[omc-boats] problem solved

Some of you may remember my post several weeks back about my 69 Rogue V8 that had no power on acceleration above 1000rpm. I think I found and solved the problem. I first got a little delay from hurricane Charley that passed right over Marion,SC! First, I replaced points, plug wires, condensor,coil,rotor and distributor cap. That not solving the problem I kept the old parts which should still be useful. I rebuilt the carburetor. No luck. I checked the carb. to intake manifold gaskets. Nope! About this time I ran across something in one of my manuals ( I think it was the Clymer ) on vacuum testing. I had not done this and gave it a try. First I got online and learned about engine vacuum and how to test it. I went to the NAPA store and bought a plug that screws directly into the hole along one of the runners of the intake manifold to draw a true vacuum reading. This plug had a nipple end that I plugged my vacuum gauge to. These gauges are fairly cheap. I cranked the engine and the needle was swinging wildly between 0 and about 15. It seemed to read "late valve timing" - I figured what does that mean? Back to the internet for a lesson on engine valve timing. At this time I was thinking - did the timing gear get off somehow? Anyway I decided to adjust the valves one more time. A mechanic friend of mine said that most people turn the valves down one quarter rather than the full turn as described in the literature. I went in to recheck the valves. I pulled the odd valve cover off first and proceeded to back off the valves to 1/4 turn. I would loosen till they chattered and then slowly tighten to 1/4. I finished the odd half then went to the even side beginning with #8 then #6 and at this time the vacuum needle still hadn't changed. When I did #4 the needle leveled out and by the time I had done the last valve of cylinder #2 the needle was steady and up into the normal range and you could tell a noticeable improvement in idle. I still don't quite understand what went right but I will use the vacuum gauge more often when I test and tune. I also did not use any of the ports off the carb. to test the vacuum which I think may not give an accurate reading. They say you can use the rear port that usually hooks vacuum to a PC valve or to a brake master cylinder but I had no such port on the back of the Roch. 4 barrel. Maybe because it is a marine carb. or pre-emission model? The more I worked with these valves the more I came to respect them and the effects they can have when out of adjustment. I don't know how I got them overtightened initially but suspect that I was trying to go too fast and not allowing them to bleed down during adjustment. Anyway I hope this will help someone someday when they get a similar problem. Now if I can get to the river before hurricane Frances hits his weekend! Tom K.
Received on Wednesday, 1 September 2004