90 hp Mariner Question

[rsh19904]

Well I went out and bought a little 15' bass boat with this motor on it..motor is an 87 and freshwater use.  The person who I bought it from said that after winterizing 2 seasons ago he popped the cover off and saw that the 1 gal. oil tank (its mounted on the motor) had leaked down to empty..he told me the motor was in the "down" position for the winter and didn't bother with the leak due to using the trolling motor..

my question is does anyone know what my have caused the leak?  I saw the cap and it looks like the oil came from the cap area and ran down the front of the tank to the underside of the motor?  I can't see any cracks and the lines are all hooked up..but I haven't taken off the tank yet..any suggestions on where to look..wanna keep this boat as a putt-putt for the days I get the sweetwater itch  

[GoneFission]

If it's a Mercury, check the oil tank cap carefully.  Some people get them too tight (too tight = broke) and it cracks the top of the cap.  Oil will then run out through the crack in the cap.  Almost all Mercury dealers stock the oil tank caps because so many get broken.  

Hope this helps - see ya on the water!

[JimCt]

I'd pull the tank off completely and bench test it for leaks.  If the tank is completely empty there may be a leak somewhere else too besides the cap.

[rsh19904]

Thanks guys..looks like the cap leaked but didn't see any cracks..what's a good way to pressure test the tank?  is there a cap you can buy that will work or just tape the air hose to the opening and use duct tape over it and listen for leaks?  unfortunatly the bad weather up here and temps in the low 30's aren't too conductive to working on my toys      hey it should be in the low 50's by early next week..good enough  for me..

[JimCt]

To test it after you've pulled it from the motor, plug any openings and fill it with water.  Dust it with baby powder and any leakage will show right up.  Before re-mounting be sure all water is out and it's bone dry inside.

[rsh19904]

Cool..will do.      I'll check the hoses for any dry rot too and see what's up..also read that  you've gotta purge the air from the oil injection unit prior to firing up..sound about right?

[JimCt]

Yup.