A number of years ago, there was an article in one of the popular
boating magazines about this. The article recommended Shalers Rislone
and gave a lengthy story about why its a good smoking lube. At the
time, I had a boat with a pair of 188 HP Graymarine engines and every
spring I had a few sticky valves when I fired up for the first time. I
began smoking with Rislone and no more sticky valves. The article went
on to say that Risone will stick to the cylinder walls and coat the
valves. Regular 30 weight oil will drain down over the winter. I
still use it on my smaller engine, a 5.0 OMC Cobra. Hope this helps
someone.
Happy boating, Norm