Confucius Says: - FryingPanTower.Com

Posted: Wed Mar 10, 2010 6:22 am Post subject: I need a some opions!!

My 20 ft. neptune is powered by a suzuki115 four stroke.To me it seems like I should be running faster than my speedodometer says. it says 25 mph. at 4800 rpms.What shouldmy rpms be for a long ride for top speed? I always thought 5200 rpms were a good crusing speed,but maybe thats on a 2 stroke. My motor wants to cut back at that rpm if running more than 3-4 minutes. Any suggestions on how to get more speed, maybe wrong blade pitch, motor to low,maybe motor just not big enough. Anybody who really knows this stuff, would you like to take a ride to help tell me if this is the best it is gonna get or there is ways to improve . I live around Topsail and usually put in at Surf City bridge. Thanks for any help .. Rolling Eyes

Posted: Wed Mar 10, 2010 6:35 am Post subject:

Have you checked your speed on a GPS?...If I were you I would check a bounce speed readings between your speedometer and a GPS. And then take it from there, before you going doing any changes or spending $$. I have a 19 foot skiff (DLV) with a 4 stroke 90 Suz (4 Blade prop) and at 4500 rpm I cruise a very confortable 25 mph on and about 22 on speedometer, both the 90 and 115 Suz are built on the same block.
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Hector
Harrells, NC
198 DLV
www.carolinaskiffowner.com
www.carolinakingfish.com

Ol'Salt Joined: Apr 03, 2007 Posts: 476

Most boats cruise at 4000-4500 for best fuel economy. I think your speed is right. Boat may be a little underpowered. I have a buddy with a 19 MayCraft with a 140 Suz 4 stroker and cruise at about 25. Triming your motor up will help you gain speed.
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Tony Pavone
High School Mathematics Teacher
Y-Not Fishing Team
23 Key West (2) 140 Suzuki 4 Strokes

Crystal Coast Interiors
www.ccinteriors.us

Posted: Wed Mar 10, 2010 9:07 am Post subject:

yeah i would check it on a gps or get a buddy to run beside you to check speed. You probably would get better mpg if you stayed under or around 4000prm. Do the cheapest fixes first!!!!!

1. Check on gps
2. trim motors up

Then you might have to look a props but that can get expensive very fast
I agree with Tony you might be doing the best you can with 115hp. It will get the job done but might be underpowered if you want to run fast.
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Three Buoys Fishing Team
26' Regulator

Posted: Wed Mar 10, 2010 9:13 am Post subject:

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Three Buoys Fishing Team
26' Regulator

Posted: Wed Mar 10, 2010 9:37 am Post subject:

..I might be offa my rocker, but it sounds under-powered to me. A 115 4 stroke on a 20' Neptune.? What's the rig rated for.? Are you maxing out rated RPM's with the rig all trimmed up proper.? Boats can be different, but with a 20' boat I'm usually lookin for it to have a 150HP or so on it, depending. As I remember the Neptunes have a decent bit of "V" on'em.. Cool

d:^) Schneeky..

Posted: Wed Mar 10, 2010 9:42 am Post subject:

Underpowered. I have a 115 yami on my 17 Edgewater and I wish even it were rated for more. However, you can't beat the fuel economy

Posted: Wed Mar 10, 2010 6:32 pm Post subject:

Thanks guys , I was figuring that I was getting what the boat could do with the 115. Just wanting to see if most of you agreed, before spending alot of money. Just bought the boat a few months ago and love the fuel economy.Thanks for the opions and help.

Ol'Salt Joined: Jul 29, 2008 Posts: 197

3200 - 3800 is optimal crusing RPM's.... With that being said is looks like you new prop with a different pitch or your speedometer is just off

Posted: Wed Mar 10, 2010 7:22 pm Post subject:

I have the 115 Suzuki on a 218 dlv. WOT is about 5500rpms and 47 mph according to my gps. 4000 rpm gets me about 30 mph.
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Captain Mick
2008
218 DLV

Newbie Joined: Dec 14, 2006 Posts: 4

Fishthis..I have a 98 20 neptune with a 150 hp, the boat is rated up to a 175 hp. I think you are underpowered for the speed you want. With that 150 I am scared to open it up all the way (too fast for my tastes) though it cruises very nicely.

Posted: Wed Mar 10, 2010 9:01 pm Post subject:

I have a 98 23' neptune with a 200.. Max speed is in the high 40's, mid 20's cruising. Dont know if that helps at all?
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2009 14\' Voyager Jonboat
2009 9.8 Nissan Marine 4 stroke

Posted: Thu Mar 11, 2010 6:33 am Post subject:

My boat is rated for a 150 max. I am quessing the boat is just to heavy and carries 64 galons of gas. You would think I should be able to run 30 though.

Posted: Thu Mar 11, 2010 6:43 am Post subject:

..Have you weighed the boat to see how that compares with what the mfg says it should weigh.? I don't remember what the construction is on a Neptune.

Posted: Thu Mar 11, 2010 4:55 pm Post subject:

Love the DLV. It does a good job running Buzzard Bay and we have put a ton of fish in it,
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Captain Mick
2008
218 DLV

Posted: Thu Mar 11, 2010 6:19 pm Post subject:

My old 18' Parker had a 200 Mercury EFI...And it would do a little over 60...May have been over-powered? Sold it before I got killed.

Not sure with many things about a Neptune, but I would say low on power if you are looking to get speed. My dad has a 20' Cape Fisherman that had a 150 Merc on it, ran about 40 wide open, he replaced it with a 200 Opti as he wanted more power when the whole family is aboard.

5200 is very high for a cruise, I usually run 4-4200, most of my engines topped out at 5400-5800.
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