Re: 115 omc filler blocks
I'll tell you how we found this. Years ago a good buddy was rebuilding a 140 on a commercial boat. As expected the filler blocks were all half melted and twisted and broken. Obviously the motor was being lugged severly, not unusual on this type boat.
Obviously my buddy wanted to replace the blocks but the commercial guy didn't have the $$ for new ones and the necessary machine work. We both agreed that they should be replaced but the owner insisted they not be.
OK, fine. My buddy said he'd rebuild the motor but he wanted to break it in and run it to make sure it would be OK. He asked if we could run this guys powerhead on my ski boat motor, another 140 - just a couple years older. No problem, but we both expected it to be down slightly on prm, not down on power necessairly but rpm.
Well, it turned about 150 rpm more than my ski powerhead. Hummm.....
We were running a 140 type crossflow on the Allison race boat at the time. Stock powerhead rules. We were at about 7200 with it. Took the blocks out and poof - 7400. If you get looking, once the blocks are out of the way the exhaust has a lot more space to get out and into the adaptor plate. The bottom 2 cylinders could shoot exhaust straight out and down without going thru the manifold. The top two coud exit either thru the manifold or down & out.
OK, we'll take this one step further. We cut the filler blocks in half and put the top ones in each side and left the bottom ones out. That way each exhaust was kept completely seperate until it exited the powerhead.
That didn't change a thing. Same as running no blocks.
Over the years we've left them out of several V4's. Not many people see the difference in 100 or so rpm. The bottom line is - it doesn't hurt a thing.
Later we tried that with a 235 V6. At 5800 we lost about 50-75 rpm by taking the blocks out.
