Sidhewynder
Cadet
- Joined
- Dec 15, 2010
- Messages
- 17
Hi Everyone. A friend has a 1981 Johnson 140 loosing power.
History -> J140TLCIM. He just bought the boat Had trouble with the tilt/trim which we fixed (thanks all). He said when he ran the boat it never got up on plane. I know Speedometers in boats are kinda useless, but for comaprison it never got past 22mph on the speedo. It idled fine, and didn't really stutter, but no power. The boat had sat for several years.
Last night we tore the carbs down and cleaned them, resetting the floats just a bit. Put the boat in the water and she took right off. Came up on plane nicely and after a little trimming the speedo read about 31mph. We tooled around for about 5mins like kids in a candy store when suddenly I thought he cut power. He didn't move the throttle. Now we're off plane, again about 22mph. I did the usual, checked for leaks - none. Cracked open the fuel tank to see about venting - no change. Pumped the bulb a little - no change. I even had him blip the choke - no change. We headed back to shore and suddenly the motor picked back up. Up to plane again. I manually operated the throttle and the boat sped up a little more. The odd thing was this...
While I was looking at the motor (carbs right in front of me) I noticed to the left mid-side of the enging some bubbling. Upon closer inspection it appeared to be fuel (bluish tint). I tried looking at schematics so I could give a bitter description of what it was, but couldn't find it, so here goes general terms.
There seems to be a small box or casing upon with an electrical strip and several wires are attached. That "box" appears to be removable with a few small bolts. The edge of the box seems to butt up against the back edge of the intake manifold. Its hard to tell because the cylinder heads were sorta' over top it. I would say the box and electronics are in the back 1/3 of the motor. (Wow.. how confusing is that)
Anyway there were a series of small bubbles there. The bubbles seemed to die down as the throttle was reduced.
Questions: 1) I would think that a leak would cause problems all the time. We had no problems for 5mins, then loss of power. Could that leak be doing that?
2) Is that box removable? Could there possibly be a leak in the intake gasket and just getting pushed out there? I didn't seem far enough back to be an exhaust cover leak, but its hard to tell. It also didn't appear to be a leak where the cylinder case opens.
3) From what I've read I'm wondering if this isn't an electrical problem. I read where you could check to see if plugs are firing using a timing light. I'm not really a mechanic, so could someone please explain how that's done.
Thanks...
History -> J140TLCIM. He just bought the boat Had trouble with the tilt/trim which we fixed (thanks all). He said when he ran the boat it never got up on plane. I know Speedometers in boats are kinda useless, but for comaprison it never got past 22mph on the speedo. It idled fine, and didn't really stutter, but no power. The boat had sat for several years.
Last night we tore the carbs down and cleaned them, resetting the floats just a bit. Put the boat in the water and she took right off. Came up on plane nicely and after a little trimming the speedo read about 31mph. We tooled around for about 5mins like kids in a candy store when suddenly I thought he cut power. He didn't move the throttle. Now we're off plane, again about 22mph. I did the usual, checked for leaks - none. Cracked open the fuel tank to see about venting - no change. Pumped the bulb a little - no change. I even had him blip the choke - no change. We headed back to shore and suddenly the motor picked back up. Up to plane again. I manually operated the throttle and the boat sped up a little more. The odd thing was this...
While I was looking at the motor (carbs right in front of me) I noticed to the left mid-side of the enging some bubbling. Upon closer inspection it appeared to be fuel (bluish tint). I tried looking at schematics so I could give a bitter description of what it was, but couldn't find it, so here goes general terms.
There seems to be a small box or casing upon with an electrical strip and several wires are attached. That "box" appears to be removable with a few small bolts. The edge of the box seems to butt up against the back edge of the intake manifold. Its hard to tell because the cylinder heads were sorta' over top it. I would say the box and electronics are in the back 1/3 of the motor. (Wow.. how confusing is that)
Anyway there were a series of small bubbles there. The bubbles seemed to die down as the throttle was reduced.
Questions: 1) I would think that a leak would cause problems all the time. We had no problems for 5mins, then loss of power. Could that leak be doing that?
2) Is that box removable? Could there possibly be a leak in the intake gasket and just getting pushed out there? I didn't seem far enough back to be an exhaust cover leak, but its hard to tell. It also didn't appear to be a leak where the cylinder case opens.
3) From what I've read I'm wondering if this isn't an electrical problem. I read where you could check to see if plugs are firing using a timing light. I'm not really a mechanic, so could someone please explain how that's done.
Thanks...