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As I do quite a bit of shallow water (3-8ft.) high-speed trolling (+/- 5mph) and had the habit of sometimes hitting rocks, I thought it might be a good adea to carry a spare prop and need your advice.

Current setup:
1991 Outrage 17
2005 E-Tec 90hp on a 4" aluminum setback manual bracket (AV plate is 2,25 in. above the lowest point of the keel)
Prop is an OMC SS Viper 13 7/8 x 17 (part #763930)

Alone (220lbs) with a full tank of gas (34 gallons), it rev a bit too high at WOT (5600rpm, 39mph), the optimum range being 5000-5200rpm, but it handle really well without never losing grip. Hole shot is phenomenal, it cruise nicely and stay on plane at 20mph but there's a tendancy to porpoise at WOT when fully trimmed up, wich I hope to take care of by moving the batteries into the console. With 2 or 3 people aboard and loaded, the WOT rpm is right around 5200-5300.

As I need a second prop, am I better to buy a similar one (that one http://www.boats.net/parts/detail/pro...63930.html seems priced right) or should I look for something else with a higher pitch to bring down my rpm? BRP doesn't make the Viper in even pitch number but it seems that a 18 would be perfect in that case...

Any recommendations?

Thanks.

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39 MPH at 5600 RPM through a 2:1 gear ratio with a 17" pitch prop is over 13 percent calculated propeller slip. That is quite high for the BRP Viper model.

Switching to the 19" Viper will, ceteris paribus, drop your RPM down to just over 5000 RPM, within the optimal RPM range.

Those Boats.net Viper prices are VERY good. Still, you could buy a 17" Stieltto Advantage for a little less and it would probably be a better prop for you.

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Will the Stiletto 17 turn the same rpm than the Viper or lower? At 5300 alone, 5000 loaded, I'd be happy...

I sometimes wonder if the engine isn't mounted too high (it's been set-up by the previous owner), as there's no real gain in speed for the last 10% or so of throttle advance. At 5100rpm, it already reach 38mph and if I push it all the way, it barely gain another mph and start to rock back and forth. It is like 4 holes up, i.e. higher that it can be if bolted to the transom.

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Tom, you made me look up ceteris paribus.....

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I actually think your motor is mounted too low for being 4" set back. I would suggest atleast moving it up another 3/4" to 3" and adjust it higher from that point. Your cavitation plate is probably still under water on plane where you have it set. I dont have experience with he viper props so i dont know how high they will tolerate. If you had a stiletto prop, I wouldn't be surprised if you could raise it 3.5 to 3.75 above the keel

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I have a 19" Viper off of my 150 Evinrude, I needed a 17", and it works much better. I'll sell it for $165 shipped to you. You can email if you want it rockfish54@gmail.com I can take some pics if you want to see it

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No, a 17" Stiletto Advantage will not turn the same RPM as a 17" Viper. It will turn quite a bit less.

This is a good example of how you must consider the model of propeller not just the pitch. There will be a BIG difference between these two models of propeller.

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I sorry I don't think my Viper will fit a 115hp, I'm sure someone here will know for sure.

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It won't fit a 90 either because the 90 HP E-TEC uses an Intermediate size gearcase while a 150 HP motor uses a Large gearcase

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I haven't called Dan's but from the checkout options on his website, it doesn't look like he ship to Canada. Anybody know if he does? If not, it seems I'm out of luck for a $250 Stiletto...

In another vein, in using the search function, I haven't seen much data for the Outrage I-17 with a 90hp, the few of them being with a 115hp. A lot of 90hp E-Tec combination with the Montauk but the Outrage is a different boat...

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I finally got a slightly used Stiletto 17 w/OMC hub for $200 off eBay. Will try it and report back as soon as water stops being that hard...

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Very good. eBay is an excellent source for inexpensive used propellers. I have bought many, many propellers off of eBay.

Dan's Discount Props, like many vendors, may ship to Canada for the added expense. When I ship a prop into Canada, I usually just have the factory send the prop to me, then I inspect it, and turn around and mail via the US Postal Service Priority mail. This adds a small cost.

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Update: had a chance to but the boat in the water today to check if everything's right before the fishing opener.

Alone in the boat (220lbs), with a full (32 gal = 200lbs) tank of gas, a 55lbs kicker, two batteries (gr. 24 & 31= 120lbs) in the console and some tools, spare prop, anchor (60lbs), I manage to reach 40mph @ 5100rpm with the Stiletto 17p.

The porpoising is also eliminated (could be caused by the batteries moved to the console) and I noticed I could trim a lot higher. Was able to stay on plane at 23mph @ 3200rpm.

There's not much Outrage 17 rigged with 90hp, so comparisons are hard to made, but so far I'm really pleased with this setup. The boat being a bit heavier than a Montauk and having a deeper V, with the added weight of the fuel tank and kicker, I'm happy I could reach 40mph.

That prop having so much grip, I even think of raising the engine all the way up on the bracket. I measure it carefully with a 2"x4" on the bottom of the keel and the AV plate is now 2" higher than the lowest point. If I mount it all the way up (2 holes left), that will give 1.5" more, putting it 3.5" higher. Does it seems too much?
http://www.myfishingpictures.com/data...00/197.jpg

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40 MPH with that load is pretty damn good with only 90 HP.

With the setback, no I don't think moving up another 1-1/2" would be too much. Try it and see.

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Moved the engine all the way up on the bracket (2 more holes, now AV plate is 3.5 in. above keel) and didn't notice much difference. Still top at 40mph @ 5100rpm, the only difference being the trim range that is reduced before porpoisong occur.

Before, from fully trimmed in, I could could go almost halfway up on the trim gauge before it start porpoising and, if I continue, sucking air. Now I only need to trim it up till it reach the first quarter before that happened.

I guess that about all I can get with that engine/hull combination. I'm still amazed to reach that with ony 75% of the max hp, thoses hull are really efficient...

(tests have been done with the Stiletto 17p, I'm not sure the Viper would have been able to hold his grip mounted that high...)