1969 mercruiser 160 WOT, RPM, speed, and prop

[paul]

Hey guys,

     Can anyone tell me what my RPMs should be at WOT, and also what prop size I should be running?  I can't seem to get above 2900 RPM-could be a number of things-faulty tach, linkage not reaching full throttle, but I have no idea what prop I should be using, and what RPM I should be hitting.  I don't know of anyone else with a single inline 6, so I also have no idea what speed it should be capable of-I know, I know, SLOW!

Paul

[David]

Mercruiser manual will tell you rpm range.  Pull your air breather cover with motor off and open throttle.  Look down the carburator throat to see if butterfly is fully open.  You'll have to make sure your engine is healthy and functioning properly and make sure your tach is accurate before you can prop it correctly.  So, I would check throttle opening, tach accuracy, compression check engine, replace plugs & wires, adjust timing and service ignition system.

[paul]

Thanks Dave.  Gonna start checking some of those, and report back.  Here's the prop that's on there now- 48 78116 a4 15P.  I also have a Quicksilver SS prop that came with the boat(but not on) 48 93272 a5 15p.  These both seem to be quite a bit off from where the Mercruiser and formula people thought I ought to start at 19 or 21p.  I don't know what to think, so I'll start with the tune-up, butterfly check and check the tach.

BTW, I think that "48" is a mercruiser indicator, is "78116" a model or series?  and where is the diameter specified?  I believe that it's a 14.5" diameter, but shouldn't that be in the number also?

Paul

[David]

Sorry Paul, can't help you with those Mercruiser numbers.  Maybe someone else here can.