What are your top speed & cruise #'s

[Gazmn]

This is a somewhat belated followup regarding my 90 E-tec.

I had my boat shop hook up the motor and check everything. On computer it's running fine. All pistons firing. I have 7 hrs on the motor. I'm still in its unofficial breakin period. While I can run it WOT there's still a 20 hr break in for getting your set #'s.

Boating improved greatly with a 14 x 11 prop. I just ordered the Evinrude pontoon prop in a 14 x 11. But it'll have to wait for next season

My installer says there's no way you're getting a 4000 lb boat @ 26ft up in the high 20 - 30 mph [25 knot] range. And I have to agree with him. I don''t know what our hull speed is; I forgot the formula -- Anyone?

I'm very thankfull for the new motor. I have a heavy bote. I think it's time to just not believe the hype that this thing will fly with a 90.

I cruise comfortably @ 14 kts. That's nothing to sneeze at. You still tend to keep it <10kts - unless you like getting wet.

I'm hoping my next two Big mods will be Tony Houks Smartrail. With rails at the waterline to bring the boat up off the water & drier and the Keel guard.

- Not so much for beaching, as I'm not up to that, yet. But because my 10 Y/0 Mistress is getting ugly from banging up the trailer

In short for those looking for 90 Hp upgrades. Yes, it's fast-er, But it doesn't have wings; So Buyer Beware [ I can't spell in French.]

I'm just happy to be here - With a new "Wurkin" E-tec


Cheers

[delevi]

Gazmn,

I still think something is very wrong. I have an Etec 50 which came with a 14x13 prop. I downsized to 13.5x13 due to my heavy keel. I easily get 16 mph (14 knts) in big current and frequently hit 18-19 mph (about 16 knts) In smooth water, I can get 20+ hitting 22 mph on one occasion. All figures are without ballst. With ballast, I get 3-4 mph less. You should be able to hit 30 mph with that 90. Perhpas you should be looking at a much larger prop. More like a 17x13. Currently, you're using less than what I have on my 50. Just one thought.

One Edit:
Your RPMs may be topping out due to the limits governed the engine's computer. You can probably spin a much larger prop with those same RPMs, therefore getting much more speed.

On Further Edt:
Don't buy the dealer's BS about breakin. Evinrude advetises that there is no breakin period on these engines. They're ready to go WOT right out of the box and zero maintenance for 3 years. Check out their web site. Again, I think you need the big prop. If that isn't the answer, there is something seriously wrong with the engine.

Aya,

Thanks for the flushing tip. My dealer was quite atimate about how cool this engine is since you really have no need to flush it. I noticed, however, that other boats owners in my marina with Etec engines flush theirs. I haven't considered the marine growth. Perhpas I'll flush. OK, no toilet jokes

Leon

[Robert]

Gazman, I suggest that you prop your 90hp so that the motor reaches the top of its wide open throttle RPM range with the ballast full in smooth water conditions. This will provide the most Hp because Hp is proportional to RPM.
..
http://www.brp.com/en-US/Products/Evinr ... tID=ETEC90
..
The lower pitch larger blade prop will not limit your top speed on a Mac26. The Mac26 is not a 45mph power boat, it is more like a slow pontoon house boat. The Mac26 does not have a power boat planing hull. The logic of less prop drag to let you go faster does not apply, big blades and low pitch for less prop slip and more RPM=more Hp is the way to go.
..
The power required to go fast on the water is not linearily proportional to speed, more like as the square of speed, so to go twice as fast you would need at around four times the power. My Suzuki 50hp on smooth water could go 16.5mph with ballast full, so to go 32mph with ballast full I would need 200hp.

[Gazmn]

Thanks Delevi & Robert,

I don't think anything is wrong with the engine. I think I was expecting too much.

I would like a 14 x 10 for 5500 RPMs & full ballast. [ ala Robert] My last run was on a bad day:18kts @ 5300 RPMS, unballasted. in moderate chop & windage.

I now think 18kts is pretty good. I thought [similar to Delevi] that a 90 would blow the doors of a 50 or a 60 E-tec.

But now I think it's as robert said:

The power required to go fast on the water is not linearily proportional to speed, more like as the square of speed, so to go twice as fast you would need at around four times the power. My Suzuki 50hp on smooth water could go 16.5mph with ballast full, so to go 32mph with ballast full I would need 200hp.

So you go faster, but not by all that much with a 90 vs a 60. Plus I run with three Batteries, 10 gal of water and bunch of stuff I need to pull from the boat - & I'm 210 lbs - As are my supersized friends

So it seems a 90 will get you to about the advertised 20kts loaded. But you Still are not a PowerBoat.

[Catigale]

Gazm - your hull speed is

4/3 * SQRT( Length at waterline) or about 7mph for a Mac, but this only applies in displacement mode. With the speeds you are discussing, the hull lifts out of the water and the formula no longer applies.

A bit of a warning flag......

An installer who doesnt know the difference between displacement and planing modes probably hasnt been around boats much...

[TonyG]

2005 Mac, 2006 ETEC 75, 14x11 prop.lightly loaded.
25 mph@ 5000 rpm. With GPS , two way average.
Wouldn't want more power. The best outboard yet.

[delevi]

I still think you should get significantly better performance from your 90 than what you're getting. Your expectations were not unrealistic. See above post on the 75 Etec, much better than what you're getting on the 90. I tried a 14x11 prop and got terrible performance, RPM over 6000 and top speed around 17.5. Compared to 13.5x11 giving me 20 mph lightly loaded at 5600 rpm. These Etecs can push a big prop. Try it. I don't think you'll be disappointed.

You may also consider this adjustable pitch prop: http://www.propulse.se/

Leon

[trumpetguy]

I have a new Suzi 70 with a 13.5X13. WOT is 5200 RPM. With a moderate load and no ballast I can get 20MPH on the GPS. I will probably pitch down to 11 and achieve higher RPM.

[Frank C]

As I posted elsewhere, 14x11 seems to be the Mac-magic prop. Even 75 and 90 horse motors are achieving recommended max rpms with that size prop. However, it's also important to recognize that a 14x11 prop does NOT always equal another 14x11 prop. Further, prop diameter and pitch doesn't necessarily describe the beast.

I recently ordered Piranha's new 11-inch blades and my Suzuki 60 just ventilates it like crazy after 4000 rpms ... too little pitch for the blade size! As others have posted above, the "pontoon props" are frequently available in 14x11, with those big, dog-ears. THAT seems to be the secret sauce for these Waterbagos ... semi-displacement hulls with lots of weight, and lots of wetted surface.

Why can Leon get such great speeds from just an ETEC 50? Not sure, but the next question is, "How is speed measured?" Many other factors also bear on that performance - loaded weight, placement of load ... maybe the motor mounting details. His dealer, Arena Yachts, was the first Mac dealer to ever mount a Bigfoot and they had lots of prior outboard experience before becoming a Mac dealer. Who knows ... maybe a pontoon prop on Leon's boat might give even better performance than that current 13-pitch.

[Bobby T.-26X #4767]

Waterbagos ...

LOL
excellent description!

[danboltonnewby]

Just before the end of the season I did a little experimenting with props for the Etec 50 and my Mac 26M.

I took out all the gear and ensured the ballast was completely empty with only me onboard and hardly any fuel (just enough to be experimenting).

After trying a few the best results seem to be with the 3 blade, big dog ears, 13.75 diameter x 13 pitch. This pushed me at 20.5 mph with my rpm's at 5400.

The only other prop that came close was a 3x14x13 and slight cup?!. The blades were not the oversized big dog ears though and the prop shop had given it a slight cup because his thinking was that my rpm would drop as I go up in diameter, (even 1/4 inch) so said if slightly cupped it would keep the rpm up?! Still not sure about that...

This prop gave the same speed, but only 5200 rpm, so seemed to may the engine struggle more to get the same job done.

I thought about when I put all the gear back in the boat and have passengers the rpm would drop anyway as the engine struggles to push the extra weight.

The dealer mentioned that the engine is only giving me 50 horses at the engines max rpm, if running at a lower rpm that max, you're not getting all the 50 hp of power.

The only thing I can think about that I have not yet tried, would be to use a 3 blade x 13.75 diameter x 12 pitch, and to make sure the blades are the big dog ear type.

Dealer mentioned that you gain 500 rpm for every inch of pitch your drop. This would give me 5900 rpm (in theory), and maybe a couple of hundred less when the boat gets all the gear (and passengers) back in it.

Does this sound about right? Make sense??

Oh and the other thing I found during the experimenting was that when my friend was onboard too, the speed went down by 1mph.

So I am starting to think that one you find the ultimate prop for your situation the next thing that relates to keeping the speed up is keeping the weight down.

If you loose 1mph with a 180 lb guy added, you'll probably loose more with a loaded boat and a few people, especially if you have arranged to be at the max rpm with the boat empty. As mentioned before about not getting your full team of horses to play until the rpm stays up there

[Terry]

Dealer mentioned that you gain 500 rpm for every inch of pitch your drop. This would give me 5900 rpm (in theory), and maybe a couple of hundred less when the boat gets all the gear (and passengers) back in it.

Does this sound about right? Make sense??

I read that 2 inches of pitch gives you 300-400 rpm +/- but discovered it is not linear in my own experience. There are many variables that affect a propellers performance, read this site:
http://powerboat.about.com/od/propeller ... ellers.htm
One thing that appears to be a common denominator for everyone is the blade surface area, as in pontoon props, dog eared, or 4 blades, the more surface area seems to equal better efficiency. I also found that with the Honda 50 that a slightly smaller than 12" diameter (11.4") reduces chances of ventilation. I noticed at top speeds that the anti-cavitation plate skims/planes the water surface so it may be wise to have some clearance between the prop & plate.

[Bobby T.-26X #4767]

I noticed at top speeds that the anti-cavitation plate skims/planes the water surface so it may be wise to have some clearance between the prop & plate.

i cannot comment on that.

but what i do know is that even a 90hp is not enough to power a boat the size and weight of a Mac at the level that most on this board desire.

to get the best results with anything 90hp or below...go with a pontoon style, big dog ear prop. get the largest diameter possible and the largest blades available.
for most applications...a 12 is the maximum pitch.

[Terry]

Bobby T.
I have to agree with you on the largest diameter, dog eared, pontoon style prop. My comment on clearance for the anti-cavitation plate stems from the ventilation problems some folks have had with the Honda 50. There is only 6.25" radius to the plate on a Honda which restricts diameter to a 12" max diameter leaving only .25" of clearance to the plate. The Honda plate extends barely an inch below the bottom hull center at the transom, and this contributes to ventilation at higher speeds especially while cornering since the plate does skim the water surface at higher speeds. If the skeg was a bit deeper say 2" it would not be such an issue, but with the current set-up I have found that decreasing the diameter to 11.5" has helped reduce the ventilation problems. To compensate for the reduced diameter I went for a large eared 4 blade medium cupped propeller.
When the day comes to replace my Honda you can be sure my engine selection will swing a 14" propeller. Perhaps by then a 90 hp will come in at less than 300#, I like the extra HP but not the extra weight so much.

[Frank C]

Terry,

Maybe your motor mount needs to drop by one more bolt-hole,
thereby submerging the anti-cavitation plate by another inch, or so?