#896090 - 05/27/14 01:22 PM
Pulling flywheel on 1997 Merc 40hp
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Poon it! Poon it! Poon it!
Registered: 08/08/06
Posts: 1721
Loc: Yarrow Point
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Anyone here got the skills (or a person you'd recommend I talk to?) to help me through this? Here's the deal:
PROJECT: 1997 Mercury 40hp (2-stroke/4-cylinder)
SITUATION: Starts/runs well but after running a while (sometimes an hour or more) it begins to lose power at full throttle... It *feels* like a situation where you've forgotten to open the vent on your fuel tank, because it happens fairly dramatically, you're cruising at 4000 RPM, then it just drops down to 1500...
I'm suspecting an ignition issue, going to go through the coils tonight (they look good by inspection)... Next step is to look at the magnets/Stator under the flywheel...
I've got access to an impact wrench, but don't have a flywheel puller/etc... Can I go the next step here myself/with modest investment in tools? Or am I out of my depth? I have the Seloc guide and am reasonably handy, but am inexperienced so looking for sage wisdom!
Thx,
B
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The charm of fishing is that it is the pursuit of what is elusive but attainable, a perpetual series of occasions for hope. -John Buchan
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#896172 - 05/28/14 05:56 PM
Re: Pulling flywheel on 1997 Merc 40hp
[Re: IrishRogue]
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River Nutrients
Registered: 11/05/04
Posts: 2713
Loc: right place/wrong time
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Perhaps a little more troubleshooting might be in order before you consider removing the flywheel. I like to perform all possible minor troubleshooting before ripping into things to deeply.
Is your tank built in, or remote? If it is built in consider that many built in tanks have screen on the pickup tube which can clog. If you are using remote tanks have you tried changing tanks when the symptoms occur? Does it have an inline fuel filter? Many engines have a inline fuel filter under the hood, and some installations have a canister style filter mounted in the outboard well or, on the inside of the transom.
Good luck
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"The best argument against democracy is a five-minute conversation with the average voter." Winston Churchill
"So it goes." Kurt Vonnegut jr.
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#896174 - 05/28/14 06:00 PM
Re: Pulling flywheel on 1997 Merc 40hp
[Re: blackmouth]
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The Rainman
Registered: 03/05/01
Posts: 2347
Loc: elma washington
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try a different hose if you are using one. I had a hose with an inner liner that would suck shut slowly.
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don't push the river it flows by itself Don't argue with an idiot; people watching may not be able to tell the difference. FREE PARKER DEATH TO RATS
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#896184 - 05/28/14 08:31 PM
Re: Pulling flywheel on 1997 Merc 40hp
[Re: DBAppraiser]
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Spawner
Registered: 01/22/06
Posts: 925
Loc: tacoma
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I would agree 100% with those who say try everything else first. Pulling off a fly wheel without knowing why or how sounds like a good way to end up with an engine laying around for parts. Outboards either run or they dont assuming fuel and basic stuff is taken care of.
Been there done that.
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#896213 - 05/29/14 10:10 AM
Re: Pulling flywheel on 1997 Merc 40hp
[Re: milt roe]
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Juvenile at Sea
Registered: 03/28/13
Posts: 118
Loc: Lynnwood,WA
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It sounds like it is going into "safe mode". My Yamaha was doing that. It ended up being the oil sensor. Might want to check those things first. There is a way to bypass those sensors. Contact a mechanic and ask about it. Does your alarm work?
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Good shocks and four wheel drive!
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#896223 - 05/29/14 12:27 PM
Re: Pulling flywheel on 1997 Merc 40hp
[Re: WABOWMAN]
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Poon it! Poon it! Poon it!
Registered: 08/08/06
Posts: 1721
Loc: Yarrow Point
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All the feedback here is really helpful/appreciated... The basics of the fuel system seem correct (new filters/etc) but I appreciate the "try igintion last" advice... I'll work thru that with more care... If I can reproduce the fault (which is not simple, I generally have to be on the water, it's hard to reproduce in the driveway) -- what suggestions do y'all have for testing the "fuel" theory -- squeeze bulb and see if that changes things? Obviously if I can get it to happen, then do a 'test' to indicate if we're fuel or ignition, i'll have made progress. I'll read up on testing the alarm too, "safe mode" is an interesting theory as well! FWIW, my endeavor into the ignition system was inspired by THIS THREAD
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The charm of fishing is that it is the pursuit of what is elusive but attainable, a perpetual series of occasions for hope. -John Buchan
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#896229 - 05/29/14 12:55 PM
Re: Pulling flywheel on 1997 Merc 40hp
[Re: AP a.k.a. Kaiser D]
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Parr
Registered: 07/04/01
Posts: 73
Loc: Okanogan County
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my thought is (I am an old small engine mechanic) I suspect a fuel problem. Clean all the screens especially the one at the fuel pump and is there one in line? If so then replace it. Then check fuel tank and look at pickup tube in the tank. Does the fuel bulb go flat when running? if so then check the venting on the tank.
Ignition is electronic (99% sure of this) it works or it don't but if it gets hot it will shut down and when cooled it will allow a restart. Flywheel key could be possibly sheared or partially even, do not know if you can pull flywheel nut and inspect or if it is a 1/2 moon key and is hidden. Than can also somewhat do the symptom your having.
Just my $000.02 worth GFN
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#896262 - 05/29/14 11:10 PM
Re: Pulling flywheel on 1997 Merc 40hp
[Re: AP a.k.a. Kaiser D]
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Smolt
Registered: 01/06/01
Posts: 91
Loc: Aberdeen Wa
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I think u have a bad coil, u have one for each plug one of them is bad
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#896286 - 05/30/14 01:00 PM
Re: Pulling flywheel on 1997 Merc 40hp
[Re: womperman]
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Juvenile at Sea
Registered: 03/28/13
Posts: 118
Loc: Lynnwood,WA
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I think u have a bad coil, u have one for each plug one of them is bad That is a reasonable answer! Run it till it happens. Then with a simple light cruciut tester probe the coil wires. Find which one isn't working. Then switch the power feeds to that coil. If the dead coil moves it's your chi box. If it stays the same it's the coil. I've had a box do that.once it's warm it would shut down a cyl. Like a coil will do.
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Good shocks and four wheel drive!
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#896288 - 05/30/14 01:17 PM
Re: Pulling flywheel on 1997 Merc 40hp
[Re: WABOWMAN]
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Dick Nipples
Registered: 03/08/99
Posts: 28170
Loc: Seattle, Washington USA
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Richard and I ran into a similar problem last fall, and we found a pinhole leak in the fuel line...at high RPMs as it was really sucking gas it would suck in enough air to kill the performance.
Changed out a $30 fuel line, problem solved.
Fish on...
Todd
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#896289 - 05/30/14 01:34 PM
Re: Pulling flywheel on 1997 Merc 40hp
[Re: WABOWMAN]
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Poon it! Poon it! Poon it!
Registered: 08/08/06
Posts: 1721
Loc: Yarrow Point
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Then with a simple light cruciut tester probe the coil wires. Find which one isn't working. You mean a timing light? I did pull all the coils last night and inspection and testing (resistance) on the primary & secondary and they all are in-spec. Again the challenge is the failure is intermittent/when warm, and that's hard to get to in a driveway setting... I believe running at 3000+ RPMS on flush muffs is likely to do more harm than good, so I'm going to have to start visiting the lake a bunch... When it's failed, it's not failed in the way I typically think of for fuel-starved. The RPMs just drop down in a step and stay there. It's not like it's going up/down/up/down as fuel supply surges... That's why I'm focused on ignition.
Edited by IrishRogue (05/30/14 01:36 PM)
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The charm of fishing is that it is the pursuit of what is elusive but attainable, a perpetual series of occasions for hope. -John Buchan
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