I'm no marine mechanic, or any kind of mechanic for that matter....but I am somewhat mechanically inclined. If anyone can lead me in the right direction, it'd be much appreciated.
Recently acquired 1987 Merc 15hp 2 stroke, single carb, dual cylinder.
First time out on the water started first pull and ran for 10 minutes, then sputtered out and wouldn't restart all night....had to come in on trolling motor. Next day, same thing... started right up then wouldn't stay running. Third day same thing.
So I decided to do some investigating before just handing it over to a mechanic:
First I replaced all the fuel. Bulb has good pressure and carb is defintely getting gas.
I took the carb apart and cleaned it. However it was already spotless. Bowl is moving freely and all jets/ports clean.
Then I checked spark with spark testor and both cylinders aggressively jumping 7/16" with blue spark.
Here's where it gets weird:
During my testing, I happened to turn the motor over with the top plug removed. It started right up and ran like a top. So I switched the bottom plug and wire to the top cylinder....won't run. Then I switched plugs/wires back to original position, put top plug in loosely and won't run.
While the engine runs with top plug removed, gas spurts out of the top plug hole, so I know it's getting gas. Then I got worried maybe I didn't have compression. Tested compression and have 90 psi, which seems ok.
I didn't take the flywheel apart to check for a sheared key but the marks on the flywheel seem to line up with TDC on top cylinder.
So now I'm wondering:
-If it was a bad switch box would I still be getting great spark on both cylinders? And why won't the top cylinder fire at all when I put bottom plug/wire into it?
-Reed valve?
-Possibly getting water in top cylinder fouling the plug when it's in the hole?
-If the cylinder was flooding with too much mixture, wouldn't both cylinders be since it's a single carb?
Recently acquired 1987 Merc 15hp 2 stroke, single carb, dual cylinder.
First time out on the water started first pull and ran for 10 minutes, then sputtered out and wouldn't restart all night....had to come in on trolling motor. Next day, same thing... started right up then wouldn't stay running. Third day same thing.
So I decided to do some investigating before just handing it over to a mechanic:
First I replaced all the fuel. Bulb has good pressure and carb is defintely getting gas.
I took the carb apart and cleaned it. However it was already spotless. Bowl is moving freely and all jets/ports clean.
Then I checked spark with spark testor and both cylinders aggressively jumping 7/16" with blue spark.
Here's where it gets weird:
During my testing, I happened to turn the motor over with the top plug removed. It started right up and ran like a top. So I switched the bottom plug and wire to the top cylinder....won't run. Then I switched plugs/wires back to original position, put top plug in loosely and won't run.
While the engine runs with top plug removed, gas spurts out of the top plug hole, so I know it's getting gas. Then I got worried maybe I didn't have compression. Tested compression and have 90 psi, which seems ok.
I didn't take the flywheel apart to check for a sheared key but the marks on the flywheel seem to line up with TDC on top cylinder.
So now I'm wondering:
-If it was a bad switch box would I still be getting great spark on both cylinders? And why won't the top cylinder fire at all when I put bottom plug/wire into it?
-Reed valve?
-Possibly getting water in top cylinder fouling the plug when it's in the hole?
-If the cylinder was flooding with too much mixture, wouldn't both cylinders be since it's a single carb?
