braves2629
New Member
Hello to all, I have a 1990 Donzi GT 250 with a Mercury 350 Mag Mpi. A week or so ago I was out cruising, boat was running like a top. I ran into some mud and after getting myself free I took off again and noticed that it wouldn't go over 4000 rpm when I had been running 5000+ not 5 minutes before. Boat also started to overheat over 3000 rpm. So I got it back to the launch loaded it up and brought it home. I've read forums for hours on end. I pulled my risers and manifolds and found that the port side riser water ports was clogged on both sides. I cleaned the risers and manifolds thoroughly and reinstalled them with new gaskets. This has solved my overheating issue but the not going over 4000 rpm issue still stands. I've read distributor cap, fuel issue, spark plugs/wires(which are less than 6 months old in my case). My distributor has absolutely zero signs of corrosion. While it could be a fuel issue I suppose, I just don't understand how this problem would have come about instantly after running into the mud. Boat runs like a top all the way up to 4000 rpm. No misses or shuttering, it just gets to 4000 rpm and that's all she wrote still have a good quarter throttle left but it doesn't effect anything when floored. Boat was running 50+ at 5000-5200 rpm now she'll only go about 33. I'm completely lost. I did put 20 gallons of premium unleaded right before the trip where this occurred if it helps any. Thanks in advance for any help.
