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Prop Help, need 500 more RPM

Old 09-24-2019, 02:55 PM
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Default Prop Help, need 500 more RPM

On my 230 HydraSport Seahorse, I'm running a 200 HO G1 Etec, spinning a 14 1/4 X 19 Stainless Steel Renegade 4 blade, which I suspect is just starting to spin the hub. (See the shark thread for hilarity.)

At wide open throttle on all loads I'm at 5000RPM, which is 500 RPM short of the evinrude recommended 5500RPM. I'd like to find a new four blade that gets me into the correct RPM range.

Any suggestions?
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Old 09-24-2019, 09:28 PM
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Is it an issue to be slightly over propped (500 RPM)?
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Old 09-24-2019, 09:46 PM
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General rule is 200+ rpm with every inch of pitch dropped. But way more to it than that. Smaller diameter can raise rpms. Two men on here, Ken and Tom have forgotten more about props than we will ever know. One of them can help you.
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Old 09-25-2019, 06:55 AM
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Pick your poison.

lower pitch, higher rpm, better hole shot and planing control..........lower fuel economy, lower top end speed...most likely

If dont run wot.....forget about top end
at least in small boats...offshore is 18-30mph, not 45.
Fuel economy at cruise is most important imo.

In college i took roommate out on dads boat to fish. Made same run id done 50x before w/o problem. Didnt pay attention to fuel due to this. Calm day....showed off....ran WOT most of way. Had fun, caught lots of fish.

We had to be towed in.....ran out of gas.

Last edited by mbb; 09-25-2019 at 07:04 AM.
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Old 09-25-2019, 07:05 AM
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propping correctly should result in improved fuel economy!
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Old 09-25-2019, 07:11 AM
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mbb
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Originally Posted by Rolandt03 View Post
propping correctly should result in improved fuel economy!
Not always. Lower pitch or 4 blade has more drag than higher pitch. The higher top end of higher pitch at WOT shows you this...even at little lower rpm...ie your more efficient at top end...theres a balancing act between power, slippage, drag. If your close, your power already is basically maxed on top of curve. Not much to gain, but there is something to lose. That something can be 5 mph from top end.

We like to prop at max motor rpm to reduce load on motor per revolution. Ie....longer life

This isnt necessarilly synonymous with achieving peak prop efficiency at a given speed.

Last edited by mbb; 09-25-2019 at 07:42 AM.
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Old 09-25-2019, 08:36 AM
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How fast does the boat go now at WOT (5000 RPM)?
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Old 09-25-2019, 04:59 PM
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I'm learning a ton, thanks guys.

About 40knts, WOT inside where it's calm. Called a prop guy that said the range was 4800 to 5800 RPM.

If he's correct it looks like I'm well within range.
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Old 09-25-2019, 05:11 PM
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The G1 E-Tec 200 H.O. has a 4800-5800 WOT RPM range but the Optimal Range, per BRP, is 5500-5700 RPM. You should target that.

The first thing that comes to mind is a 17” Mercury Revolution 4 / Quicksilver Q4 or a PowerTech! OFS4 if you want a four blade, but I think the question really should be: What are your performance goals?
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Old 09-25-2019, 05:31 PM
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We ran a seahorse 2350 HS for 3 plus years. It had a Verado 275HP on it and it loved running at 4500 Rpm, cruising 28 Mph with a Rev4 x 17pitch prop. Also ran a 3 blade mirage II 15"x15P with a little cup added and cruised a hair quicker and a hair better mileage but not enough to really notice on a daily basis. Now running a HS 2390 with a 250 HP Etec, running same 3 blade as above, plus Cyclone 15x15, and a Cyclone 15x17 4 blade. Pretty close in cruise, top speed, and fuel usage, opting for the 15x15p for great hole shot among other things. As far as the prop guy goes telling you your in the Rpm range, I've checked Etec performance numbers and I would try to get WOT numbers up to 5800 or so. These engines like to rev and anything between 4500-5500 Rpm, my fuel usage is almost exactly the same. 5000 Rpm at WOT is loading up your engine and doing more damage than good.
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Old 09-25-2019, 05:55 PM
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While you're experimenting with the prop, ensure your motor is mounted in the appropriate hole height for said prop.
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Old 09-26-2019, 05:30 AM
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That boat may not like a 4-blade / borrow someone's 3- blade and start from there .
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Old 09-26-2019, 10:38 AM
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Originally Posted by eds500 View Post
While you're experimenting with the prop, ensure your motor is mounted in the appropriate hole height for said prop.
This comment should always be included by the person with the prop issue or the 1st person to respond. Lots of boats mounted with the prop buried.
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Old 09-26-2019, 10:42 AM
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Originally Posted by rrhyne View Post
Is it an issue to be slightly over propped (500 RPM)?
Same as lugging an automobile engine by having it in the wrong gear. Bad for the engine across the entire RPM range.
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Old 09-27-2019, 07:46 AM
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Good morning rhyme. As several others have posted on here, check your engine height first. On the Seahorse we owned, we moved the engine up I believe 2 holes from where it was mounted by previous owner and with that and prop testing, we dramatically changed both fuel burn and speed. That boat was bought used without ever meeting the previous owner as he was transferred for his job from Long Island to Florida. When I did speak to him, he has acquired the boat in a business trade and didn't really know too much about it. The HS 2390 was purchased from the owner that had it repowered by a professional local dealer and that boat was a dog during the sea trial, but I had read many reports about that boat/engine combo, and had good feelings about what I could expect from fixing the errors I saw. Engine was lifted up as high as possible. This alone made for huge improvements, but adding the prop testing I tried, the boat runs right where some of the others on here with the same boat/engine combo have stated. If anything, I think our results are on the higher side of others reports in both cruising speed and fuel usage. Only my WOT speed seems to be lower than I have read about but have a feeling that I run boat heavy as compared to others running lighter, with the wind and tide behind them, etc. like I said earlier, spin that Etec up some. My Etec reaches posted HP ratings at 5500 Rpm and yours is probably the same. Any RPMs less than that and your trying to move your boat with less than posted HP.
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