Atomic 4 compression

[Unregistered]

With the sailing season over for me this year I've been thinking about Atomic 4 winter projects. I tested the compression on my engine and got readings of 88, 90, 90, and 98 psi for cylinders 1, 2, 3, and 4. Do these readings fall within the acceptable range? In your newsletters you mention 100-110 psi as being good and 80 and below as low. Two years ago I pulled the cylinder head and ground/lapped the valves as descibed in your overhaul manual. The engine runs quite well and moves my Pearson 30 at up to 6 knots with a two-bladed folding prop. I probably put 75-100 hours on the engine this season between motoring out to the race course for Wednesday evening races and several cruises and overnight races. The oil pressure is 38 psi and the water temperature (I have FWC) is about 180 at cruising speeds. I have had some problems with the transmission, namely, slipping in forward and losing reverse completely twice. Forward was fixed by tightening the forward adjustment one notch ( had to do this about a year ago also) The second time I lost reverse I tightened up the adjusting nut quite a lot and reverse is working again but I suspect I'm running out of adjustment room because of excess play in the linkage parts. Can these parts be replaced without removing the engine from the boat? Access to the engine is fair.

I would greatly appreciate any thoughts you have on these issues and on the likely general health of the engine.

[Don Moyer]

It's very unlikely that you will run out of adjustment capability in your reversing gear. We have never had to replace forward clutch disks or a reversing brake band in all the years we've been in the business of rebuilding Atomic 4's, and I think it's even less likely that the linkage is somehow wearing out. I would disconnect the shifting cable from the lever on the engine and then work the shifting lever itself to see if you still feel the same excessive play in the system.

Your compression readings are fine, particularly in view of your excellent performance. Since you worked on the valves two years ago, it might be good to check the valve clearances one more time, but if access is too poor to get to the valves, I wouldn't even worry about this issue too much.

Don