Hello, I'm new and hoping to get some help.
My friend and I have been working on a Johnson 175 Ocean Runner that has sat for a long time, so I'll tell our history with it to date in hopes that it helps. I think we may have been dealing with numerous issues, possibly including ignition, cooling, and fuel.
On our first outing, we ran fine for around a half hour before we started getting a continuous alarm while running and at idle. From what I've read, that was probably it overheating. The engine was surging rapidly though as though someone was slamming the throttle back and forth between about 1/2 throttle and wide open. It was pretty violent and maybe 1 second intervals. I've heard of the overheat protection mechanism, but given the violence of the surging, I'd be surprised if that was what was happening. Once it died, we could not get it to start again for a long time, until it finally did run, sound the alarm and die again before we could get back to the ramp. To me it seemed like it could be both a overheating situation as well as a fuel problem.
After this first outing, we flushed the fuel system, rebuilt the carbs (upon doing so it appeared someone else had done so recently, but they did appear to be leaking around the float bowl gaskets prior to our rebuild), and changed out the thermostats. One of the thermostats was all plugged up, so that likely explains the overheating. We did not mess with the idle mixture on the carbs which on this model is the only fuel mixture adjustment I see without swapping orifices.
On our second outing, the fuel leakage was eliminated, It also appeared to resolve our overheating problem. However, we ran it shortly at wide open throttle and the alarm sounded and shortly after, the motor died and would not restart. However unlike the previous outing, the alarm stopped when not running. About an hour later we got it to start again, and it ran pretty well at idle and it ran pretty well at 1/2-3/4 throttle, however if we took it to WOT, the alarm would sound but it would go away again as soon as you back off. We tested that several times over, and it was just like flipping a switch. I've read this is indicative of running lean. We did not mess with any of the orifices, so they should be the right size unless the previous owner did something to them.
Anyone have any ideas what it could be? From reading online, I've also seen where it could possibly be the stator or the powerpack. Given how it seems to be linked to WOT, I am tempted to play with the high-speed orifices, but unless the original owner did something to them, I can't think of why they would be the wrong ones. Does anyone know what the factory orifices should measure?
Thank you in advance for any help.
My friend and I have been working on a Johnson 175 Ocean Runner that has sat for a long time, so I'll tell our history with it to date in hopes that it helps. I think we may have been dealing with numerous issues, possibly including ignition, cooling, and fuel.
On our first outing, we ran fine for around a half hour before we started getting a continuous alarm while running and at idle. From what I've read, that was probably it overheating. The engine was surging rapidly though as though someone was slamming the throttle back and forth between about 1/2 throttle and wide open. It was pretty violent and maybe 1 second intervals. I've heard of the overheat protection mechanism, but given the violence of the surging, I'd be surprised if that was what was happening. Once it died, we could not get it to start again for a long time, until it finally did run, sound the alarm and die again before we could get back to the ramp. To me it seemed like it could be both a overheating situation as well as a fuel problem.
After this first outing, we flushed the fuel system, rebuilt the carbs (upon doing so it appeared someone else had done so recently, but they did appear to be leaking around the float bowl gaskets prior to our rebuild), and changed out the thermostats. One of the thermostats was all plugged up, so that likely explains the overheating. We did not mess with the idle mixture on the carbs which on this model is the only fuel mixture adjustment I see without swapping orifices.
On our second outing, the fuel leakage was eliminated, It also appeared to resolve our overheating problem. However, we ran it shortly at wide open throttle and the alarm sounded and shortly after, the motor died and would not restart. However unlike the previous outing, the alarm stopped when not running. About an hour later we got it to start again, and it ran pretty well at idle and it ran pretty well at 1/2-3/4 throttle, however if we took it to WOT, the alarm would sound but it would go away again as soon as you back off. We tested that several times over, and it was just like flipping a switch. I've read this is indicative of running lean. We did not mess with any of the orifices, so they should be the right size unless the previous owner did something to them.
Anyone have any ideas what it could be? From reading online, I've also seen where it could possibly be the stator or the powerpack. Given how it seems to be linked to WOT, I am tempted to play with the high-speed orifices, but unless the original owner did something to them, I can't think of why they would be the wrong ones. Does anyone know what the factory orifices should measure?
Thank you in advance for any help.