First post here, but I've been lurking in the background for a few weeks. I have a 1985 Wellcraft American 170 (16.5' open bow runabout) that I purchased back in July. I've only had the boat out a couple of times, but both times I felt as though the little 4 banger didn't sound quite right. Although I could get up on plane, it took a while to get it up and the engine sounded like it was laboring. It starts and runs great, so I chalked it up to being a bit underpowered. After that first time out, I started looking at some of the forums to see if I could find others that had experienced the same symptoms with this boat and engine combo. Because I can only reach around 3500 rpm at WOT, I started wondering if my prop might be too big (stainless 15 x 19p) and considered purchasing something smaller. The second time out, I confirmed that the engine was topping out around 3500 rpm but I paid a bit more attention to some of the symptoms. Again it sounded like it was laboring a bit. However, it starts and idles perfect. It has a bit of a hesitation through part of the throttle range, but I chalk that up to a tired accelerator pump in the carburetor. Gas is good, the engine is tight - good compression, timing was right on - 8 degrees BTDC. After considering this for a while, I started to suspect that the timing was not advancing at higher RPM. That's where the engine sounded labored. At WOT, the engine sounded like it WANTED to run, but just couldn't quite manage. So this morning, I pulled the boat out of the barn, grabbed the timing light and checked the advance at 2500 RPM. Nothing. The base timing did not change.
Cut to the chase - the rotor shaft was frozen to the distributor shaft, which made the centrifugal advance not work at all. I took the distributor apart - a pretty simple job requiring nothing more than a screwdriver - freed up the shafts, oiled the appropriate parts and put it back together. Voila! I reset dwell and base timing and tested. The timing is now advancing as it is supposed to. I have not had it in the water yet - I'll have to wait for a couple of weeks, but I expect that the difference will be night and day. I should be able to pull that prop with this boat at around 4200-4400 RPM. I'll check back in with empirical data as soon as we hit the water.
Moral of the story, if your boat just doesn't seem to have the high end that it once had, if it is struggling, don't forget to check the simple things like your centrifugal advance.
Oh and by the way, this engine was tuned by a "professional" when it was summerized this year. I guess professionals are just not what they used to be.
Ron
Cut to the chase - the rotor shaft was frozen to the distributor shaft, which made the centrifugal advance not work at all. I took the distributor apart - a pretty simple job requiring nothing more than a screwdriver - freed up the shafts, oiled the appropriate parts and put it back together. Voila! I reset dwell and base timing and tested. The timing is now advancing as it is supposed to. I have not had it in the water yet - I'll have to wait for a couple of weeks, but I expect that the difference will be night and day. I should be able to pull that prop with this boat at around 4200-4400 RPM. I'll check back in with empirical data as soon as we hit the water.
Moral of the story, if your boat just doesn't seem to have the high end that it once had, if it is struggling, don't forget to check the simple things like your centrifugal advance.
Oh and by the way, this engine was tuned by a "professional" when it was summerized this year. I guess professionals are just not what they used to be.
Ron