I have a customer that brought me his boat with twin Yamaha Engines and wanted it gone through from A-Z . Says he just bought the boat and it has been sitting for 2 years.
I checked compression fuel and spark, all good.
Scanned both engines for codes, no active faults.
Stbd engine number 6 injector was completely dead and only had 35 psi at VST
Port engine had 52 psi
Removed all 12 injectors, sent off to Brucato to have them checked and serviced.
Number 6 injector was bad, and 4 others were out of spec. Could only find 3 new OEM injectors , so purchased 3 new OEM injectors and 2 reman injectors from South Bay Fuel Injectors.
So I ended up installing 3 Brand new injectors, 7 reman from Brucato and 2 reman from South Bay.
Also replaced the 4 mystery filters in the High Pressure pump.
Removed both VSTs, disassembled, cleaned and replaced filters.
Stbd vst pump was missing O-ring for pump, and that is where the low pressure was coming from.
After reassembly, both engines now have constant 52 PSI at the pressure port.
Port engine, started and ran, but started hard and ran erratic, surging at idle. Tried to give it throttle in and out of gear, was sluggish and finally got up to rpms, but after bringing throttle back, stays running at very high idle for about 30-45 seconds, finally drops back down to slow and erratic idle. High pressure pump pressure was all over the place at rpms, from 50 psi to 750 or 800. Pressure finally stabilized at idle.
I unhooked the TPS and engine starts and runs like a dream, but of course doesn't throttle up very good. Reset tps at .50 and rechecked, same thing.
Checked voltage range on tps from idle to full throttle with key off, and it is responding, but not going as high a it should at idle according to the Yamaha service manual.
Starboard engine cranked over really well, but started extremely hard, finally started, but also ran very erratic at idle, surging constantly. Monitored high pressure, was running consistently at 750-800 psi, never moved off of it. Disconnected tps, and engine runs like a dream, starts and idles just fine, even throttles up extremely well, which is rather unexpected to me beings that the tps was unhooked. With tps connected and reset it is just a dog to throttle up, and tps voltage is going up and down as it should, except it too is not reaching the top end voltage according to the manual.
I am at my wits end with these, and I want to point out that I am not an expert on these motors, as I haven't worked on very many of them. Any help would be greatly appreciated!
P.S. I did check the throttle linkage to make sure that it is mechanically coming back to idle as it should, and it is working perfectly. Also I want to note that the motors were both being run on a hose with no load.
I checked compression fuel and spark, all good.
Scanned both engines for codes, no active faults.
Stbd engine number 6 injector was completely dead and only had 35 psi at VST
Port engine had 52 psi
Removed all 12 injectors, sent off to Brucato to have them checked and serviced.
Number 6 injector was bad, and 4 others were out of spec. Could only find 3 new OEM injectors , so purchased 3 new OEM injectors and 2 reman injectors from South Bay Fuel Injectors.
So I ended up installing 3 Brand new injectors, 7 reman from Brucato and 2 reman from South Bay.
Also replaced the 4 mystery filters in the High Pressure pump.
Removed both VSTs, disassembled, cleaned and replaced filters.
Stbd vst pump was missing O-ring for pump, and that is where the low pressure was coming from.
After reassembly, both engines now have constant 52 PSI at the pressure port.
Port engine, started and ran, but started hard and ran erratic, surging at idle. Tried to give it throttle in and out of gear, was sluggish and finally got up to rpms, but after bringing throttle back, stays running at very high idle for about 30-45 seconds, finally drops back down to slow and erratic idle. High pressure pump pressure was all over the place at rpms, from 50 psi to 750 or 800. Pressure finally stabilized at idle.
I unhooked the TPS and engine starts and runs like a dream, but of course doesn't throttle up very good. Reset tps at .50 and rechecked, same thing.
Checked voltage range on tps from idle to full throttle with key off, and it is responding, but not going as high a it should at idle according to the Yamaha service manual.
Starboard engine cranked over really well, but started extremely hard, finally started, but also ran very erratic at idle, surging constantly. Monitored high pressure, was running consistently at 750-800 psi, never moved off of it. Disconnected tps, and engine runs like a dream, starts and idles just fine, even throttles up extremely well, which is rather unexpected to me beings that the tps was unhooked. With tps connected and reset it is just a dog to throttle up, and tps voltage is going up and down as it should, except it too is not reaching the top end voltage according to the manual.
I am at my wits end with these, and I want to point out that I am not an expert on these motors, as I haven't worked on very many of them. Any help would be greatly appreciated!
P.S. I did check the throttle linkage to make sure that it is mechanically coming back to idle as it should, and it is working perfectly. Also I want to note that the motors were both being run on a hose with no load.