Carb rebuild, I discovered much larger than spec high speed orifice plug

[renegade15]

1990 Johnson 70 hp, vro disconnected, using premix-50:1

Symptoms are that it starts and idles fine, upon throttling up the engine starts to do what feels like a violent miss. I explained this to dealer they said sounds lean, rebuild carbs. If I throttle back and turn the engine off then back on it runs fine and will do so as long as it is still warm.

I started the cleaning/rebuilding process and damaged the bottom carb orifice plug as it is in very tight. I am soaking in pb blaster to try to loosen it. I figure I'll have to get a new one of those so when I look online I discover that the one spec'd is 52d, the middle and top carb both have 63d. I've verified this with the dealer. I'm thinking there might be something else going on here.

I bought this boat about 1.5 years ago and it ran fine till this past december. I use it about once a month for a day of fishing on the flats around Tampa Bay.

I will check compression tonight and report back, but figured I'd get a few other things to look at from you-all as well.

Thanks!

 

[HybridMX6]

Re: Carb rebuild, I discovered much larger than spec high speed orifice plug

Someone possibly went with larger carbs trying to get more power?

 

[wesley pipes]

Re: Carb rebuild, I discovered much larger than spec high speed orifice plug

well if it ran fine when you got it and it had the jets in it but now your having problems i dont think the jets would be the problem. if they wernt then why would they be now you know? not 100% on that but i would say you had a pluged up highspeed jet if it was missing like you say at high speeds. there in the bottom of the bowl were everything settles and normally the first thing plugged up.

 

[5150abf]

Re: Carb rebuild, I discovered much larger than spec high speed orifice plug

If it ran fine I wouldn't change them, I have a 50 and mine aren't what the manual says they should be but the motor runs great, if they are all 3 the same and it runs good i would leave them alone.

As Weslet said it sounds like dirty main jets, the ones in the float bowl, I have had my motr run the same way and I pulled those jets, looked factory fresh so i put them nback in but still had my problem til i took the out and actually cleaned them, then it ran like a top.

Use a stranded copper wire and pull back strands till it just fits then slide the jet back and forth a couple times, works like a charm.

 

[renegade15]

Re: Carb rebuild, I discovered much larger than spec high speed orifice plug

I guess I'll order a new 63d to put in to replace the one I mangled and see how it runs.