78 mercury thunderbolt 20 hp

Someone help.....I have a 78 merc 20 hp and it runs excellent but its very hard to start. It takes me anywhere from 10-15 pulls to get it going!! But the funny part is that once I have it running once it will start first pull for the rest of the day!! Any ideas??

Re: 78 mercury thunderbolt 20 hp

If your choke butterfly is not the 1 piece like shown in it following link, #17 replace it or solder it so it is 1 piece, or the carb is missing #18 either could be your trouble. If they are both in place, then the idle mixture is lean or the float is set to low.

Re: 78 mercury thunderbolt 20 hp

Thanks for the reply Laddies, Im new to this but your reply said the following link.....am I missing the link??lol

Re: 78 mercury thunderbolt 20 hp

Wow , it's not on mine either,I screwed up lets try again
http://www.mercruiserparts.com/Show...81&bnbr=5&bdesc=CARBURETOR+ASSEMBLY,+COMPLETE

Sorry

Re: 78 mercury thunderbolt 20 hp

Ok...now that I looked at the diagram,, It is a bit different then mine, maybe its not a 78 afterall, I guess I screwed up! my serial number is 7062033...is it a 76? I was just going on what I was told when I bought it. any ideas on this one...?

Re: 78 mercury thunderbolt 20 hp

It's got to be 70 as they didn't make any that started 76 it's a 1975 Canadian built 20 but my manual says its that carb maybe a the Canadian engines use a differant carb or it's been changed, can you find a number or something on the carb?

Re: 78 mercury thunderbolt 20 hp

Every 20hp of this model has usually been problem to cold start for me until I tried the following:
1. pump the primer bulb tight
2. put throttle on fast idle
3. pull choke out (make sure it is closing fully)
4. slow roll the motor over (I am assuming you have a pull rope) about 10 to 12 compression strokes. It might crank with the slow roll, if so, very quickly push the choke in before it dies. If you didn't push the choke in fast enough and the motor started but died during the slow roll, push the choke in and pull start quickly.
5. Assuming no start with the slow roll, after 10 to 12 compression strokes, with the choke still out, pull the rope quick. When the motor starts, push the choke in super fast before it dies.

This method has consistently worked for me with a properly tuned motor. Good luck.