Q: On my OMC Cobra upper gearcase, I removed a plug on the side and the piece holding it in fell into the housing.
What can I use to seal up this hole – and can I leave the piece inside the case?
A: The piece does not need to
be removed; a sheet metal plug can be made up and installed with 680 retaining compound or an epoxy compound. *Note –
there is only 14lbs pressure on this plug.
Q: What direction do I install the Cobra water pump impeller into the housing?
Remove the top plastic cover, and the 3 bolts on the water pump housing. After removing the housing, you can then install
the new impeller kit. Install impeller in either direction as it will correct itself once the shaft starts turning. Make sure
to grease the impeller with bearing compound (lithium grease), slide it back onto the water pump shaft and push the housing
onto the gearcase until the 3 bolt holes line up. Install the bolts. Remember to use a gasket compound when installing the
seal and gasket on the back of wear plate to prevent air from entering the pump.
Q: Oil is leaking from my OMC outdrive
lower unit – what seals need to be replaced?
A: The unit needs to be first pressure tested. A 50% - 50% soap –
hot water mix should be sprayed on the propeller seal to see if that is where the leak is coming from. Make sure to spray
both sides of the gearcase as well to check for any cracks. If no leak can be seen, then the upper seal or the shift is most
likely the cause of the leak. *Note – the lower unit must be removed and the shift cable must be capped to pressurize
Q: How can I tell if I need to replace my u-joints?
A: You'll feel a vibration coming from the outdrive
when turning. This vibration can also be caused by the gimbal bearing starting to fail. A visual inspection of both are required.
Why does my exhaust bellow have holes down one side where as my original one did not?
A: The new design with the holes
helps alleviate some of the back pressure to reduce the carbon buildup in the engine crank case. This is primarily caused
when trolling at low RPM. The engine crank case bearing would tend to seize due to carbon buildup. The modification on the
bellow was made in later years by OMC.
Q: Will the updated detent in the lower unit help make shifting easier?
Yes, the updated detent will make shifting smoother. It has a differently angle and has an accurate centering spot for adjusting
placing the shifter in neutral. *Note - shifter rod should be screwed in 7 - 8 turns. This is approximately 7.156" in
height from the top of the base cover to the top of the shifter when in neutral.
Q: I installed a new impeller and a
new thermostat but my engine is still overheating. What else can I do as my engine is still overheating?
A: Make sure
that the impeller is still in good shape, and that gasket compound was used on the gasket and o-rings on the case. Next, it's
possible that exhaust gas is escaping through the manifolds into the water passage and causing a pressure buildup of 60 -
80 lbs from the engine exhaust, preventing the fresh water from being pumped through. The exhaust manifold needs to be tested
by plugging it at one end - and hooking the other end to 15 lbs air pressure. Listen for any air leaks. The area that gets
plugged would be where the water comes out of the manifold, and air gets injected where the water enters the manifold. There
should be no air leaks. This is the second most common cause for overheating.
Q: How do I know if I need to replace
my gimbal bearing?
A: The gimbal bearing (part 3853807) will make excessive noise when turning left or right. It will
also cause vibration in the outdrive. In some cases, if water has penetrated the gimbal bearing through a leak in the u-joint
bellow, the engine may not turn over until the outdrive is removed.