Re: J/E Lightwin 3/4 HP
The last year of the 3hp (1968) was essentially the 4hp (1969 onwards) rated at a lower RPM.<br /><br />The 1967 and prior 3hp were quite different in the powerhead area. Much different intake (fewer reeds), and they lacked any needle bearings at all (which is why they should remain on a 32:1 or 40:1 diet, NOT a 50:1 diet). Even the 4s only had a needle bearing at the upper crank main and I prefer to run them on an enrichened oil/gas mix of no less than 40:1. I'm not sure where in the lineage that they added the needle bearing to the upper main - may have been before 1967. Someone with parts books should be able to look that one up. I believe they made them "full jeweled" by the late 1970s with steel bearings on all the moving parts in the powerhead. <br /><br />The old style 3s also used wider piston rings, which meant a bit more friction, which also was helped by the extra oil.<br /><br />I've run many of both and for the most part you wouldn't notice much seat-of-the-pants difference between the 3 and the 4 unless you were about 12 years old running a very light jonboat that would actually plane off with that little power.<br /><br />- Scott
<br /><br />EDIT: I did some checking and it seems that the 4 got it's full bearings in '78, which is before it became the 4.5hp.