Q: IMPELLER DWELLER
I have a 1988 2.5-liter engine and MerCruiser sterndrive with a cooling issue. After finding out my mechanic charged me for a new water-pump impeller and never installed it, I decided to make the repair on my own. I installed a Sierra impeller kit according to the Mercury repair-manual instructions. After I started the boat on muffs, it pumped water and cooled fine, but after it sat for two days, it would not pump any water up to the engine (on muffs). I pulled the lower unit and noticed I had pinched the rubber gasket for the pickup tube where it goes into the upper part of the drive. I replaced that gasket and installed another complete impeller and housing kit. I ran the boat on the muffs again, and everything seemed fine. After it sat about four days, I hooked up the muffs, started the engine, and it would not pump any water. (I never overheated the engine and never ran it at high rpm.) During all of the above, the boat was on the trailer, hooked up to the muffs, and the drive was in the down position. I tilted the drive up to the trailering position, started the boat, and it pumped water. I took it to the lake, and it ran fine and cooled like normal, but at idle, the temp would start to rise unless I accelerated to cruising speed. I’m guessing I may have overheated the impeller and/or housing by running it on the hose before tilting the drive up. Do you know of any other reason why the impeller would not pump water after it sits for a few days?
Also, when the boat is stored on the trailer, does it matter if the outdrive is stored up in the trailering position or down in the on-plane position?
I’ll answer the easy question first. The boat should be stored with the drive in the down position.
Regarding the cooling issue, a garden hose forces water up into the system, so it’s not surprising that the engine ran cooler on the hose. Inspect the base gasket between the gear housing and the water-pump base. If you didn’t replace that, you need to. Also, with the drive off, lift the bell housing (the accessory with the six bolts on it), and wiggle it up and down and side to side. There’s a water tube on the port side of the bell housing that goes up into the transom plate. Make sure it’s not kinked or does not have any holes in it.
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