Re: Power Loss/Surging 2000 Mercury 125hp
I have replaced water/fuel separator and the fuel filter at the engine. The separator looked good and the fuel filter was had a lot of debris. They were pretty large pieces of some contaminate from the tank I guess. I don't know if it was enough to cause my issue or not, but will find out this weekend. I also did a compression check on all four cylinders and they all measured 125 on the guage. I am very happy at the compression results. I didn't have the opportunity to do a check before buying and was convinced when I saw the condition of the boat (exceptional) and ran the engine.
I have visually inspected plugs and plug wires, all electrical connections that I could find. I removed the front cover on carbs and visually inspected the ports with the throttle wide open using a flashlight (clean cylinders). As I stated in previous posts, the engine idles smooth and runs smooth at all RPMs unil it acts up then loses power at higher RPMs and will surge some. The first time I ran it at cruising speed to WOT for at least 20 minutes before a little loss of power. Every time after that, the power loss is more dramatic with more surging, but I can run her for at least 15 minutes at crusing speed before she acts up. That may change the next few times I use it, but I am not convinced yet that I need to pursue ignition diagnostics. I will do that next if I find there is plenty of fuel at the carbs when it is acting up.
I just got the boat from the previous owner and have only had it for two weeks. The engine only has 130 hours on it and is the original one. The boat, motor and trailer are immaculate condition. You cannot find a spot of grime, rust or corrosion of any type anywhere. It ran well the first day and the second day started acting up. Although I have just begun diagnosing this problem, I am really leaning toward fuel or fuel delivery as the cause. The previous owner rarely used it, but always winterized and rigorously kept up the yearly maintenance. He has never had to pay for a single repair and has kept it in a garage.
I plan on running all of the old gas out this weekend and filling with mid grade. If I still have problems while in the water I will take the front cover off the carbs and watch the fuel intake to see if enough fuel is making it to all four. I will probably try squeezing the primer bulb while it is acting up as recommended and observing. Can you think of anything else I should be trying while on the water testing it out?