MFS9.8A3 Running warm, cooling passage plugs missing?

We'll start off with the question:

Is water supposed to come out of these two holes? the smaller hole at the bottom seems like it may be a pressure bleed for the impeller pump, but the upper hole ~8mm seems like it should have a plug in it from the factory, If i put my finger over the bottom hole the flow increases out of the upper hole.




Now for the long story. This engine was originally bought for a homebuilt boat back in 2006. The builder passed away in 2007 without finishing the boat or starting the engine. I picked up the project last year and completed the boat. Ive been running it for about 6 months with no major issues, the carb never really seemed to idle that well, but it wasnt enough to bother me. Two weeks ago in Morro Bay it overheated and blew the oil fill cap off. I assumed that the 15y/o impeller had hardened up from age and bit the dust.

I got the engine home, flushed the oil a couple times, pulled the lower unit, expecting to find a blown up impeller, much to my surprise, it still looked brand new. Weird.

I put it all back together and fired her up, and she ran better than ever. except the oil pressure light was on, preventing it from going over ~2500rpms or so. I suspected the overheating event killed the oil pressure sensor, i replaced the sensor and it fixed that issue.

Next I got out the IR temp gun and checked the engine temps, unfortunately it seems like 170-180* is where it wants to run. I checked the termostat. it looked fine and opened at 140ish*, but i replaced that also, just in case.

The "tell tale" has never not pumped out a steady stream of water. However, after watching some youtube videos of other small outboards, i believe the stream could be a little stronger.

Now i have a new thermostat, brand new impeller kit, fresh oil. the engine starts in half a crank, hot or cold, but it runs at 170* at the head right near the upper spark plug. If i crank it up to 3000rpms the temp just keeps rising, i shut it off at ~200*. I have no reason to believe that there is anything clogging up the water passages. My best guess is that there is a plug missing causing low water pressure.

O... and I also have a brand new EFI Suzuki on order right now, so at this point i am just figuring it out so i can sell this motor, i don't want to pass on my problem to someone else.

Thanks in advance. Phil

Those are drain holes and are supposed to be that way. If pumping and peeing well, you probably have some blockage somewhere.

Paul,

Thanks for the quick reply. I will see what I can do to try and flush it out better. Any tips on that? I assume pull the thermostat housing and the lower unit and flush back and forth between the tube above the impeller and the thermostat output?

That sounds like a good approach. You can also use expensive salt-away.

Update! I think I finally got it. I took the lower unit off to flush the system backwards. It seemed to flow really well. Frustration was heavy at this point. Then I was examining the water pump/impeller housing and I noticed that the rubber grommet that seals between the impeller housing and the copper pipe that runs up to the engine was split in two places.

$1.46 and 3 business days later, I have a new grommet and the water flow seems to be much improved, as well as the operating Temps. It would seem prudent to inspect that grommet when doing the impeller, or possibly even replace it at the same time. For the cost I will probably do it every time I change impellers