View Full Version : splutters and misfire after 4 sets? 84 S&S

09-13-2007, 04:44 PM
My MC runs great for the first 4 sets or so and after that it splutters and misfires when accelerating. Give it 30 mins break and its fine again then starts doing the same. Only had the boat a few weeks as I need a slalom boat and my 22ft V drive doesn't cut it!

The engine is old and seen some action but for the first 4 sets it runs great, accellerates like nothing I've skied behind before and tops out around 44mph. There is quite a bit of blow by vapour coming out the pcv hose when warm so i guess its a little tired but I'm sure it has some years left!

Replaced points, condenser and cap. Sorted the wiring as previous owner had done away with ballast resistor and it was burning out the points/over heating the coil. The carb is only 2 years old and is ery clean.

Could it be the coil is breaking down when it heats up after being run at around 14V with no resistor? It seems like its losing too much power to be say just one plug breaking down and unlikely more than one?

Engine seems to hold 160-180 temp steadily although the engine compartment does seem quite hot. There is no vent in the engine cover like my old 86 had so I may well add a vent in there.

Any ideas?

09-13-2007, 05:18 PM
Go ahead a install a electronic ignition conversion kit, that replaces the points/condenser, add the new 12v coil and follow the instructions by bypassing the ballast resistor. Vent the engine compartment to remove the heat and run the bilge blower all the time too to get the heat out.

09-14-2007, 05:33 AM
I was going to get the electronic ignition kit but as I'm in the UK shipping and taxes makes it pretty damn expensive. I was lucky to get a new tune up kit for only £25 and in the past I've found well set points to be pretty reliable.

I'll cut a hole in the engine cover today and had been running the blower all the time. The misfires seemed to clear a little bit when the hood was lifted when running so I'm also going to check the air hoses from the front vent.

Having an efi'd and perfect pass'd v drive spoils you and I forgot how these older boats need a bit of tinkering!

09-15-2007, 09:55 AM
Changed the plugs and coil and its running like a champ again. Rode about a dozen sets on the butter this morning and all good....

Well until the fuel pump went! Its not pumping any fuel. Checked the lines and such and removed the pump to lift it manually and still no go so just ordered a new pump. Will be out of action for a few days but at least it ran well.