Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: 1990 100 mercury 4 stroke was stalling alot today. Any advise
Posted by Finallygotawhaler on 06/29/20 - 6:06 PM
#1
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
Posted by Finnegan on 06/29/20 - 9:39 PM
#2
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.
Posted by biggiefl on 06/30/20 - 6:07 AM
#3
Wow...Must have bought an experimental engine. The only 4 strokes made in 1990 were Honda and under 10hp.
What Finnegan said.
Posted by renoduckman on 06/30/20 - 7:28 AM
#4
Fuel pump/fuel filter.
Posted by Finallygotawhaler on 06/30/20 - 7:55 AM
#5
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...
Posted by Finallygotawhaler on 06/30/20 - 7:59 AM
#6
Typing error.
IT IS A 2 STROKE....
MY FAULT....
Posted by Finallygotawhaler on 06/30/20 - 9:52 AM
#7
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.
Posted by Finallygotawhaler on 06/30/20 - 12:38 PM
#8
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....