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1990 100 mercury 4 stroke was stalling alot today. Any advise
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| Finallygotawhaler |
Posted on 06/29/20 - 6:06 PM
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Posts: 13
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Joined: 04/30/20
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So ive always had a little trouble when starting the boat and it always stalled alot at low rpms. At medium speed and fast speed the boat ran great.
Today on the bay I was riding around and i suddenly lost throttle slowly. It felt like i was losing power slowly.
After priming the bulb, the boat would run for about a couple hundred yards then bog out again.
I changed the plugs and the same results.
I then had my wife keep squeezing the primer bulb and i made it home 6 miles.ran great as long as the bulb was primed...
All good gas...
New plugs...
New fuel lines....
What do you think is the problem?
Any ideas
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| Finnegan |
Posted on 06/29/20 - 9:39 PM
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Posts: 1926
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Joined: 05/02/08
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I don't think Mercury has ever made a 100HP four-stroke outboard. My guess is you have a 4 cylinder 2-stroke engine, one of those "2 + 2" models that people either love or hate. Below 1800 RPM it runs on 2 cylinders (two cylinders/carbs do not have a low speed idle circuit) and then all four come on at 1800RPM.
I have two guesses as to your problem.
1. Fuel tank venting is clogged, not letting fuel flow properly
2. Engine fuel pump has failed.
I would take it in for professional service.
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| biggiefl |
Posted on 06/30/20 - 6:07 AM
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Posts: 890
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Joined: 05/08/06
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Wow...Must have bought an experimental engine. The only 4 strokes made in 1990 were Honda and under 10hp.
What Finnegan said.
24 Whalers so far.... |
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| renoduckman |
Posted on 06/30/20 - 7:28 AM
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Posts: 81
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Joined: 08/12/05
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Fuel pump/fuel filter.
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| Finallygotawhaler |
Posted on 06/30/20 - 7:55 AM
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Posts: 13
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Joined: 04/30/20
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Finnegan wrote:
I don't think Mercury has ever made a 100HP four-stroke outboard. My guess is you have a 4 cylinder 2-stroke engine, one of those "2 + 2" models that people either love or hate. Below 1800 RPM it runs on 2 cylinders (two cylinders/carbs do not have a low speed idle circuit) and then all four come on at 1800RPM.
I have two guesses as to your problem.
1. Fuel tank venting is clogged, not letting fuel flow properly
2. Engine fuel pump has failed.
I would take it in for professional service.
My apologies, its 2 stroke, i dont know why i put 4...
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| Finallygotawhaler |
Posted on 06/30/20 - 7:59 AM
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Posts: 13
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Joined: 04/30/20
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Typing error.
IT IS A 2 STROKE....
MY FAULT....
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| Finallygotawhaler |
Posted on 06/30/20 - 9:52 AM
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Posts: 13
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Ok .
Thank you guys
It was the fuel pump.
There was a rip in one of the diaphragm and one of the springs was broken.
Bought a new kit from a local marine parts supplier.
Part # 18-7817. Sierra
Replaces mercury mariner 21-42990A7
The kit was slightly different than what was in my pump. I had to punch 2 small holes in one of the diaphragm to make them the same as my old factory diaphragm.
Ill pit it back on and let you know how it runs.
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| Finallygotawhaler |
Posted on 06/30/20 - 12:38 PM
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Posts: 13
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Joined: 04/30/20
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All right...
Starts right up...
Idles awesome....
Doesnt stall...
Will take it out under load tomorrow and see how it does.
Its the best ive seen it run since i bought it....
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