470 low speed question

[Lamont270]

I checked the choke that day and the flap was wide open and I looked for excess gas and it seemed ok. Also the flame arrestor is clean. Is there a low speed jet that could be out of whack? It is the Mercruiser carb. What brand of plug is recommended, I have Autolite plugs in it now and was thinking about switching to NGK. I will look into the Petronix kit I was going to put one in this winter when I had the engine out but ran out of spare cash after the other repairs.

[spareparts]

NGKUR5 , it has one single adjustment screw under the float bowl

[Lamont270]

Thanks all, I'll grab some NGK's and I will be out on the St.Lawerance river later this week and will mess with the carb a little. If that does not work I'll grab a carb kit and rebuild it..

[breastman569]

how is you fuel pump? i was having the same problem but at idle under load it would die, we did change out the points and that didnt seem to help we thought that due to the points that after running at high speeds it would be stuck to advance, that seem to help a little but still die at low speeds. so next we changed out the plug wires, cap rotor and fuel pump and it runs so smooth, the best its run in 30 years. i know your thinking if it had a bad fuel pump would it effect it at high speeds? all i know is when i took the old pump apart all the diaphragms reall hard as a rock.

[cfelton]

Follow Spares advise and get a Pertronics electronic ignition to replace the points/ condenser. I also installed the matching Flamethrower coil from Pertronics and it made a HUGE difference in starting, idling, pickup and WOT! Its probably the best upgrade I've done to my 170. Also, it never hurts to get a rebuild kit and go through your carburator. They're really easy to rebuild. One thing I had trouble with was a small spring in the bowl needle, had to go back in and replace it with a solid pin in the needle to get it to stop loading up when at idle. Hope that helps!