etec pontoon series

[csm]

Hello all,
after months of exploring options, I decided to pull the trigger on a 90 etec, only to be faced with a dilema; the PS. An additional $235, buys "softer" engine mounts to reduce vibes, "optimized" gear ratio to allow a wider prop selection, and "special software mapping". The price increase isn't a huge issue, and reduced vibration has the be a plus, but the dilema is the pros or cons of the reduced gear ratio. I have an extra 13 x 15 three blade stainless prop, I was planning to useon the standard 90etec, but that probably isn't optimal with the PS reduced ratio. I can juztify an additional $235 + $400 for another prop if it will buy increased performance/economy. I'l be pulling wake boarders/ tubers occasionaly, but low speed handling (especially at the dock) and economy take presedence. Real life experience greatly appreciated, but wild speculation is also way cool

[Tomfoolery]

Since the pontoon series has a higher gear ratio than the standard version, it will swing a larger, high-thrust type prop at lower speed, which should be what you want for towing skiers and tubes. I would think it would be just the thing for the Mac power sailers, including for docking. Like the Big Foot outboards.

[mastreb]

I wouldn't do it. Basically the motor is optimizing for more torque, and frankly the ETEC family already has a lower gear ratio than any of the 4-strokes out there (2.6:1 vs. 2:1). The performance of the ETEC-90 on a Mac is pretty damned close to ideal in terms of fuel usage for speed, which is what you're real measurement is on a boat.

I'd stick to the known working. Pontoon boats have a whole lot more drag than a MacGregor hull, which is why they've optimized the engine for them. You can prop it differently to compensate but you can't change the "special engine mapping" whatever that is. I can imagine that that's only for increasing torque.

The engine mounts sound pretty cool though

[vkmaynard]

I wouldn't do it. Basically the motor is optimizing for more torque, and frankly the ETEC family already has a lower gear ratio than any of the 4-strokes out there (2.6:1 vs. 2:1).

Actually the Suzuki DF90 has a 2.59:1 final gear ratio. http://www.suzukimarine.com/Product%20L ... DF90A.aspx

The Mac M is more like a pontoon boat with its' displacemet hull. Our dealer gave us a 4 blade pontoon prop before I asked. Runs great. I doubt you could get any more out of this engine on our boats. http://m.youtube.com/watch?v=HqKgqweVZVQ

The pontoon series sounds like a good possibility. Only one way to find out.

Victor

[csm]

I neglected to mention that I'll also be trolling at speeds of 1.5 to 3 mph. Think I'll see if someone in the BRP engineering dept will talk to me. If I can get through, I'll post their recommendation.
Thanks all

[Seapup]

Since the pontoon series has a higher gear ratio than the standard version, it will swing a larger, high-thrust type prop at lower speed, which should be what you want for towing skiers and tubes. I would think it would be just the thing for the Mac power sailers, including for docking. Like the Big Foot outboards.

I am of the same school of thought, the mac is a sailboat and a barge. I would think it would actually have much more drag than a pontoon until or if you can get enough of the hull out of the water and on plane. The larger the diameter prop you can turn with less slip the better. More control docking and better efficiency cruising.

the dilema is the pros or cons of the reduced gear ratio.

The pontoon series has 2.36 vs 2.01 gearing. Since the lower gearing only lets you turn a larger pitch but not a larger diameter the results may not be much. I don’t know if the 13x15 prop you have is a good pick unless it’s a 13.75” diameter. Prop design varies, but a big advantage of the larger motors is the torque to swing a 14” prop. I know Gazmn with an etec 90 on his boat suggests the 13.75x13. (same prop as the 60hp since it has the 2.6 ratio.) I think the smoother mounts would be enough for me to try it and the remote oil reservoir may be nice. I know Matt has mentioned topping up on the water can be a hassle.

I think a good real world example of lower unit comparison is the etec 50 vs Honda 50 performance on a mac. Pretty much everyone reports better performance from the etec, and say its due to the etecs higher torque. The etec 50 has 45ft lbs of torque, the lowest of any 50 outboard produced. (torque for outboards through 2011 is on the epa website with the emissions data) The etec has the 2.67 gear ratio though, so 45ft/lbs x 2.67 ratio= 120ft/lbs at the prop. The Honda 50 is 47 ft/lbs torque but a 2.01 gear ratio = 94.5 at the prop, or about 20% less prop torque than the etec. Both are the same hp, but the lower ratio and larger foot of the etec can turn a 14” diameter prop vs the 11.8” on the Honda, which yields very noticeably real world results.

Wild speculation time

Prop efficiency goes down as the pitch goes down. So a 11 pitch would lose some hp due to slip inefficiencies and drag vs a 15 or 19 pitch. Some of the whaler guys claim lower pitch props can loose 10-15% efficiency, or around 10 useable hp on a 90. Basically they say on their heavier boat models the lower gear ratio allows a larger pitch and they get more total speed by utilizing more of the hp produced.

[EZ]

Since the pontoon series has a higher gear ratio than the standard version, it will swing a larger, high-thrust type prop at lower speed, which should be what you want for towing skiers and tubes. I would think it would be just the thing for the Mac power sailers, including for docking. Like the Big Foot outboards.

By "high-thrust" do you mean less prop pitch? Wouldn't that cause more prop walk when docking?

[Tomfoolery]

High-thrust as in large blades and/or large diameter, preferably both, but pitched to allow the engine to achieve rated speed.

Gotta be careful about gear ratios, as they're meaningless by themselves. An engine with a low(ish) rated speed and low reduction ratio can have the same prop speed as a fast engine and higher ratio.

The etec 90 pontoon is 90 hp (at the prop shaft) at 5000 rpm with a reduction ratio of 2.36:1 for a prop speed of 2119 rpm and shaft torque of 223 lb-ft.

The etec 90 (standard) is 90 hp at 5000 rpm with a reduction ratio of 2.0:1 for a prop speed of 2500 rpm and shaft torque of 189 lb-ft.

The Honda BF90 is 90 hp at 5800 rpm with a reduction ratio of 2.33:1 for a prop speed of 2489 rpm and shaft torque of 190 lb-ft, which is almost exactly what the standard etec 90 is, but with a much higher reduction ratio and faster rated engine speed.

The thing to look for when thinking about props is actual prop speed, not ratio, as that's just an intermediary between the engine and the prop. The propeller doesn't care how fast the engine is spinning, only how much torque is forcing it, how hard it has to push, and how fast it's supposed to move through the water.

Oh, and I never worry about prop walk on my boat, since the engine turn with the wheel. A boat with an inboard is another story altogether.

The above isn't addressed to anyone in particular, by the way. It's just something to keep in mind, and since I design large machinery with power transmission stuff all over the place, it's always on my mind.

[Starscream]

Here's the Etec marketing video: http://www.youtube.com/watch?v=9Dj1KEHsSiU

[Seapup]

It's just something to keep in mind, and since I design large machinery with power transmission stuff all over the place, it's always on my mind.

While branching the discussion off to torque I am curious how the torque over the rpm range comes into play with our boats. I notice some motors produce full torque much earlier than others. The merc 75 4 stroke produces full torque at only 2500rpm.

I pulled the following data from the EPA excel spreadsheet of the motors they test. I am guessing the torque numbers are without any gear manipulation, so should be a straightforward comparison. I thought it was interesting that pretty much all models were basically right on their hp ratings but torque can vary quite a bit. The yamaha F70 has way less torque than some of the other 70s and the 75 optimax has more torque than most 90s.



http://www.epa.gov/oms/certdata.htm#marineci

[Tomfoolery]

What's interesting about that spreadsheet is that some engines have a very wide power band, like the Optimax 75, which develops full power at 4000 rpm (73.9 hp), while rated power and speed is up at 5375 rpm (74.1 hp), while the Etec 50D develops full torque at full speed (49.6 hp at 5750 rpm). Doesn't say much about the shape of the torque curve, but it's interesting nonetheless.

Oh, and those torque figures are in newton-meters, and taken at the crankshaft, though possibly through the gear train to the prop shaft with the ratio then divided back out. Since outboard powered is determined at the prop shaft, those losses, small though they may be, I would think would be included in the EPA calcs.

I couldn't find the spreadsheet in the screen shot, though. I get a different spreadsheet from the EPA site in the link.

[csm]

Spoke with evinrude tech rep regarding stopping power that the PS touts, and my take away is that the lower gear ratio allows for higher pitch at a given prop diameter. That seems right in line with how I interpet Tomfoolery's comment about prop speed; more torque to turn a higher pitch prop without lugging. The rep siad the max dia is 14, but that they have a series specifically for pontoons, that range up to 13" dia. He said they are cupped to provide extra reverse thrust while still providing good fwd efficiency. Having better stopping/backing power along with reduced vibration just about have me sold. Thanks for all your input.

[Tomfoolery]

To be honest with you, my last boat had a 27 hp inboard with 2-blade folding prop, and I drove it for years. Reverse was always something to be very conscious of, as there wasn't much of it, and it took a lot of throttle to make it do much. Fast forward to my X with Honda BF50, and putting it in reverse was like tossing an anchor out the back. I don't worry about reverse even with my little 50.

I DO use a 4-blade high-thrust for pulling a wakeboard, but that's because I need all the forward thrust I can get at lower speeds. A big engine swinging a larger prop would obviously produce more thrust, but like any boat, you need to select the prop to suit the boat and the OB for the intended speed and engine rated speed.

Here's a link to the pontoon series props, which I ran across the other day when we started talking about this. Looks like they go up to just shy of 14" diameter.

http://shop.evinrude.com/products/59800 ... _13_Spline

[Boblee]

Spoke with evinrude tech rep regarding stopping power that the PS touts, and my take away is that the lower gear ratio allows for higher pitch at a given prop diameter. That seems right in line with how I interpet Tomfoolery's comment about prop speed; more torque to turn a higher pitch prop without lugging. The rep siad the max dia is 14, but that they have a series specifically for pontoons, that range up to 13" dia. He said they are cupped to provide extra reverse thrust while still providing good fwd efficiency. Having better stopping/backing power along with reduced vibration just about have me sold. Thanks for all your input.

Our 50hp etec came with the pontoon cupped prop but unfortunately when noticing it was looser than it should be? I tightened it up and went to find a new pin but getting old and forgetful lost track of what I was doing so two weeks ago when I put it into reverse after a 200m idle couldn't figure out why it wouldn't do anything , so it's now at the bottom of the Murray river.
That prop was great for when we were heavily loaded or condiditions were unfavourable (against tide or wind etc) but the spare (13.75 x13) which we used for two weeks is quiet good when unloaded (sort of ) and running with the current, what I did learn this trip was that running this prop at 2000 rpm gave us about 1.5 kph more than 1500 but cost us 2-2.5 k's per litre in economy but we still got about 8k's per litre so stuck to the 2000 rpm.
The real difference between the two props is that the pontoon prop could not get us up on plane and so was much slower but this would/should not be a problem with the 90hp and it would also have the advantage I believe of a slower idle spped if required.
The biggest problem with these boats is the range between about 8k and 25 kph or from where they are creating no wave through until they get on plane, in between those speeds they create more wave than a wakeboard boat with subsequent fuel losses.
Note too blow the cobwebs and unburnt oil out before pulling the boat out of the water the gps said 24.6 kph against the current (2 kph?) and that was towing a 3.6m aluminium dinghy aprox 200kg (loaded) but could only get 5000 rpm which with the dinghy off would be ok.
My advice for the op is to get the pontoon option (not sure what effects the mapping could have) and keep at least one spare prop for different applications and with the 90hp you would certanly have more, in my case we only use alloy props as logs and rocks can be a normal hazard for our usage.

[Seapup]

Here's a link to the pontoon series props, which I ran across the other day when we started talking about this. Looks like they go up to just shy of 14" diameter.

http://shop.evinrude.com/products/59800 ... _13_Spline

In the pic it does look like the pontoon prop has a larger/rounder ear. It would be nice to see one side by side with the standard prop, may be the ticket.

I ran a solas 4 blade on my Honda that worked pretty well (still have it in the garage if someone wants it) It had fairly large rounded ears. The larger solas 4 blade for the 90 has more traditional ears, I was not overly impressed with it.

I couldn't find the spreadsheet in the screen shot, though. I get a different spreadsheet from the EPA site in the link.

The screenshot is of motors commonly used on macs off the epa charts I pulled awile back when I was shopping, you are right the torque is Nm, torque is on the models tab at the bottom.