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18hp mercury problem

M

Merc18

New member
Hey all, I'm new here...

To get started I just bought a little John boat that I completely redid. It came with a 1982 18hp 2 stroke mercury.
I was searching the only serial number I could find and it says that it's a 25hp.
So I searched about that and found that my motor can be turned into a 25hp by changing the carb and the exhaust. It said the carb number was bc1c for the 25hp and that's what's on this motor.

To the point... I changed all of the gaskets on the carb and replaced what seemed to be fuel lines because they looked horrible. I can get the motor to run for a minute or two at full throttle but the motor doesn't run like it's at full throttle. After that minute or two it dies and won't start again unless I remove the spark plugs and dry them off.
Then it does the same thing again.

What's the issue here?
 
Sounds like the carb is flooding. How does it idle?

Jeff

PS: I believe the porting is milder in the block. IF you buy a new, replacement block for them, however, they supply only the 20/ 25 hp block so you end up with "more power!" (to quote Jeremy Clarkson)
 
The porting is the same on all three hp's. They don't offer the chrome bore blocks anymore so you get the newer Mercosil block as a replacement, which has better casting in the exhaust area...
 
When I start it for the first time of the day, it will idle for maybe 30 seconds then die. Then I can't get it to idle anymore.
2 days ago when I got it started and hit the throttle the motor would Rev up, but it would take a while to get to high rpm.
Why would the carb be flooding?

Also where can I get one of these blocks for my type of motor?

I'm new to all of this stuff this is my first time doing anything like this.
 
No I havent. I'm scared to lol.
I'm really hoping each one is the same or at least close.

I'm thinking it may have something to do with the timing and my throttle adjustment was off. It wasn't even touching the spring thing whatever it's called.
 
It was the needle. Letting to much gas in and flooding.
So I took it for a test run and the starter died on me.
So I tried to pull start it then the rope broke.
Luckily I had my trolling motor Cause it was almost dark.
 
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