Re: 1979 johnson 115 loss of power
Dropping a cylinder is not always so bad to call for a rebuild. It can be caused by a lot of things, not all of which so bad. If you've ruled out fuel related problems, I have found generally you're looking at:<br /><br />-1 Powerpack/ Coil<br /><br />-2 Loss of Compression<br /> a) Blown Head gasket<br /> b) Stuck Ring(s)<br /> c) Worn cylinder(s)<br /> d) Detonated piston<br /><br />I have had all these conditions in my 77 115, probably in reverse order
At least once it was my own fault.<br /><br />-1 pull all plugs, turn motor over and check for spark (easier with 2 people)<br />-2 a) check for steam cleaned plug(s)<br /> b,c) compression check<br /> d) Look for molten metal shorting out plug electrode (yes it happened to me)<br /><br />2 b) actually caused my motor to stall out above a certain in-gear RRM. All other scenarios identical to yours, it just seems to hit a wall and will not jump up on plane. Generally this is either fuel, or an unbalanced motor where it can't spin up since one cyl is being carried by the others. For some reason at lower RPMs it is not as noticeable. I know I have rebuilt many carbs, drained fuel and ended up in one of the above scenarios after ruling fuel issues out.<br /><br />Generally when I had 2)c and before 2)d occured, I could start and idle fine, run WOT all day, and then only when hot it would always stall at idle. Generally it would run better in condition 2)c and even 2)d than 2)a or 2)b, but in reality it was in need of much more work.<br /><br />Also I had replaced some fuel line once and it had a kink at a tight turn between the vacuum driven fuel pump and the carbs. In this case it would come up on plane and at WOT give me about 2 minutes before falling off plane due to fuel bowl starvation. If I kept it at only ~75% WOT it would stay up on plane indefinitely. Solution: buy the expensive pre-molded fuel line pieces for those tight turns between fuel pump and carbs.<br /><br />Based on your reports, to take a guess it would seem to me either fuel related or possibly a head gasket blown.<br /><br />George
