'73 6HP Rude --- Breathing Problems

[Xcusme]

I could sure use some input on this one. My bro' in law picked up a 1973 6HP Rude long shaft. Put in the large tank and after a little choking it popped right off. Idle wasn't bad but the carb , and the whole motor was pretty dirty. I figured a good carb rebuild and impeller are in the near future for this motor with no history.<br /><br />I decarbed it and the idle improved greatly. We ran the motor in a large tank for about an hour with the cover off. At WOT in gear ,it really cranked, I mean it really turned some serious rpm's. He idled back and I replaced the cover. He again increased the throttle to WOT , but after a few seconds the rpm's dropped and seem to bog down. At first I thought the ignition was cutting out perhaps from arcing of the spark plug wires to the cover latch. I un-latched the cover and raised the cover a few inches and the rpm's took off again like normal. Since the motor did not appear to be missing , I'm guessing that the motor was being starved for air. I looked closely at the exhaust gasket and all looks good , no leaks into the cover area.<br /><br />This motor does not have a high speed needle adjust , only a slow speed needle. I adjusted the slow speed setting and it's adjusted fine and idles fine as I would expect.<br /><br />My questions is, If the carbs high speed jet was either changed to a larger size or was drilled out, would this account for the air starvation with the cover in place??<br />If the high speed jet was partially clogged, I wouldn't expect the WOT rpm's to be as high as they are now with the cover on or off. I'll guess that a high float setting would produce the same high rpm's at WOT, but it might run rich and slow things down. Anyone have any gems of advice??

 

[alcan]

Re: '73 6HP Rude --- Breathing Problems

I can't remember where this model gets air into the cowl. I think there are holes under the grab handle on the bonnet. Any way check to see that there are no rats nests or mud wasps, etc pluging off the air way. And you are correct in looking for shorts. I find this problem is most often an exhaust leak. If not the exhaust cover gasket, the the powerhead base gasket. Maybe a cracked exhaust housing. Double up the oil on a short test batch of fuel (24:1 or a little more)to make it smoke good. This may help find the leak.

 

[Xcusme]

Re: '73 6HP Rude --- Breathing Problems

Thanks for your insights. I didn't mention it before, but I sprayed the powerhead with engine cleaner and power washed it to remove all of the crud. You are right, there is an air intake under the grab handle. It measures about 1"x2.5" and it's clear. When I said I decarbed the motor, I added Seafoam liquid to 3 gals of gas with the appropriate amount of oil for a 50:1 mix. This is the fuel I was using for the 1 hour tank test/cleaning run. The motor was smoking alot. As a guess , perhaps all of the exhaust around the tank was enough to displace fresh oxygen to the intake resulting in the lowered rpm's. Omitting and shorting of the plug wires or an exhaust gasket leak, the best way to test it would be to run the motor or regular 50:1 mix and perhaps get it out on the water. <br /><br />Thanks for your help....again.