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OK, let’s hear from a few of you!!
Cheers, Adrian
can you provide any design advise on mufflers? i notice that paw mufflers on the larger engines reduce power quit a bit. looking to build my own. capacity? design? noise? one on each side to increase capacity?
PAW mufflers are a bit rudimentary Rob – they merely restrict the exhaust opening area but don’t provide a great deal of internal volume. Some volume in a muffler is necessary to act to some extent as a “damper” to reduce the inevitable back pressure and allow continued discharge of exhaust gas even after the exhaust ports have closed. The PAW mufflers also favour the exhaust ports facing the muffler rather than serving all ports equally. Mufflers generally don’t work too well with radially-ported diesels.
Cheers,
Adrian
Hi Adrian.I have bought,sold and repaired many Merco motors and test run them all.However,I have a ‘61 which insists on running backwards,something which has never before happened.I have stripped it and found nothing untoward.I thought maybe the cylinder was the wrong way round but it was not and I don’t think that this would cause it anyway.I don’t have an electric starter but anyway,it should start OK by hand as all the others did,but no such luck.Having front rotary induction,it should’nt run backwards anyway,should it?
I wasn’t aware of such an engine, Roy, but the only way that I can conceive of this behaviour occurring is if the crankshaft induction port is specifically timed to promote reverse running. That could only be done by the factory. As you say, any FRV engine inherently has “one way” timing which shouldn’t allow it to operate correctly in reverse (although some FRV engines will start in reverse but won’t run very well in that direction). It’s possible that MERCO made a few engines which were timed for reverse rotation – if they did so, that’s very interesting information!
Suggestion – fit a 2-blade prop which is positioned so that it points straight up at top dead centre. Turn the engine to bottom dead centre (180 degrees) then pot oil in the intake. Rotate the prop very slowly in either direction and note the prop angle off the vertical at which the oil begins to drop as the crankshaft port opens. Do this in both directions from bottom dead centre. Then you’ll have the timing of the crankshaft induction port in your engine and can determine the running direction for which it’s timed.
Good luck! Let me know what you find out!
Cheers,
Adrian