Loss of power

[Djerlandson]

This summer, as we were making way north in Lake Michigan, we set out for a 60 mile motor sail from Charlevoix to St. Ignace. Imediately we noticed we did not have full cruising power. Only about 1/2 rpms and thrust. Something is wrong, we turned back to Charlevoix to explore. I’ll skip the forward gear slipping out which we seemed to solved. After that, the rpms and power issue remained. We decided to pull into the engine doctors at Irish Marine to evaluate. After testing the ignition system/timing, good, then carberation and fuel, good, a driving test still evidenced low rpms and power. Next they checked compression. Lower range of acceptable but consistent through the cylinders. Next they did a “leak down” test. Cylinder 1, acceptable, at 10%. Cylinder 2 at 26%. Not so good. Cylinder 3 over 50% and cylinder 4 over 60%. Air is leaking out around the intake valves. As the mechanic put it, although everyone is getting up, only 1 1/2 of our cylinders are going to work!

After crying for a night, we decided we would wait for favorable winds and limp home to Muskegon. Without stressing the engine, she runs fine. I clean the spark plugs after every 10 hours of engine running, can’t hurt.

Now, August 1st, we are home in Muskegon. Ugh, way to early!

I’m thinking an engine tear down for new Valves and new rings while we’re at it.

Any thoughts?

[Dave Neptune]

D, first welcome to the MMI Afourian Forum!

Before tearing down run a bit of MMO or TCW-3 (2 stroke) oil in the gas at 100:1. The valves may just be a bit sticky. For a sudden loss of power as in last time it ran fine I doubt it is excessive wear. Run the engine for a while even in the slip against the dock lines and note any difference in performance by the valves seating better.

For a valve to burn in an A-4 it would take a while as there just isn't that much heat to again do it suddenly.

Did the "mechanic" check the valve adjustment?

Did the power "rise and fall" while underway?

Dave Neptune

[tenders]

You're sure the propeller is clear of entanglements? These symptoms happen in seasonal salt water starting in late August...and it's often barnacles. (I realize you're in sweet water.)

[Djerlandson]

Thanks for the input. I checked and ruled out prop obstruction first off.

Sticky Valves: seems like sticky valves could cause the “leak down” test results. It seemed like the most recent 20 to 30 hours of motor sailing the engine seemed just fine. Full cruising rpms and normal speed. Maybe the valves are seating properly now? Is it still advisable to add a 100:1 mix of 2 cycle oil to lubricate the valves? What are risks of this?
I’m going to do some engine power testing this weekend motoring into expected 15 to 20 mph winds.

[Dave Neptune]

D, re the 100:1 mix. It is for lubricating the valves. Many on this forum run the MMO @ 100:1 full time. It is not enough to do any sort of fouling and it does a good job of carrying the oil to the valve stems (the part that sticks) and the cylinder walls. The TCW-3 is specifically designed to burn with gasoline while lubricating. That's just over an ounce per gallon.

Are you using any additives at all?

Dave Neptune