15 HP Carburetor/Reed block gasket?

[bigboat606]

I have a 1997 Mariner 15 hp that has been having starting problems when cold only. The first pull, the engines fire right up a few times - almost runs- and stops. This engine used to always start on the first pull! After that it is very difficult to start. The only way I start it is to pull the cowling and advance the throttle (a lot). When started, it runs and idles great. I have followed the manual's suggested starting procedures including priming it three or four times. I decided to pull the carburetor at which point I checked the primer pump. It shoots fuel 4 feet! - so the engine is definitely getting fuel when starting. Note I rebuilt the carburetor last year due to rough running and since have had the starting problem - but the engine runs and idles great otherwise.

I ran into a blog where another person was having the same problem as I am and it was suggested it could be an air leak between the carburetor and reed block. When I removed the carburetor I noticed a formed rubber o-ring type seal embedded into the reed block and no other gasket. The guy in the blog had the same-no gasket. But when I checked the Mercury parts catalog diagrams a gasket is shown. Also my carb rebuild kit had a gasket and no replacement molded o-ring type seal. Does anyone know if I should use a gasket between the carburetor and reed block even though there was not one on the engine originally? I bought the engine new and am the only one to have worked on it, so I'm fairly certain it did not come with one - especially since the other guy's engine had the same. And if I don't need a gasket, any ideas as to my starting problem?

 

[Texasmark]

Assuming that the Oring is in a groove and mates with a flat surface on the other side of the interface it's a very effective/reliable reusable seal.....if still springy and not permanently mashed flat. However, if in doubt, or if it will make you feel better, make one from some gasket material you can get from an auto parts store; get fuel tolerant material, and get some blue RTV. Usually you put that gasket on dry, but if you are worried about it, put a film of RTV on both sides of the gasket and don't worry about it and leave the Oring in for good measure.