Mariner Magnum 40 1992 lost full power

[bentuxworth]

Hi

I have just bought a Zodiac MkII with a Mariner Magnum 40hp (4 cyl) from 1991/2. Just trailed it a long way, then launched today. Started OK, a bit smokey but that soon cleared up. I got it up to full throttle, got to a good speed and was planing nicely, for a couple of mins, then power suddenly dropped away. Now it runs at about half power, not enough to plane. It will rev very fast in neutral, but not when in gear. It sounds smooth (ie I don't think it is failing to fire on all cylinders). I wondered if the throttle linkage had slipped, but it seems to operate normally, and as I say will rev very high in neutral.

Only other thing I did was change from a 13 pitch to a 15 pitch prop. I wondered if maybe I have over-propped it, but given that it ran fine for a couple of minutes (and the boat was not heavily laden - just me and three kids) it seems unlikely.

Any thoughts? I'm on holiday in Portugal, and this is really going to spoil things if I can't sort it out. Theories gratefully received.

 

[starcraft1982]

Re: Mariner Magnum 40 1992 lost full power

check compression on all cylinders FIRST.couldve run lean for many different reasons and killed a cyl. or 2.then my next theory would be high speed windings in stator.