Home › Forum › Ask A Member › OMC 9.9 / 15 impeller housing related questions › Re: OMC 9.9 / 15 impeller housing related questions
Unfortunately, you can NOT use the larger grommet on your engine, even though it sure makes installation much easier, you must use the grommet on left (shorter one).
I just happened to prove this to myself last year! The taller grommet, when used on engines with the sealed exhaust megaphone (like yours), seals up the "wall of water" drain. I tried the taller grommet and quickly found out that water was trapped between the exhaust housing and the inner exhaust tube when the engine was tilted up/pulled out of the test tank. This trapped water could find its way back into the powerhead, especially when the engine is removed from a boat and loaded into the trunk of a car/truck bed.
The taller grommet (one on the right), is used only on 9.9/15s with the open exhaust megaphone.