 13" prop.

beene wrote:- Having the 90 would result in a higher top speed no doubt, but then I would loose the advantage 75 14x13 of going faster with less noise, rpm, fuel econ, wear and tare, all important things to me.

No, you wouldn't have lost these. No disrespect intended, but this line of thought may make you feel better about having the smaller HP, but it simply isn't the case. It's sort of like using your level waterline (compared to other 26Ms) when the cockpit's unoccupied to rationalize the grossly overweight outboard. If I HAD to put 90HP on a Mac, it would be the much lighter E-TEC. That said, if you're happy with it, fine.

Bobby T.-26X #4767 wrote:...most technicians will insist that for your particular application (pushing a "waterbago" with an undersized motor) and to prolong engine life, you should utilize a prop that will get you to the highest end of the RPM range under loaded conditions.

In the case of most Macs, where most of the operation is under heavy load forever climbing the bow wave with full down trim, I agree with that and prop accordingly. With pure powerboats, where most operation is up on plane with the outboard trimmed up and more lightly loaded, propping for the bottom of the max rpm range is okay... if you aren't pulling tubes or skiers.

... the grossly overweight outboard. If I HAD to put 90HP on a Mac, it would be the much lighter E-TEC. That said, if you're happy with it, fine.

Have to disagree a little here, when other power boats in the size of the Mac (26 feet) are running 1900+ lbs of outboards (triple verados in the 300hp range) the Mac is far from grossly over weight from the outboard that weighs in at 315 lbs. Macgregor only states that a 50hp weight wise is preferred as its easy to take off the boat and service. Nothing stated about saving weight because the boat cant handle the extra 100 + lbs. with a 90. Also moving weight forward will offset the extra 100lbs of outboard. so instead of putting your dinghy below in the back bunk put it on the bow. Besides the M is bow heavy in the first place so the extra weight of the 90 or 75 will help balance it out some.

The Mac will plane very well with a 75 or 90 and the waterbago turns into a respectable cabin cruiser with these lesser hp engines, pushing the Mac to a very nice cruising speed of 20+mph in open ocean.

If I had to I would opt for a 90 or 75 (anything over a 50) in any make. because the mac wakes up (pun intended) with these feather weights, at least in the overall outboard categories.

also the mac is planing at 17mph shes right up there and you can feel it. she steers better holds course better and the bow comes down. But because of the hump therory that has been displayed on these boards we tend to think shes not planing, but seat of the pants will tell you it is. so the pretty graphics displayed here about planing are really just that, pretty. When the steering is easier and the boat feels lighter and tracks better shes on plane. A 50 will get her there but wont hold it like a 60-75-90. Thats a proven fact.

as far as triple 300hp verados, well we are still a sail boat.

Planing: There is a big difference between a performance power boat (bass boat) and a large boat like a Mac. A performance boat has a pad at the back of the boat built in that when on plane will ride just on that pad. the bass boat will not float on the pad. It needs to climb up on it.

The pad is at the very back of the boat and is about 1/4 of the length of the boat or less. On larger boats like the Mac or just about any cabin cruiser there is no pad almost the whole bottom of the boat is designed to ride up on top of the water when planing. So the hole theory only works when you have a pad. Because the performance boat cannot ride on that pad unless theres enough power to get it up on it the boat digs a hole it has to climb out of. Not the case for a hull that floats on all of its planing surface in the first place. The mac or any other larger planing boat will dig a small hole but not anything like a performance boat does. so the Mac does not have to "climb out". You can feel this when you guys with the extra power get on plane you can actually back off on the throttle a little and still maintain the plane, unlike us little hp guys who just hit the mark. But you cant back off like you had a pad or you will slow down alot.

When you think about it the mac with the very small hp actually does a great job. Compared to larger power boats. even a 90 on a similar size power boat wouldnt even start to get them on plane. And we have masts and other things that hinder performance. Thats because the hull shape and weight of the boats but I would say the design has a lot to do with it. not an easy thing to make happen.

Hi Bobby

there's no magic about the differences here. the 90 is inspired by VTEC technology, the 75 is not...

Thanks for that clarification. I went to the Honda site and opened a page on the 75 and another on the 90. Both on the spec's pages. Flipped back and forth, looking for a difference, kind of like my 75/90 Merc manual, I did not see any diff, line for line, so I was baffled as to how they got the extra 15 ponies. Did not notice that one was a Vtec and one was not. Leave it to Honda to sweeten the pot making you pony up for the EXTRA!!

if i was in the market today, the Honda 90 VTEC would be my choice.

So, even though you have a TLDI 90, you would recommend the Honda over yours? Could I ask why? Sorry if you already explained somewhere else.

based on your RPM info above (4500 RPM's at WOT), i believe that you are shortening engine life.

I only open her up to WOT once in a while to keep her clean. When I do, it's just for a minute or two. I, like every powerboat owner I have ever had the pleasure of talking to, cruise at less than WOT. I spend all my time at 3700 or less. I agree it is harmful to the engine to not be able to reach the rpm spec range at WOT, that is why I am happy that I can, even if only the bottom end of the range, I only need to hit it for just a minute.

So in aswer to your statement ..

a 75hp outboard is not made to push a 3500# boat for extended periods at the low end of it's RPM curve.

.... I don't. I spend hours at 3700rpm, and when I use a 14x11, I get 2.5 mph less speed at that rpm.

a 75 is a "de-tuned" 90 (or a 90 is an "up-tuned" 75)

My manual, contrary to others information, shows that the only difference between the 75 and the 90 of my model is max rpm 4500-5500 and 5500-6500. I spoke with 3 different mech's at three different shops. Guess what, I got 3 different statements as to what the difference was between the 2 motors. The 3 seemed to agree that the 75 has a rev limiter that stops her at 5500rpm. So I asked if that could be removed, all said no way Jose, with a smile.

- equals same RPM and speed at WOT
i believe that the results will be different as the 75 and the 90 have a different CPU

I have stated that the 90 would have a higher top speed, no doubt, but I think it needs the 14x11 to get it there nicely. If it is anything like a motorcycle engine, ie max hp at higher rpm, it won't get there with the 14x13.

BTW
I think you have a great motor, good choice on ya mate.
You have posted many threads on how happy you are, I am happy for you. I am sad for those that have less and can't enjoy what the Mac can really do. I feel their pain. I would be pi$$ed if I was in their boat, so to speak.

G

Moe wrote:

beene wrote:- My Merc 75 has exactly the same spec as the same year 90 model, except max rpm spec being 4500-5500 on the 75 and 5500 to 6500 on the 90

Incorrect. The minimum max rpm range of the 90HP Mercaha was only 500 rpm higher, 5,000 to 6,000 rpm.

Moe
Why do you post in this manner If you have access to better information than the manual that came with my motor, great! I am very happy for you. When I posted that information, I did not make it up, I got it from my manual.

Moe wrote:Also incorrect. The reason the 75 peaks at the horsepower it does in the range it does is because the torque curve is falling as fast or faster than rpm is rising. The 90 has higher torque above that rpm range, so it delivers more horsepower and would continue to increase the rpm and hence boat speed with the same 13" prop.

Ok, I based my statement on the facts in my manual. I concluded after speaking with 3 mech's that since the only obvious difference was another 1000 rpm, and that torque is more a function of CC's not hp, of which I have the very same, the 90 would not reach rpm spec without going to the 14x11 under the same conditions.

Moe wrote:

beene wrote: - Having the 90 would result in a higher top speed no doubt, but then I would loose the advantage 75 14x13 of going faster with less noise, rpm, fuel econ, wear and tare, all important things to me.

No, you wouldn't have lost these. No disrespect intended, but this line of thought may make you feel better about having the smaller HP, but it simply isn't the case.

So you are saying with the Merc 90 of my model year I could get to 5500 rpm with the same prop I am using under the same loaded conditions? I do not see that as being possible, no way, no how.

Moe wrote: It's sort of like using your level waterline (compared to other 26Ms) when the cockpit's unoccupied to rationalize the grossly overweight outboard. If I HAD to put 90HP on a Mac, it would be the much lighter E-TEC. That said, if you're happy with it, fine.

I simply noticed that the waterline on the Mac M seemed bow down in most pics I had seen, compared to and X for example, and mine went from bow down to level with the heavier motor, sorry if that upset or offended you in some way. As far as "Grossly Overweight OB", it is not that much heavier than the Suzi 70 that BWY mounts and I take their experience with the Mac M over anyone else's.

G

Hi Rolf

With my 90 hp tldi tohatsu, I averaged 18.5 KNOTs (over 20 mph) to and from Catalina (21 miles each way, perfect conditions) last weekend. Burned 7gallons of gas each way at 4000 rpms.

Those are FANTASTIC numbers.

I spend all my motor cruising at 3700, 19.5-20mph, heavily loaded, and get about 5 mpg, so about 35 miles on 7 gal, give or take.

Cheers

G

Hi Mike, nice to hear from you again.

The Mac will plane very well with a 75 or 90 and the waterbago turns into a respectable cabin cruiser with these lesser hp engines. pushing the Mac to a very nice cruising speed of 20+mph in open ocean.

Too right mate.

However, she is very sensitive to weight placement in the cabin. I find that location for the cooler, you know, the cushion cut out in the aft berth, not good. I notice a BIG difference between putting a heavy cooler there and moving it more fwd on the floor of the cabin for example.

G

beene wrote:So, even though you have a TLDI 90, you would recommend the Honda over yours? Could I ask why?
G

my ideal mac motor would be a 75-90hp 4-stroke that weighs under 300#.
such an animal was not available when i repowered in '04, so I went with the next best thing at the time, the 2-stroke Tohatsu 90-TLDI.
since then, the 2-stroke 90 ETEC has come into play.
and now it's the 359# Honda 90 4-stroke. so for the time being, that's my top choice.

i'm guessing that somebody will very soon get under 300# with a 4-stroke 75/90hp. if i'm still in the mac game, i'll repower with that one.

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

Thanks Bob

Just seems like you have such a great combo already.

For me, I will re-power when HFO or my motor blows up, which ever comes first.

G