Just an FYI...
Over the winter I performed a cheap rebuild of my OMC 3.0 since I had to take it out due to the rear freeze plug leaking. Long story short, I pulled dished pistons out of the motor and I accidentally ordered flat top pistons when I ordered the rebuild kit from ebay; my machinist told me it would probably be ok, so I used them anyway. I still had my worries...
I took it out for the first time last weekend using mid-grade pump gas with the initial timing advanced at 4 deg. After a good warm up, it started pinging at about 3/4 throttle. I kept retarding the timing until the pinging was completely gone and ended up retarded at 1 deg. I haven't tried to adjust the mechanical advance yet. I'm going to run premium gas next trip...
Even with the retarded initial timing, the change in performance was very noticeable as I gained 4-5mph (on gps) and it planes out a lot easier. With a little more tuning, I expect I'll get a little more performance. If you're looking for a way to gain some easy hp, these pistons thus far seem to be a good option. Only time will tell in regards to the durability of the motor with the increased compression.
Over the winter I performed a cheap rebuild of my OMC 3.0 since I had to take it out due to the rear freeze plug leaking. Long story short, I pulled dished pistons out of the motor and I accidentally ordered flat top pistons when I ordered the rebuild kit from ebay; my machinist told me it would probably be ok, so I used them anyway. I still had my worries...
I took it out for the first time last weekend using mid-grade pump gas with the initial timing advanced at 4 deg. After a good warm up, it started pinging at about 3/4 throttle. I kept retarding the timing until the pinging was completely gone and ended up retarded at 1 deg. I haven't tried to adjust the mechanical advance yet. I'm going to run premium gas next trip...
Even with the retarded initial timing, the change in performance was very noticeable as I gained 4-5mph (on gps) and it planes out a lot easier. With a little more tuning, I expect I'll get a little more performance. If you're looking for a way to gain some easy hp, these pistons thus far seem to be a good option. Only time will tell in regards to the durability of the motor with the increased compression.
