Hey everybody some pretty good insight in this forum, by some folks with allot of experience. Here's one for you. I have an 18ft Super Sidewinder with a '79 200 Black Max, propped with a 19 pitch SS high five. I primarily use this boat for barefooting and slalom skiing, so hole shot and mid range acceleration are the primary objectives. The boat gets used at least one evening a week and one day on the weekend minimum for 7 months. I have owned the boat for 5 years and not done any major engine work to it other than a fuel pump diaphragm and gasket. New premium plugs, lower unit oil change and inline fuel filter every season, and use nothing but 94 octane fuel and Quicksilver 2 stroke oil.
Alright, here's the skinny: Two weeks ago I'm coming back down the lake at the end of skiing where the boat has run fabulous all afternoon. Some guy comes by me in a Cougar jet boat and trims his jet nozzle up and is foolin around. So being a guy, I push the throttle down and trim my drive up after we are around 55-56 mile and hour. Tach is reading 5700 strong, max. I had the trim out to the point where there was a small tail of water lifting but nothing stupid. I ran this speed for only about a minute straight as I know this is an old motor and funny things sometime happen. Just before I started to trim back down and ease the throttle back, both myself and my passengers, heard a distinctive drone or lower tone change in the engine?? And I throttled back slowly back down to around 2800 rpm and continued to the boat launch. Engine starts fine, but when cold starting the max RPM with the throttle in full neutral position is a groggling 1100-1200 idle, where as usually I have direct and full throttle response and can rev into the 3000-4000 range, I don't do this regularly, but just so you get some background. Engine is very sluggish and slow coming out of the hole, and only will SLOWLY get up to 4300-4500 max RPM. That's down about 1200 RPM. I had to travel with work right after that so haven't really been able to look at it yet, but hope to this weekend. Here's what I'm thinking. Could I have a fouled or blocked fuel diaphram that is inhibiting low pressure and high pressure pick up and was initiated by running a little long at WOT? I have good spark (new plugs) leads are connected and solid, and the carbs appear to be in good shape. OR, have I probably dropped or cracked a compression ring in one of the cylinders? I HAVE NOT YET done a COMPRESSION TEST, but will do that this weekend. The thing is, it idles fine, there is no trace of blow by or the smell of unburnt gas or slicking behind the engine when we idle or sit after running. I would think it would idle like a pig if I was down a cylinder. Only other thing I can mention is there is a little tiny bit of steam or white colored trace in the exhaust, but only when the outside temperature drops in the evenings, thought I've seen this before.
Anyway, I've said enough, but just wanted to get the whole story out there. If anybody has any ideas that I might check out in addition to the compression test I'd be MOST APPRECIATIVE. I'd like to get barefooting again sooner than later, can't do it at a measly 39 MPH.
Cheers & Thanks,
FOOTER
1979 200 HP Mercury Black Max sudden drop in RPM/Torque
Linear Mode
