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2005 Johnson 175 hp 2 stroke

I

intruder44

New member
I have this outboard with 300 hours and it has low compression. My mechanic is baffled as the oil injection system is working. Not sure what to do now and looking for some advice as to rebuilding or new power head and ideas on what may have caused this?
Thanks
 
Keep in mind that compression figures will vary with cranking speed..... slow cranking engine = low psi reading. Engine must be cranking over approximately 300 rpm or higher.

The average psi readings on those models is about 95 psi on the starboard bank and 90 psi on the port bank.

You did not list what psi reading you're getting on that engine... what are they?
 
intruder44 said:
As low as 35 psi.
Click to expand...

35 psi... with the engine cranking over at normal cranking speed.... FAST?

Is this 35 psi on "ALL" cylinders? If not, what are the psi readings of all the individual cylinders?

Remove both cylinder heads to inspect the sealing surfaces of both the heads and the crankcase sealing areas.

Are the head bolts still torqued tight as they should be OR are they somewhat loose?

Did the alarm warning horn sound off with any kind of warning... and if so, what?

Describe the condition of the pistons and cylinder walls.... scored, melting down, tore up, completely dry, cylinder walls still somewhat lubricated, what?

Your mechanic being baffled is not a good sign... you may be wise to seek a second opinion if possible. Piston damage, cylinder wall scoring, piston ring damage, etc is usually caused by one or more problems such as weak ignition, VRO failure, oil restriction, air in oil line to mention a few.... also the VRO pump has been known to fail in such a manner whereas fuel (gasoline) would be pumped back into the oil tank which in time would result in an extremely lean fuel mixture.

Has the oil in the oil tank actually been checked?
 
Last edited:
Thanks, I will check with my mechanic. No alarms went on but I think there is deterioration indicating that the oil alarm should of alerted me of a problem.
 
intruder44 said:
No alarms went on but I think there is deterioration indicating that the oil alarm should of alerted me of a problem.
Click to expand...

Agreed.... There are various alarms as follows:

(VRO Horn Warnings)
(J. Reeves)

NOTE: I retired around 1991/92. Possibly some of the later V4 engines and others may also incorporate a fuel vacuum switch that would enable a fuel restriction warning to sound as mentioned below, an unknown factor to myself.

1 - A steady constant beep = Overheating - The V/6 engines, possibly some others, have a fuel restriction warning which is also a steady constant beep.


2 - A beep every 20 or 40 seconds = oil level has dropped to 1/4 tank. (Late model engine = Every 40 seconds)


3 - A beep every other second = VRO failure, air leak in oil line, oil restriction, (anything that would result in a lack of oil being supplied to the engine).

NOTE - If the warning horn is the black plastic (overpriced) three wire type horn, the warning horn should beep once when the ignition key is turned to the ON position. If it does not, it is either faulty or someone has disconnected it (a stupid move!). At any rate, if it does not beep which indicates that the horn is non functional, find out why and do not run the engine until the problem is corrected.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1


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