TOPIC: Flush Attachment 66 Johnson 40 hp RDSL-28B

I have 66 40hp and have been trying to perform a good flush after running in salt water. Initially I used a elonglated muffer type and taped over the primary intake. It seemed to work well but I recently obtained a Tempo model 91TFA which fits nicely over the primary intake but not the holes in the area circled..which allowed so much water to escape, proper cooling is not possible..no flow from the upper port. Does anyone know if there is a different flush attachment that also covered those holes?
Thanks,
John
Plantation, Fl

John,

The holes at the back of the side plate are the return line from the thermostat. Your motor recycles water when it doesn't need additional cooling. It dumps down a tube from the engine - pre heated. Some flows through a slot back to the suction side of fresh water, the rest gets dumped out those holes. OMC and Tempo once had an aluminum plate that attached to that spot for flushing. It required the two screws and the plate to be removed. An aluminum plate with a hose attachment near the forward end of the plate would be installed for flushing. These are the best type for this engine. They can be made by getting an 1/4" thick ( approx ) plate, and cutting it the shape of the cover plate on the motor now. Then drill a hole over on the left side of the plate where it aligns with the fresh water intake passage. Tap the plate for a threaded brass hose fitting - like one that would have been used to flush a vintage Merc outboard. Not easy to find a brass fitting like that locally - but perhaps online.

And I hate to say it - if you can keep her out of salt water, that would be best.

Bruce,
Thanks for the very informative response. To make sure I understand. So it's normal for water to come out of the holes until the thermostat opens which allows the water to come out of the upper port which confirms water is cooling properly? After the thermostat opens, less or no water will come out of the holes? If this is correct, I may not have let the motor run long enough to open the thermostat, erring on the side of caution. I had read about removing the side plate and tried to remove it to make a template and plate as you suggest. However, the first screw I tried to remove quickly broke. I had to tap threads for a new stainless screw but didn't try the other one. I prefer to stay in fresh water but I live on the coast in Florida where most water even in the canals and intra coastal waterway are brackish at best. I hope with a good flush, the saltwater will not cause damage. I have an advertisement on the Johnson Super Seahorse that even touts the motor as doing fine in saltwater (attached).
Regards,
John

If you have an extra muff try this. Works for a good backflush. I removed the lower portion of a muff. removed that plate and let the water flow.

That gearcase isn't that big. Can you get a plastic tub & just run it submerged?

You are correct but I like to take my boat camping and it's not convenient to haul a barrel or tub around..plus my goad is to use the original flush attachment available through Johnson.
John