Eliminating the gremlins of this newly acquired 1972 Evinrude V4 100HP electric shift. Starts fine,, smooth idle, runs fine up to around 1500 RPM, if I bring the throttle up, at about the same point each time it will bog down, always at the same point. It doesn't sputter or fight and it never stalls, it's as if it's running on two cylinders (maybe 3) all of a sudden, instead of the smooth roar of WOT, it's almost a machine gun muffled engine sound, wa wa wa wa wa, you can hear the ignition of individual cylinders it seems, and the overall volume of the engine noise is softer than it would normally be. It never makes it up to WOT, I don't have a tach, but if I had to guess somewhere around past 1500-2000 RPM it will get in this mode. if I back down the throttle, it will surge briefly with a normal fast RPM sound and then settle down to a regular slow /fast idle speed as I continue to back the throttle down. I could let it go forever like this, but because it doesn't sound very good, I back off after a few seconds. It does it everytime, I try to bring the throttle past a certain point. Also when it does this, there is a noticeable reduction in power, it doesn't just level off, it's like going over a cliff. I checked the timing and made sure it was 28 degrees advanced, and with my timing gun verified all 4 plugs were getting pulsed at all points on the throttle from idle to wot. I've squeezed the primer bulb when this problem is occuring, and it doesn't help- it actually stays pretty firm so I don't think it's a fuel pump problem. I did link and sync.
Does this sound like a high speed jet carb problem on one or two cylinders? The next time I go out - I'm going to take the boat out with a friend and spray fuel through the throats one at a time (or two at a time) to see if it run better. I'll report back on that test later.
Are there any tips/techniques for spraying fuel through the throats? A regular pump spray bottle? Set it to make a mist, or just a **** stream and shoot it in there? Should I do one throat at a time, or should I do two?
The plugs looked fine, I suppose I could replace them too, but haven't. I figured if they fire at low RPM why would they stop at high RPM. I thought it might be a timing problem, but I checked it and I've got it dead on 28 degrees advanced at WOT and around 5 at idle.
I checked compression at the beginning of the season, and all 4 cylinders were around 115 to 120 each. I've retested compression and it's still the same. The only other info I can provide- a couple times I took it immediately out of the dock, and I was able to get up on plane with normal WOT for about a minute max, and then the motor will slowly but surely start to get softer and softer, gradually getting to that muffled sound and finally reach that wa wa wa sound. And then from there, anytime I push the throttle too far forward, at the same point it it does the wa wa wa wa
Does this sound like one or two cylinders have plugged high speed jets- can a motor run fine up to 1500 or 2000 RPM or so just using the low speed inlets?
Does this sound like a high speed jet carb problem on one or two cylinders? The next time I go out - I'm going to take the boat out with a friend and spray fuel through the throats one at a time (or two at a time) to see if it run better. I'll report back on that test later.
Are there any tips/techniques for spraying fuel through the throats? A regular pump spray bottle? Set it to make a mist, or just a **** stream and shoot it in there? Should I do one throat at a time, or should I do two?
The plugs looked fine, I suppose I could replace them too, but haven't. I figured if they fire at low RPM why would they stop at high RPM. I thought it might be a timing problem, but I checked it and I've got it dead on 28 degrees advanced at WOT and around 5 at idle.
I checked compression at the beginning of the season, and all 4 cylinders were around 115 to 120 each. I've retested compression and it's still the same. The only other info I can provide- a couple times I took it immediately out of the dock, and I was able to get up on plane with normal WOT for about a minute max, and then the motor will slowly but surely start to get softer and softer, gradually getting to that muffled sound and finally reach that wa wa wa sound. And then from there, anytime I push the throttle too far forward, at the same point it it does the wa wa wa wa
Does this sound like one or two cylinders have plugged high speed jets- can a motor run fine up to 1500 or 2000 RPM or so just using the low speed inlets?