H€PHÆ$TU$
Active Member
1998 Sportster 1800, dual 717 engines. First some history, will try to make as short as possible.
-Bought boat knowing it would need some work, but it had new engines and upholstery, so was a good deal.
-PO had oil injection issues on previous motors, deleted the entire oil system. Boat runs premix now.
-All new poly fuel lines.
-One of the first things I noticed was that the fuel return line for the right engine was pinched closed using a zip tie.
-There were several metal wire brushes laying around the boat.
-Unpinched return line, took boat out. Left engine ran relatively fine. (Will expound on this later.) Right engine surged above 4000 rpm, would go to 6000, return to 4000 repeatedly. Classic sign of fuel starvation, so I ran it at 4000rpm to get home.
-Replaced inline filters, cut old ones open, they were new. Obviously PO knew he was having fuel issues.
-Surmised that pinched return line was feeble attempt to band-aid fuel starvation issue.
-Rebuilt right side carb using SBT kit. Internal fuel filter was completely clogged with crap. Replaced it as part of rebuild.
-Took boat out for test run, both engines ran relative good. (Will expound later.)
-Took boat on 45-minute drive across bay. This is where I will expound on my "relatively good" running conditions. Neither engine will idle below 2500rpm in the water, even if I back the idle screws out completely off the lever. Above 5000 rpm boat periodically takes off on its own, both engines randomly rev to 7-8k rpm on their own. I have to pull throttles back to get them back under control.
-Shut boat down while we swam and played for about an hour at the beach. With boat off, I used the batteries to inflate a tow-able tube.
-Started engines back up to tow the tube but right engine suddenly sounds weird. No longer has the metallic clinking idle, but a smoother, muffled, rumbling noise instead. Engine will not rev above 3000 rpm and sounds bad as it does. Shut right engine down, pinched water line, limped home on just left engine.
-Pulled spark plugs on both engines. Both engines plugs are black and slightly wet, indicating rich conditions. (Plugs were new before this.)
-Performed compression test on both engines. 140-150 psi in all cylinders.
-Right engine still running weird, won't rev.
So now that the history lesson is over, there are some clues here that I am interpreting. PO obviously knew he had fuel issues with that right engine. PO did not know about, or did not want to change, internal carb filter. PO performed one or more band-aid repairs to try to get fuel to that engine. (Pinched return line.) The presence of multiple wire brushes indicates that he was making tuning runs and pulling the plugs to read and clean them between runs. Ultimately he replaced the plugs, gave up, and sold it. Knowing that he knew he was starving for fuel, I assume the adjustment screws are both all the way out / all the way rich. (I haven't had time to check yet. Wed. will be my next work day.) I assume that those screws being all the way rich combined with me replacing the internal filter has resulted in the carb overloading the engine with fuel resulting in my poor running condition. I'll find out for sure on Wed. But the thing that I can't wrap my mind around is that it ran relatively fine for 45 mins before these symptoms suddenly exhibited themselves between startups. I assume the high idle condition and the engines running away are both also results of rich conditions. Especially the way that they ran away at the exact same rpm every time. That rpm probably corresponds to the % throttle where the high speed adjustment takes over. (Or something like that.)
Any further insight before I launch the boat again on Wed. to attempt to start tuning the carbs would be greatly appreciated. Hoping to get the attention of @Bills86e in particular. Thank you in advance.
-Bought boat knowing it would need some work, but it had new engines and upholstery, so was a good deal.
-PO had oil injection issues on previous motors, deleted the entire oil system. Boat runs premix now.
-All new poly fuel lines.
-One of the first things I noticed was that the fuel return line for the right engine was pinched closed using a zip tie.
-There were several metal wire brushes laying around the boat.
-Unpinched return line, took boat out. Left engine ran relatively fine. (Will expound on this later.) Right engine surged above 4000 rpm, would go to 6000, return to 4000 repeatedly. Classic sign of fuel starvation, so I ran it at 4000rpm to get home.
-Replaced inline filters, cut old ones open, they were new. Obviously PO knew he was having fuel issues.
-Surmised that pinched return line was feeble attempt to band-aid fuel starvation issue.
-Rebuilt right side carb using SBT kit. Internal fuel filter was completely clogged with crap. Replaced it as part of rebuild.
-Took boat out for test run, both engines ran relative good. (Will expound later.)
-Took boat on 45-minute drive across bay. This is where I will expound on my "relatively good" running conditions. Neither engine will idle below 2500rpm in the water, even if I back the idle screws out completely off the lever. Above 5000 rpm boat periodically takes off on its own, both engines randomly rev to 7-8k rpm on their own. I have to pull throttles back to get them back under control.
-Shut boat down while we swam and played for about an hour at the beach. With boat off, I used the batteries to inflate a tow-able tube.
-Started engines back up to tow the tube but right engine suddenly sounds weird. No longer has the metallic clinking idle, but a smoother, muffled, rumbling noise instead. Engine will not rev above 3000 rpm and sounds bad as it does. Shut right engine down, pinched water line, limped home on just left engine.
-Pulled spark plugs on both engines. Both engines plugs are black and slightly wet, indicating rich conditions. (Plugs were new before this.)
-Performed compression test on both engines. 140-150 psi in all cylinders.
-Right engine still running weird, won't rev.
So now that the history lesson is over, there are some clues here that I am interpreting. PO obviously knew he had fuel issues with that right engine. PO did not know about, or did not want to change, internal carb filter. PO performed one or more band-aid repairs to try to get fuel to that engine. (Pinched return line.) The presence of multiple wire brushes indicates that he was making tuning runs and pulling the plugs to read and clean them between runs. Ultimately he replaced the plugs, gave up, and sold it. Knowing that he knew he was starving for fuel, I assume the adjustment screws are both all the way out / all the way rich. (I haven't had time to check yet. Wed. will be my next work day.) I assume that those screws being all the way rich combined with me replacing the internal filter has resulted in the carb overloading the engine with fuel resulting in my poor running condition. I'll find out for sure on Wed. But the thing that I can't wrap my mind around is that it ran relatively fine for 45 mins before these symptoms suddenly exhibited themselves between startups. I assume the high idle condition and the engines running away are both also results of rich conditions. Especially the way that they ran away at the exact same rpm every time. That rpm probably corresponds to the % throttle where the high speed adjustment takes over. (Or something like that.)
Any further insight before I launch the boat again on Wed. to attempt to start tuning the carbs would be greatly appreciated. Hoping to get the attention of @Bills86e in particular. Thank you in advance.
