1979 Honda BF75 oil/gas leak?

[mikehoyt]

I have a longshaft 7.5 hp 4 stroke BF75 on sailboat. The engine was used in fresh water until 2000 and salt water since. Is flushed and usually dealer serviced every winter. I have several questions I will post independently.

1st.

In mid July this year I noticed when the motor was tilted down to running position there was a film on the water that is either oil or gas (not sure). Seemed to be quite a bit. After a while it would disappate and upon returning from a day's boating no further film would occur even after sitting overnight with motor in down position. Several other times during the year after sitting in retracted position for 1-2 weeks a similar film would occur when motor was initially lowered.

Initially had thought may be gear oil due to corrosion on leg. Upon removal from boat there appear to be no performations and the gear oil when changed last week was black and showed no signs of water.

I also checked for any obvious fuel leaks and found none around the engine itself. tank hose also seems fine. There does not seem to be any amount of fuel or odor of such around the motor itself when cover removed.

I am wondering if maybe some fuel in exhaust?

There seems to be some exhaust exiting beneath the motor under the cover on rear side - not much as most comes thru the exhuast holes on back of the leg. Is this normal and could this be an area of concern?

5 years ago when being serviced we had reported fouling occuring on lower plug only. Since then we have been running a hotter lower plug than top plug and had no fouling. This was explained to be due to wear from the pistons and just 20 odd years of use. Some oil or such getting around and the hotter plug burns it off.

Not sure what this film on the water signifies but never happened in previous 6 seasons and it cannot be good.

Engine runs well and is a fine example of why Honda outboards are my number one choice. 28 years and still reliable. I do want to determine the source of this problem though.

Regards

Mike

 

[lexi]

Re: 1979 Honda BF75 oil/gas leak?

Check fuel pump gasket is perfect and that fuel is not dribbling from here and pooling on water. I usually notice some residue about the engine as they are not absolutley oil tight.Rocker gasket can leak and oil collects in well.

Then when you sit engine perpendicular on boat it may run out of "scuppers down shaft and onto water. Oil and fuel will get by the rings into exhaust if you have leakage on one cylinder..........probably two at that age

As long as fuel or water is not dilutung oil then it may not be serious. Nice "classic " engine.

Alex

 

[JUSTINTIME]

Re: 1979 Honda BF75 oil/gas leak?

fuel pump is bad

 

[mikehoyt]

Re: 1979 Honda BF75 oil/gas leak?

A development that may or may not have anything to do with this.

Last week I changed gear oil and ruled that out.

Yesterday I moved the motor and when standing it upright black oil dripped out through the water intake screen. That can't be good but I do recall if stored incorrectly oil will drip out.

In this instance motor had been sitting handle up/prop down rather than on its side for a period of one week. Approx 2-3 teaspoons of oil in total. I would think this would have to be motor oil and come down the shaft and thru the impellor to have pooled out the screen????

Mike