Re: My Boat
That's the other benefit of replacing the midleg and lower unit with a one piece: You have a larger selection of props. Those old thrust pin 18 splie props, while nice looking simply are not available new. you need to find them on ebay. AND---No hubs are available for repair of a spun prop.
Now, as far as porting: Do both bypass and exhaust on the three cylinder engines. Do not raise the top of the ports as this changes timing. That's OK for racing but not for recreationasl boating. I used to square the ports by hand with a dremel and carbide bit but that puts too much vibration into my fingers. Now, I chuck an end mill into the drill press and simply remove the inter-port webs, leaving the center web and two oval ports. A lot quicker and I have one test engine which will be run later in the season to see if it works as well or better.As you can see from the photos, I have also experimented with porting the cylinder liner and piston skirt on the bypass side.
To tell if your lower unit is a 2 to 1, put the unit in forward gear and back up the prop untill it engages the drive dogs, Now mark the prop and turn the drive shaft 2 full turns. If the prop spins only once, it is 2 to 1 . If it spins about 1 1/4 turns, then the lower unit is 1.73 to 1. In the two piece lower units, I THINK that the only 2 to 1 was the three cylinder 90 but there is a possibility that one of the 4 cylinder engines (like 135) also had it. As far as I know, the old 85 had the 1.73.ratio.
If you elect to port the piston skirts, You must first clean the block and have the piston, rod, and crank assembly connected. Then turn each piston to top dead center and drill through the block and piston at the same time. I used a 0ne inch hole drilled with a one inch countersink resting againts the two corners of the bypass. After porting remove everything and clean well--you can see the amount of metal chips in the photos.
