Poor MPG Yamaha FT60

[Christiananthony]

Hi,

I am having trouble with my Yamaha FT60. Its a 2008 with 2500 hrs. Smelly exhaust, soot on the plugs and prop inner hub. Had the injectors cleaned. they were leaking before. New plugs still went black. Oil black after only a few hours. Poor MPG with a 5.5 meter rib @ 14knts.


Put the diagnostic on it. Has a history of failed MPSs and over cooling. Put the ohm meter on the water temp prob and it checks out. Cleaned out the VST filter. It was black. Fuel pressure 42psi and 32 with vacume to the regulator.

I dont think this model has a O2 sensor. Any ideas on where in the block I might be able tap in a o2 sensor so I could monitor the air/fuel ratios?


Any ideas at all would be most welcome! Thank you!


Christian
PS. Can upload screen shots of the diagnostic software while at cruise to see if someone can spot something odd.

[Nos4r2]

After 2500 hrs on a 60hp, you might want to do a compression check. Sounds like it's blowing combustion gases past the rings and burning oil.

[Christiananthony]

Hi Nos4r2,


Thanks very much for your reply and posting. Forgot to mention that; did it 140+ on all cylinders. The crankcase pipe from the valve cover does give off a bit of vapour at high rpm but nothing unusual. Oil consumption is normal.

[Nos4r2]

Not compression then. That's pretty darn good for a 2500hr 60hp!

I just noticed the 14knots part. Are you planing properly at that speed? My 5.4 won't stay on the plane til 19 knots and will drink fuel at 14 knots.

On the face of it though, it does sound like overcooling. Have you tested the thermostat?

[Christiananthony]

I have the Gemini 550 waverunner. Its about 300kg plus engine 129kg fuel, 25 kg my wife and I so say around 550kg total. Hullkoted yesterday. Yup she's and planing at about 4 degrees at 14 knots. Yes I did check the temp sender and it was OK. Ohms and fully open at 70 C.

I haven't put a vacuum gauge on yet to see if the MAP is sending the right reading to the ECU. I have however put a pot 10k from the 5 volt + and the sender wire so I can fool the ecu. Getting tricky because it "learns" (reminds me of HAL in Space Odyssey) I also put a 10k ohm potentiometer tps and am able to adjust the signal it sends back.

The same sender that reads the manifold negative pressure also is paired (beside) a air temp sender which seems to read 8 degrees warmer than it actually is. I spliced into that one and dialed it down so it read same or cooler air and the milliseconds actually went up. Which makes sense.

[Christiananthony]

Engine water temp was 65 C. which compared to a car seems chilly

[Christiananthony]

Engine water temp was 65 C. which compared to a car seems chilly

[Nos4r2]

That's probably about right-my 225 Opti runs 130 deg F (or 55deg C) thermostats.

It has got the correct plugs in hasn't it?

[Christiananthony]

Yes correct plugs direct from Yamaha in their packaging.

Going to do a test tonight; reducing the fuel pressure. Will lower pressure with a T just before the fuel rail. Will actually put two Ts one to bleed off to a gerry can I guess and one for the pressure gauge. Reduce pressure until she starts to misfire? Engine only doing 2900-3200 rpm

[Christiananthony]

Wish I knew where on (thru) the block I could put an O2 sensor.

[Nos4r2]

I take it there's no other symptoms-ie the boat isn't sluggish, feels like it's going ok etc?

[Christiananthony]

other than the rich burning problem boat is good. Bottom is like new. Hullkoted 3 days ago.

I have the data from YDS but cant seem to attach it here.