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#11183884 - 10/24/15 08:35 PM Puzzling mid rpm issue
Garvin Offline
Angler

Registered: 11/11/14
Posts: 342
Loc: Texas
I recently bought a 2003 Nitro 882 NX with a 115 Mariner 2-stroke. It is propped with a 3-blade Laser II 22p. The boat is an 18 footer, and I realize it is under-powered, but that's the motor that came with it and I don't currently have the option to upgrade. The boat came with a Stingray hydrofoil, but having had to recently replace the lower unit, I have not yet mounted it back on but the problem I'm having occurs with or without it.
In a nutshell, slow speed good, fast speed good, midrange speed, no good.
I can run it full throttle from a dead stop and it will plane out.
I can also run it slow and it will push along at 6-7 mph just fine.
However, If it try to throttle to midrange, around 2500 - 3000 rpm, it does this weird thing where the bow will start to rise, then the the prop just starts churning and boiling real hard, but won't plane out. It does this no matter if I start with it trimmed up, down, or in the middle. I end up either backing off or pushing it to full. The first thing I wondered is if I have a spun prop, but it doesn't do it at the high end of the rpm range, just the mids. I can't seem to find this same issue on the Google machine, so I'm wondering if anyone here can postulate on what might be happening.

Secondly, I have been wondering if a 22p is too much prop for this rig. I have been kicking around the idea of switching to a 4-blade prop and pitching down a couple inches to give me a little more low end torque. I don't know enough about prop physics to make a completely informed decision, though. Only what I've read on the internet.

Thanks, and hope everyone's staying dry this weekend.
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#11184215 - 10/24/15 10:32 PM Re: Puzzling mid rpm issue [Re: Garvin]
Josh@SCP Offline
Angler

Registered: 04/27/07
Posts: 385
Loc: Winnsboro TX
I would not switch to a 4 blade on your rig. You most likely have the prop vented to much or the cup is worn down. Both issues can cause your blow out problem.

What RPM are you turning at wide open throttle trimmed up running as fast as the boat will go?
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#11184271 - 10/24/15 11:29 PM Re: Puzzling mid rpm issue [Re: Josh@SCP]
Garvin Offline
Angler

Registered: 11/11/14
Posts: 342
Loc: Texas
Originally Posted By: Josh@SCP
I would not switch to a 4 blade on your rig. You most likely have the prop vented to much or the cup is worn down. Both issues can cause your blow out problem.

What RPM are you turning at wide open throttle trimmed up running as fast as the boat will go?


Since I'm breaking in a new SEI lower, I can't go WOT for 4 more hours of operation. But prior to replacing it, I didn't bother to mark top RPM's. As soon as I can go full throttle, I'll take note of the rpms. How would you approach the prop being too vented? Should I try a smaller vent plug? And if the cup is worn down, would that call for a new prop? Thanks very much.
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#11184487 - 10/25/15 08:45 AM Re: Puzzling mid rpm issue [Re: Garvin]
SteezMacQueen Online   happy
TFF Team Angler

Registered: 11/02/14
Posts: 3022
Loc: Red Oak, Galveston, and Pagosa...
Not enough power. I have the same issue with my old Nitro. It gets on pad fast. Rides great. It just struggles in getting an old water logged hull up and out with mid throttle. Nail it! And it goes great. Cruise out of the water and it takes 30-40 seconds to nose over. I have the same generic sting ray $50 foil. The foil helps a LOT. it looks stupid.... But helps. I have anRapture prop (same as an Apollo). It is a great prop. My RPM is about 5300 on pad. My boat is slow. GPS speed is right around 43-45 depending on load.
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#11184699 - 10/25/15 11:01 AM Re: Puzzling mid rpm issue [Re: SteezMacQueen]
Garvin Offline
Angler

Registered: 11/11/14
Posts: 342
Loc: Texas
Originally Posted By: SteezMacQueen
Not enough power. I have the same issue with my old Nitro. It gets on pad fast. Rides great. It just struggles in getting an old water logged hull up and out with mid throttle. Nail it! And it goes great. Cruise out of the water and it takes 30-40 seconds to nose over. I have the same generic sting ray $50 foil. The foil helps a LOT. it looks stupid.... But helps. I have anRapture prop (same as an Apollo). It is a great prop. My RPM is about 5300 on pad. My boat is slow. GPS speed is right around 43-45 depending on load.


Are you running a 19 or 21 pitch on your prop?
Is your rig about the same size/hp as mine?


Edited by Garvin (10/25/15 11:36 AM)
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#11184992 - 10/25/15 01:48 PM Re: Puzzling mid rpm issue [Re: Garvin]
Garvin Offline
Angler

Registered: 11/11/14
Posts: 342
Loc: Texas
It looks like I'm not the only person with this issue. Here's a clip from the transomtalk forum from a post made in 2004 (not directed to me):

"I have the same setup...882 with 115 2-stroke. I am running a 22P LaserII. While this is not the greatest prop it planes very well when running light but it does suffer with a full load of gas and livewell especially if it is hot and humid. I hit 5200RPM's on the top end and consistently get 49mph on the GPS. I have found that to get the best results I have to not be idling at all and just punch it...if you ease into it with the two stage 2-strokes like the 115 and 125 you will bog down."

That describes my situation with my boat. The part in italics especially. That's why I was considering a 4 blade to get some more midrange usage. I don't care about losing a couple mph on the top end if I can get more out of the mids.

Josh@SCP, could you please offer more on why a 4 blade would not be recommended? Thanks again.
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Just ONCE I'd like for someone to call me "Sir" without adding, "please stop making a scene."

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#11186322 - 10/25/15 08:58 PM Re: Puzzling mid rpm issue [Re: Garvin]
gary purdy Offline
TFF Guru

Registered: 05/24/03
Posts: 10509
Loc: Littlefield Tx & Lake A. H. US...
I noticed all of these outboard`s have the same accelerator pump and it needs to be set right or you will have this problem. I just worked on a 2006 Nitro with a 115 Optimax and it runs well with a 20p.
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#11188362 - 10/26/15 08:17 PM Re: Puzzling mid rpm issue [Re: Garvin]
Josh@SCP Offline
Angler

Registered: 04/27/07
Posts: 385
Loc: Winnsboro TX
Give me a call at the shop tomorrow. Its the number in my signature.
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#11192799 - 10/28/15 08:52 PM Re: Puzzling mid rpm issue [Re: Garvin]
Chris B Online   content
TFF Celebrity

Registered: 05/02/03
Posts: 5730
Loc: Prosper, TX
What is your experience driving bass boats? You should always be taking off with the motor trimmed all the way down. There is nothing wrong with going full throttle until the boat planes off. Then you adjust the trim for the speed you want to go. And most bass boats wont run between 8 and 20 mph. Your either idling or on plane doing 25.
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#11193238 - 10/29/15 07:48 AM Re: Puzzling mid rpm issue [Re: Chris B]
Garvin Offline
Angler

Registered: 11/11/14
Posts: 342
Loc: Texas
Originally Posted By: Chris B
What is your experience driving bass boats? You should always be taking off with the motor trimmed all the way down. There is nothing wrong with going full throttle until the boat planes off. Then you adjust the trim for the speed you want to go. And most bass boats wont run between 8 and 20 mph. Your either idling or on plane doing 25.


Thanks, this is actually my first true bass boat. Prior to this, I had an aluminum boat with a 25hp motor, and while it had console steering, remote shift/throttle, and power trim, it of course handled much differently than my current boat. I could plane out with my old boat without having to go wide open then backing down. I'm starting to realize that with the size outboard I have on my bass boat now, I have to use all the power it has to get on plane, then throttle down to a midrange speed.
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