Yamaha F225 running rich, consuming more fuel than it should

[choogenboom]

I have a pair of 2004 F225s. Last trip out I could not get one of them to increase RPM beyond 4900 when the other engine would go to 5300. The last 25% of throttle motion produced no change in RPM BUT it did produce a change in fuel consumption. With both engines at full throttle one was running 5300 RPM and 14 GPH and the other ran 4900 RPM and 16 GPH. My best guess is its running rich due to a problem with the TPS. Some other useful background information: (1) boat was struck by lightning, both ECU's are new. (2) TPS were not replaced after lightning strike (3) I have the YDS cable+software so can do advanced diagnostics if needed. (4) at less than 4500 RPM fuel use on both is the same. (5) I have verified the fuel management meters are accurate in that fuel burned according to guage == what I add to fill the tanks.

Am I on the right track or should I be looking elsewhere? Whats normal GPH for WOT?

Thanks in Advance,
Chris

[boats.net]

Connect it to YDS and see if codes, then run and monitor YDS to see any thing is out of range, test fuel pressure.

[choogenboom]

Connect it to YDS and see if codes, then run and monitor YDS to see any thing is out of range, test fuel pressure.

will do, thanks.

[choogenboom]

Connect it to YDS and see if codes, then run and monitor YDS to see any thing is out of range, test fuel pressure.

Fuel pressure - Both engines the same. 42 PSI when key turned to run, 41-42 PSI with engine at idle (700 RPM) and 48 PSI at WOT. Note I never saw 38 PSI at idle as stated in the manual and I did not see a spec in the manual for what I should expect at WOT.

No codes. I did see two unusual things.

1) on both engines, after long idle and with cover off, only heated up to 144F. After running at WOT with cover off warmed up to 200F, then after 16 minutes at idle came back down to 144F. I am used to car engines that heat up to about 160-170F and then the thermostat holds it there very steady. Note that both engines were just serviced by a Yamaha Master Tech to the tune of $4K which included new thermostats and pressure control (aka popit) valves. Also, BOTH engines ran as hot as 212 F as read from the data log in the last trip which seems way to hot to me. Stuck thermostats?

2) The manual states the thermoswitchs are supposed to conduct starting at 183-194F. I assume that means I should have gotten an overheat horn and the engine should have gone into limp home mode if the temperature, as reported by the YDS, exceeds 194F. It DID exceed that on BOTH engines but I did NOT get an overheat horn. Are my assumptions correct?

3) Specs state timing if from 0-24 BTDC. I saw on BOTH engines 29-30 BTDC at 3000, 3500, 4000 and 4500 RPM. Where they diverged is at greater 4500 RPM. the "good" engine came down to 24 BTDC at 5000 RPM and the "bad" engine was at 15 BTDC at 5000 RPM. At 5300RPM, good engine was 26 BTDC and bad at 18 BTDC. at WOT good engine was 5555 RPM and 19 BTDC and bad engine was 5300 and 18 BTDC. Shop manual says "check timing" but does not tell how, if the timing is off, to adjust it.

Your help is much appreciated.

Chris

[choogenboom]

problem solved

Spoke to Yamaha Tech support and they put me on the scent. The main clue is it was the stbd engine that was not making enough RPMs at WOT. They said its normal for the port engine to run about 300 RPM lower than the stbd engine at WOT due to the counter rotating prop. They advised me to check compression and fuel injectors. I ran a test where I would remove a plug wire one cylinder at a time and then run to maximum RPM and note the result. I discovered that disabling cylinder 5 made almost no difference to the WOT RPM and cylinder 2 made little difference whereas the rest of the cylinders made a big difference, so I knew I had a problem with cylinders 5 and 2. Cylinders 2 and 5 happen to share a common ignition coil so I swapped coils between the engines and there was no change so that ruled out ignition. I did a compression check and they were normal so that ruled out compression. That left fuel injectors. I pulled the intake plenum. With the engine off I set the throttle to WOT so I could see the actual injector stream. Since the injector rail is pressurized even with the engine off I was able to view the injector output by connecting the injector coil power with alligator clips to 12 volts. I immediately saw that the injector for cylinder 5 was shooting out a trickle compared to the strong jet of fuel coming from a good cylinder's injector. So to make a long story longer, I pulled all the injectors and rebuilt them. The main problem was the injectors have a very fine filter screen on the inlet side and they were clogged. Irritating given that I have 10 micron racor filters followed by Yamaha's 3 more (yes, 3!) filters that are under the hood before the gas gets to the injectors' 5th and final filter. How the hell they got clogged is a mystery for another day but for now I will blame the switch to ethanol. For those of you who care, the injectors are Bosch CDH240 injectors, the same injectors used on a 2002 Mitsubishi Eclipse V6 as well as a number of other cars. I got the rebuild kit (new filters + orings) from Mr Injector items - Get great deals on Fuel Injector Service Kits, Reconditioned Fuel Injectors items on eBay Stores!.

Oh - before I pulled the injectors I tried mainlining Techron into the injectors which did nothing. I am pretty sure I could have gotten away with just the ultrasonic cleaning but given the cost of the rebuild kit ($28) and the time it takes to replace the filter screens its prudent to do it.