Troy_from _Oz
Petty Officer 2nd Class
- Joined
- Sep 29, 2002
- Messages
- 126
Hi there guys, hope you all had a great Xmas.<br /><br />Sorry in advance for the long post, but I think i have to explain the background to this problem first.... 
<br /><br />I have a 71 4cyl merc650 which has good compression (~130 on each pot). A while back, my distributor packed it in so I had to hunt around for a new 2nd hand one. The new one that I got had a slightly different pickup assembly than the old one, but i dont think thats causing a problem. Anyways, on replacing the dist (after doing link/sync), I had the feeling that I wasnt getting full power/revs out of the motor when i took it out on the water. <br /><br />Incidentally, I had also been struggling to find the cause of a rattle that had been bothering me. As it turns out, the last owner had the starter motor replaced - at which time the flywheel wasnt torqued up properly... hmmm. Evidently, the key sheared last time I was out and have had to have new keway machined into flywheel etc.. on replacing fwheel, there was a little bit of slop @ TDC, so there is a _small_ possibility the dist belt might be one tooth out (although the engine fires up perfectly and runs smoothly - so maybe it isnt a problem).<br /><br />Anyways, back out on the water and still no full power as i didnt have full power before doing fwheel - im thinking its not due to dist belt settup. I also noticed that the last owner or mechanic had set max advance screw fully out - indicating lagre max adv setting. But with this setting the motor ran fine. Its just when i do it by the book (with timing light) and set max adv to 38 - (actually i think it may be at about 36-37 at the moment) there is a big loss of power/speed.<br /><br />Finally to my question... Is there any way of setting it by ear? as you can do with a car dist on older engines that are slightly worn and where optimum setting may not be at the book value?? if so how do you do it? is it meant to be done at WOT? <br /><br />Will my advance being set 1-2 deg out make that much of a diff? <br /><br />thanks in advance<br /><br />Troy
<br /><br />I have a 71 4cyl merc650 which has good compression (~130 on each pot). A while back, my distributor packed it in so I had to hunt around for a new 2nd hand one. The new one that I got had a slightly different pickup assembly than the old one, but i dont think thats causing a problem. Anyways, on replacing the dist (after doing link/sync), I had the feeling that I wasnt getting full power/revs out of the motor when i took it out on the water. <br /><br />Incidentally, I had also been struggling to find the cause of a rattle that had been bothering me. As it turns out, the last owner had the starter motor replaced - at which time the flywheel wasnt torqued up properly... hmmm. Evidently, the key sheared last time I was out and have had to have new keway machined into flywheel etc.. on replacing fwheel, there was a little bit of slop @ TDC, so there is a _small_ possibility the dist belt might be one tooth out (although the engine fires up perfectly and runs smoothly - so maybe it isnt a problem).<br /><br />Anyways, back out on the water and still no full power as i didnt have full power before doing fwheel - im thinking its not due to dist belt settup. I also noticed that the last owner or mechanic had set max advance screw fully out - indicating lagre max adv setting. But with this setting the motor ran fine. Its just when i do it by the book (with timing light) and set max adv to 38 - (actually i think it may be at about 36-37 at the moment) there is a big loss of power/speed.<br /><br />Finally to my question... Is there any way of setting it by ear? as you can do with a car dist on older engines that are slightly worn and where optimum setting may not be at the book value?? if so how do you do it? is it meant to be done at WOT? <br /><br />Will my advance being set 1-2 deg out make that much of a diff? <br /><br />thanks in advance<br /><br />Troy