2003 175 Johnson high fuel consumption & more

Motor 2003 175 Johnson V6 carby with 350hrs and separate oil injection.
Problem
1.High fuel consumption. Expected 66 l/hr (17.5 usgph) at wot (5500rpm), get 75 using calibrated Northstar instruments. L/nm = 3.1@2500, 2.1 @4000 & 2.5 @ 5500 RPM.
2.Ragged running between 1200 & 1800 RPM under load or not. Out of the water at 1500 rpm, sounds like it is four stroking, or similar.
3.Difficulty setting revs between 2150 & 2600 under load. Changes from one to other for slightest throttle movement.
4.Oily (sooty?) deposits around motor exhausts and on grass after running for flushing. Oily deposits inside the prop. Collected exhaust water very grey and oily. Oil clings to container sides (ie not on top?). Water smells of fuel. Idling at dock leaves light dry scum on leg at water surface. Oil is Evinrude XD50
5.On flushing, port cylinder heads stabilise at 60deg C (140F) with stbd at 35 deg C at 20 deg C ambient
Other info
Fuel not stale, octane is better than required by spec. No leakage out of carbs or fuel tank. No fuel restrictions. Squeezing the hand pump during flushing gives a firm pump.
No problem starting. Maybe bit rough at idle. Has good acceleration and 31knots at 5400 RPM thru a stainless prop.
Warm engine compression (new uncalibrated tester) at wot is top to bottom 105, 105, 102 (port) 110, 111, 105 (stbd)
All head gaskets replaced recently. No report offered on bore condition but may pursue depending on responses.
Plugs and gaps good but wet with oily deposits when checked. Insulators dark brown
Spark is present on all cylinders at cranking. Strength of spark?( no judgement). No visible differences between plugs in any respect.
Boat is 1600kg (3500Lb) hard top, 21ft glass, moderate v planing with 2.5 ft pod. A previous motor was 140 v4 1.8 lit Johnson circa 88. It pushed the boat well and economically.
Question
Should I be concerned about the perceived problems and are they related.
What action do you suggest.

Re: 2003 175 Johnson high fuel consumption & more

Pull the pressure pulse/vacuum hose from the fuel pump to the crankcase, wipe the inside with a Q-tip, feel and smell for the presence of liquid fuel, presence indicates a small hole in the fuel pump diaphragm allowing additional fuel into that cyl, any excess fuel is then re-circ'd into the intake of another cyl.

Re: 2003 175 Johnson high fuel consumption & more

Oily exhaust water when flushing the engine is of no concern unless the condition is extreme. The engine is burning an oil/fuel mix so some oil film is simply a byproduct of combustion from a 2-stroke engine. Roughness at the rpm you mention (loaded or unloaded) can be due to dirty carbs or the engine may need a link&sync adjustment which is covered in detail in the service manual. Ignition timing and carb operation are closely linked so this procedure must be done properly to provide smooth transition from idle to wide open throttle. A leaky fuel pump diaphram as was pointed out can be dumping extra fuel and an oil injection pump that is metering too much oil may account for your observation of excess oil film in the exhaust. Overall, your fuel consumption is a tad over 10% of what might be expected from that engine however fuel consumption for any given motor depends a great deal on the boat weight, hull design, setup, and prop. While each of these factors can affect fuel economy, all of them or a combination of factors makes it impossible to predict exactly what you should be observing. you can measure oil consumption in relation to fuel use by marking the oil levevl on the resevoir. Run the equivalent of 12 gallons of fuel and then add oil to bring the level back up to the previously made mark. The engine should consume about 2 pints of oil which equates to about a 50:1 ratio. Oil consumption at higher rates than that would indicate an injection pump issue.

Re: 2003 175 Johnson high fuel consumption & more

Thankyou for your comments & suggestions. I can buy Evinrude / Johnson 85 to 300HP 1995 - 2002 Workshop Manual. Have not seen anything offered for 2003 on. My motor was actually built in 2002 but by motor codes (J175PXST) I gather is classified 2003. Do you think this manual (US$100 in Australia).
would be of use.
Also, I would appreciate any comments on the different head temperatures (see original posting) on port and starboard.

Re: 2003 175 Johnson high fuel consumption & more

I'm not especially familiar with that engine but I think there is a thermostat in each head. It would appear the starboard thermostat is stuck open, hence the temperature difference. As for service manuals, my feeling is that any service manual is better than no service manual although $100 sounds a little steep. Don't overlook public libraries in major cities. They may have service manuals.

Re: 2003 175 Johnson high fuel consumption & more

my suggestion is to contact a Johnson/Evinrude dealer, and get the specific, Johnson manual for your engine, no matter the cost it will pay for itself. the manual you mentioned, is too broad too many motors, and years to be specific.

Re: 2003 175 Johnson high fuel consumption & more

Try this link for the part numbers of the manuals: http://shop.evinrude.com/dyn_category.php?q=J175PXST&c=2&n=0&k=82383&x=31&y=5

Re: 2003 175 Johnson high fuel consumption & more

Grimey, Marineengine.com may have the OEM service manual for that motor.

Re: 2003 175 Johnson high fuel consumption & more

I intend to follow up on all the suggestions, however after reading other threads I have been concerned that my problem could be related to blowby or stuck rings.

Would blowby and /or stuck rings give the kind of problems I am experiencing (particularly with respect to uneven compression, fuel consumption and significant oily residues from the exhaust). Do you think it would be worth paying for a leakage test (I dont have the gear) and do these motors need regular decarbonising.

For decarbonising, can you just put an additive in the gas tank or is the aerosol spray job into the carb throats the best option. I get concerned that these sprays disolve everything they come up against if you dont do it right. Is there a risk using them and do they work?

Re: 2003 175 Johnson high fuel consumption & more

Decarboning an engine is covered in great detail in this form. Do a search on Decarb. Yes -- excess carbon can cause stuck rings, uneven compression and poor running. Using SeaFoam regularly in the fuel helps prevent carbon build up but a decarb must be done using a small amount of fuel and a large amount SeaFoam. This gets rid of the large deposits.