Re: johnson 40hp
You're going to need to determine where your problem is first - ignition or fuel.<br />The common problem for ignition problems on this engine are ignition coils cracked due to age. They arc over at weird times causing all sorts of power pick up/loss. So a pull-start speed spark check isn't absolute. One is warrented though.<br />The ignition system is very nearly completly independant, so it's very common to loose spark in one cylinder, but not the other. If you seem to be going at half speed at WOT, then this is likely your problem. Pull each spark lead and test your running to prove it. If pulling the top lead makes the engine die, you know it's firing. If there's no change, it's not.<br /><br />Fuel problems are usually clogged carburator jet problems. You can find out if your running lean by putting some pre-mix in a spray bottle and spraying some down the carb's throat while running. If it's running lean, it will pick up when you do this.<br /><br />I highly recomend you get your hands on a repair manual. You can order them from this site, or often borrow one from your library.<br /><br />Good luck!<br /><br />EDIT: Oh, please post your engine's model number with your question. I take it you ment the 1968 40hp engine you mentioned earlier.
