I am stumped AQ270 Stern Drive

[MikeCaldwell]

I am stumped, I have a Bahama Volvo Penta AQ120B with a AQ270 outboard (I am still learn the terms sorry). Im a long time mechanic building motocross bikes , cars, computers so I am capable of fixing things. But sometimes no matter how good you are there is always new stuff to learn. So, I had an overheating problem after I found out the guy I got the boat from Snapped a bolt on the thermostat and last 4 times out no 50/50 mix. I had to study the whole cooling system setup and I got most of it down. I fixed the Thermostat. But here is where I got totally derailed. I put the water muffs on and started the engine, NOTHING in the Sea Water trap, I was starting to think IMPELLER! Read a lot more, but I was not getting any fresh water in the engine, water on water muffs on! I checked hoses was about to pulle the impeller but I pulle off the house before I stuck another hose and blew in it going out of the stern with the water muffs on I expected some resistance, NOTHING! Wait a second I said, I reached down under the Stern? by the Prop and a found a HOLE! Of course I got a little happy, pulled over a 60 gallon bin (2 stacked in each other) filled it up and dropped the engine in it. I popped the top on the SEa Water filter, started the engine, and WOOSH! WATER flying out as I capped it and it filled the engine! OMG! Wait a second, my previosu 75hp 2 stroke Johnson had nothing like this just SLOTS.
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SO here is where I am baffled, manuals not helping on this older motor no one pointing this out.
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Are the SLOTS secondary in case the hole gets plugged?
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Could I plug the hole at the bottom and THEN the water would be pulled via the SLOTS or would I cause other problems?
OR Do I have a big HOLE that I shouldn't have and lots of problems now? The hole is to round to be punch in from a rock or something ;-) Help!

 

[Grub54891]

That hole is there for a reason,I just don't know myself. I suppose so it gets enough water at speed. When on the muffs, I put duct tape on the hole as a temporary plug

 

[Maclin]

It is a drain hole for the raw water intake system. Needs to be plugged when running on muffs. When in the water it is covered up and has no impact.

 

[MikeCaldwell]

So if I plug the whole and it doesn't suck the water through the muffs then I have problems right? I couldn't tell if the slots the muffs use and the hole both are using the same passage way internally up to the boat 1" inbound tube to get to the impeller. thanks for the responses I think I am ready to get it back out on the water, I ran it for at least 15 minutes and no over heating, both overflow has enough 50/50 now and heat exchanger working great and fills up as soon as I start it. Very happy, changing plugs and getting a carb kit installed before we get out there. Again Thanks

 

[Maclin]

Yes, if you have the grates covered with the muffs and the hole plugged and good water pressure it should act the way you see now. If not then impeller needs to be checked, and also there are some components in the outdrive between the intake grates and the inlet hose that goes thru the transom, they can leak and will cause suction to be lost. If those are leaking then you will have problems on the muffs, and also on plane as that part of the drive will be out of the water. Just putting around has them underwater and it will pump ok, but will lose suction on plane and overheat.

Based on your description of the exchanger filling up right away I would say your system is in good working order.

 

[jeffnick]

I tapped that hole and made a "T" handle plug for when I run on the muffs.

 

[dennis461]

The hole is the emergency intake. The gills could get covered with seaweed or trash. Forget trying to run on muffs. When on a trailer, I duct tape the gills, stick a skinny garden hose up in the hole and apply a little water pressure.

 

[MikeCaldwell]

Boy this was a while back and all is good, learned a lot since. I use a 60 gallon storage, drop the prop in and kick it on. AQ120 has both Anti Freeze internal and external which cools the Anti Freeze in the mixer unit. New thermostat and all good