Re: Flush kit for the older big twins
I think I have one of the devices you are describing, maybe a bit newer than the one FR pictured but functions the same way. I think it was for smaller hp motors, and I think mfg by Tempo. I'm recalling that I tried it once, and thought it was not worth the trouble -- would have trouble relocating it as I never used it. If you cut down one of the round flushers, or pick up one of the retangular ones (Tempo, again, I'm pretty sure), it can effectively be used over the intake above the ventilation plate on your Big Twin. You can pop off the cover plate if you want to increase water flow a little. I've used flushers on my '57 Big Twins and Johnsons, and they work OK -- motors don't overheat. Keep the rpms low, idle or the fast idle starting position. Using flushers, though, is just not the best way to go IMHO. You don't test the water pump (water pressure through garden hose will force water up into the powerhead), and to do any tuning you really need back pressure that you get only on a boat or in a test tank. My test tank is a big plastic garbage can with an outlet installed at the bottom for draining.
