Re: Indexing plugs on carbed engines
It does not hurt, and it improves plug life, it also gives more consistant readings too: this is because the plug always reads darker under the negative electrode, and also it reads darker on the side oriented towards the intake and booster ports. Thus a plug indexed towards the intake will read darker than one oriented towards the exhaust, giving the impression of a difference in mixture when in relaity, there is none. On multi-cyliner outboards, it makes good sense to do this as the plug readings will be more uniform, given the engine is in proper tune.
I have found it also reduces the tendancy of the engine to foul out when starting if you over choke, and when you have been idling or trolling for long periods, it helps reduce plug fouling and sputtering when you accelerate and the engine is loaded up with excess fuel and oil in the cases.
It does not cost anything to do it, and almost everyone who races two cycles (karts, motocross, watercraft) does it as well. By the same token, not doing it does not harm the engine.
Need more convincing? Model airplane glow plugs for R/Cmodel planes, cars and boats use have an "idle bar" to stop droplets of mixture from quenching the plug element. The idle bar is similar to the negative electrode on our outboard plugs in that it sheilds the center electrode. This is needed for engines with a throttle that experience extended periods of low speed running, such as when taxing, and on descent to final approach for landing. Thus the electrode on our spark plugs can be indexed to do the same thing.
