Hi Monti.<br /> Your Johnson 90hp is a 1981.<br /> Spark plugs Champion L77J4 gap@ .040 or 1.0mm torque 17 1/2 to 20 1/2 ft lbs or 24- 27 Nm.<br />Ignition timing 28 degrees @ 4300-4600 rpm.<br />hope this helps, good luck.
Hi Alcan,<br /><br />Thanks again for that info. You mentioned that the ignition timing must be 28 degrees <br />@ 4300-4600 rpm, can you tell me what the ignition timing must be set at when the engine is idling?
With regards to the same motor mentioned above, my dad wants to add a little more power to it. He needs to know what the cylinder head dimensions are (including/excluding the waterjacket) because he wants to skim the head. How much can he skim off the head and what other changes can he make?
The best bet to add power to your boat is to add bigger engine. The money you will spend to tweak the engine that you have now probably will cost you just as much as a bigger engine would cost you. Do what I did.. I traded my 86 mecury 60hp to a 93 johson 90hp... It cost me 700.00 plus my motor..
