1979 Evinrude 15 (15904e) carburetor

I posted last week about the hard starting of this engine. Runds great once started. It was suggested the choke plate may not be closing tightly or the carb ports under the top welch plug may be blocked. I removed the plug, ran a wire thru each port, no blockage, then shot carb cleaner thru. Choke plate closes firmly. Of course it started after injecting the carb cleaner. But not this morning. I stuffed a shop towel in its throat and she fired right up, so clearly this is the right path.

Question: this carb has a butterfly that has holes in it. There is an "air silencer" which attaches to the carb with a seal, which I have removed so I can watch the carb, stuff a rag in its throat etc.. Is it possible the choke draw is inadequate because the "silencer" is not attached to the face of the carb? Could that be why there are holes in the butterfly plate? Seems unlikely since the silencer is a two piece plastic unit with no seal between the upper and lower halves so it isn't air tight. I am running out of ideas to solve this lack of choke issue. When I replaced the welch plug I sealed it with nail polish too.

Re: 1979 Evinrude 15 (15904e) carburetor

here is a link to the carb diagram showing the "silencer"

http://www.boats.net/parts/search/BR...LD/parts.html#

Re: 1979 Evinrude 15 (15904e) carburetor

If the silencer is on or off it should not make any difference when it comes to cold starting your motor. Have you checked your compression? It would be interesting to know the numbers as poor compression can make it difficult to start. Best of luck. Rick.

Re: 1979 Evinrude 15 (15904e) carburetor

How is the carb to intake gasket? Did you replace it? Rick is correct, I have started many of these 9.9/15's without the airbox on. Like he said, the next look is compression, low compression will cause this issue.

Re: 1979 Evinrude 15 (15904e) carburetor

100% agreement with Rick...as additional Info here's the cold start procedure for a 1978 9.9 that I get to wrench on...

1.pump fuel line bulb until firm
2. Pull choke on, advance throttle as far as it will go in neutral
3.Pull starter rope..first pull < never tries to fire >, second pull < couple of
chugs>, push choke in 1/2 way, third pull it starts...most times, sometimes
the fourth pull is necessary

the rest of the story is: when I put the carb back on after rebuilding it, I set the the carb roller slightly beyond its center when aligned with the embossed mark on the timing cam.ie: the timing is slightly advanced as the throttle plate < the butterfly with the 2 holes> is just beginning to open..additionally, this motor had 80# top, 78# bottom cylinder last time I checked it <last year>
The powerpack and both coils are new <cdi products>

Re: 1979 Evinrude 15 (15904e) carburetor

I mentioned in the original post the compression is good. I just recovered the engine from a mechanic who replaced a power pack. First thing he did was check compression. I did replace the carb to intake gasket when I rebuilt the carb a month ago. This is definitely a choke issue. Where does that upper chamber under the welch plug draw its fuel from? The high speed jet when the choke plate is closed?

I can see (feel) I'm going to be pulling this carb again. Getting tire of it. All that does is wear out gaskets if I can't get to the bottom of this

Re: 1979 Evinrude 15 (15904e) carburetor

yes...all the fuel enters through the high speed jet

Re: 1979 Evinrude 15 (15904e) carburetor

Maybe a reed (leaf) valve isn't seating correctly??

Re: 1979 Evinrude 15 (15904e) carburetor

Should still start and run with 1 bad reed, i'm thinking carb. Those holes under the plug are air bleed holes, no fuel exits them, it's all via the high speed jet.

Re: 1979 Evinrude 15 (15904e) carburetor

billybuck1 said:

I mentioned in the original post the compression is good. I just recovered the engine from a mechanic who replaced a power pack. First thing he did was check compression. I did replace the carb to intake gasket when I rebuilt the carb a month ago. This is definitely a choke issue. Where does that upper chamber under the welch plug draw its fuel from? The high speed jet when the choke plate is closed?

I can see (feel) I'm going to be pulling this carb again. Getting tire of it. All that does is wear out gaskets if I can't get to the bottom of this

Click to expand...

Sorry about that. It seems I must have forgotten what your original post said. So, your compression is good. I'm at a loss if your carb. is clean, compression is good and you have spark. If I think of something I'll be sure to let you know. Rick.

Re: 1979 Evinrude 15 (15904e) carburetor

BK...unless I'm misinterpreting this cutaway drawing in the manual OMC Evinrude 9.9/15 hp..it shows a fuel/air misture being drawn up into an area slightly behind the needle end of the low speed mixture needle when the throttle butterfly is closed either at idle or in the start position..in other words...there's no where else for the fuel/air mixture to enter the carb throat with the throttle plate closed....if I'm wrong, I'd like to be corrected,as this is how I've been thinking it had to travel...up into the idle mixture needle area and out those 3 holes in the "well"