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05-01-2010, 11:49
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#1
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Registered User
Join Date: May 2009
Location: Grenada
Boat: Shorebro,Royal 33 - Aloisius
Posts: 1,059
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Yamaha Acceleration Problem
So I have fixed one problem on the outboard, now for the next.
The motor starts very well, will go into forward and drive the dinghy. If I go to full throttle, it will accelerate out of control. If I stay in half speed all is good.
Could this be a shear pin that is broken? Also I went to the dealer and looked at a pin and I am use to a shear pin that is not entirely straight, an indentation where it is designed to break. (Snow blowers)
Confession:
I have recently had the forward, reverse, neutral control arm replaced, it broke off after the dinghy got washed under a pier. I also have touched bottom a couple of times trying to cut a point a little too close.
I have a Yamaha 5hp, 2001, model 5MSHZ.
Any suggestions?
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05-01-2010, 11:57
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#2
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Moderator Emeritus
Join Date: Sep 2007
Location: Eastern Tennessee
Boat: Research vessel for a university, retired now.
Posts: 10,406
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Are you saying it feels like the engine is accelerating without a subsequent increase in propeller RPM?
If so, the rubber donut inside the propeller hub may be slipping. It is designed to slip if your propeller ever hits something. It is designed to protect the engine and drive train. The only solution I know of is to replace the propeller. The propeller goes over a splined shaft and is held in place by a nut that is prevented from turning by a bendable nut cap or a shear pin. The nut either works or it does not.
__________________
David
Life begins where land ends.
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05-01-2010, 12:00
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#3
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Registered User
Join Date: May 2009
Location: Grenada
Boat: Shorebro,Royal 33 - Aloisius
Posts: 1,059
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Yes, after about accelerating half way, it will rev VEY high if I increase the gas and no increase in speed.
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05-01-2010, 12:03
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#4
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Registered User
Join Date: May 2009
Location: Grenada
Boat: Shorebro,Royal 33 - Aloisius
Posts: 1,059
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On this engine, does the cotter pin you see holding the nut to the prop work like the shear pin?
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05-01-2010, 12:06
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#5
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Registered User
Join Date: Dec 2009
Location: Kingston / Thousand Islands, Ontario
Boat: C&C 35 Mk.II
Posts: 343
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That does sound like a slipping hub, landonshaw. I don't know of any recent engines that use a shear pin on the shaft (a cotter pin, of course, is still standard)- the rubber hub is the standard now, and it behaves very much as you describe when it starts to fail. Ventilation (sucking in air from the surface) or cavitation (vacuum bubbles on the trailing face of the blades- rare on a motor so small) can also cause similar symptoms, but if either of these were at fault, you'd have noticed when the engine was first installed.
__________________
Matt Marsh
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05-01-2010, 12:07
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#6
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Registered User
Join Date: May 2005
Location: Cruising Greece
Boat: Cat in the med & Trawler in Florida
Posts: 2,323
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I would bet you have a rubber mounted prop, and its slipping with the increase in power-what eles could it be??
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05-01-2010, 12:08
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#7
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Moderator Emeritus
Join Date: Sep 2007
Location: Eastern Tennessee
Boat: Research vessel for a university, retired now.
Posts: 10,406
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I think your prop is slipping around the rubber donut. The way to test this is to lock your crank shaft in place with your engine in gear. Then put a good sized pipe wrench on the prop itself and see how easily it turns. If it turns real easy then you have found the problem. Don't go overboard with the torque..you don't want to break anything.
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David
Life begins where land ends.
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05-01-2010, 13:07
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#8
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Registered User
Join Date: Nov 2008
Location: West Coast, BC , Canada
Boat: Cascade
Posts: 595
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Are you planing
Quote:
Originally Posted by landonshaw
Yes, after about accelerating half way, it will rev VEY high if I increase the gas and no increase in speed.
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Are you planing? Or just pushing water at full throttle.
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Go outside and PLAY!
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05-01-2010, 17:25
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#9
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Registered User
Join Date: May 2009
Location: Grenada
Boat: Shorebro,Royal 33 - Aloisius
Posts: 1,059
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05-01-2010, 17:28
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#10
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Registered User
Join Date: May 2009
Location: Grenada
Boat: Shorebro,Royal 33 - Aloisius
Posts: 1,059
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Are you able to replace the rubber donut or is it a new prop?
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06-01-2010, 10:13
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#11
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Registered User
Join Date: Nov 2008
Location: West Coast, BC , Canada
Boat: Cascade
Posts: 595
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Let me understand
Quote:
Originally Posted by landonshaw
I am pushing water.
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Have you been able to plane?
Its 5hp, How big is the boat? I have a 4 hp 2 stroke Merc. I can only plane with one in the boat. If I push it any further when loaded I only push water but don't plane.
If your just reaching hull speed you wont be able to plane and wont go any faster with full throttle?
If you were planing before with the same load then you may have a problem.
S
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06-01-2010, 11:40
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#12
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Registered User
Join Date: Apr 2008
Location: On the boat - Carib, Chesapeake
Boat: 58 Taswell AS
Posts: 1,139
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Unfortunately, you must replace the entire prop but they are not expensive. The dealer should be able to sell you the prop that is consistent with your application.
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08-01-2010, 15:01
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#13
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Registered User
Join Date: May 2009
Location: Grenada
Boat: Shorebro,Royal 33 - Aloisius
Posts: 1,059
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I purchased a new prop and the manual calls for 17 lb torque. Without a torque wrench I estimate that is finger tight and then tighten until the cotter pin lines up. Any suggestions?
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08-01-2010, 17:35
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#14
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Registered User
Join Date: Nov 2005
Location: Bradenton FL
Boat: Med Yachts 62 Trawler
Posts: 1,180
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Quote:
Originally Posted by landonshaw
I purchased a new prop and the manual calls for 17 lb torque. Without a torque wrench I estimate that is finger tight and then tighten until the cotter pin lines up. Any suggestions?
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Sounds exactly right to me. Let us know the result with your new prop!
__________________
Mark
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08-01-2010, 17:43
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#15
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Moderator Emeritus
Join Date: Sep 2007
Location: Eastern Tennessee
Boat: Research vessel for a university, retired now.
Posts: 10,406
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Quote:
Originally Posted by landonshaw
I purchased a new prop and the manual calls for 17 lb torque. Without a torque wrench I estimate that is finger tight and then tighten until the cotter pin lines up. Any suggestions?
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Or make your own torque wrench by hanging 17 pounds of weight on a line 12 inches out from the center of the nut.
__________________
David
Life begins where land ends.
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