Loss of RPM’s on both engines at wot

[Merkinbrumsky]

Source of the post When you replace the fuel filters, dump the fuel into a clean container and note the condition of the fuel. Look for excessive sediment, water, note the colour, etc.

Can you post engine serial numbers?

Serial # port side is A459296
I will have to check the stbd side.

[Viper]

You're on the cusp between points and their Thunderbolt ignition system. Check and see if you have points.

[Merkinbrumsky]

Source of the post You're on the cusp between points and their Thunderbolt ignition system. Check and see if you have points.

They both have the thunderbolt ignitions.

[Viper]

There were different options for carbs. If you have Mercarbs or Rochesters, they have little screen filters inside the fuel inlets right in the side of the carb. Worth replacing if you're not sure whether they've been replaced in the past. Anything that gets past the main fuel filter will eventually clog these.

[bud37]

If my memory serves me correctly, I remember Rochesters as having a power valve/piston that can create this sort of thing if the linkage in the bowl rots......just need to wait to see how he makes out with the throttle cable/venturi checks.

[Merkinbrumsky]

My weekends are Mon/Tues (awesome for a quiet marina/quiet lake) I will check/confirm all the items suggested and report back. Thanks allot to anyone who has chimed in. Although I have spent a ton of time on the water working on lakers in the wheelhouse and grew up cruising simcoe and gbay engines are my weak point and I have always let the marina work on them. Probably the only thing I usually don’t attempt first myself.

[Merkinbrumsky]

Made it up to the boat after work yesterday for a few hours. Pulled the flame arrestors, they weren’t to bad but cleaned them with some engine degreaser and the hose and put them aside to dry. Confirmed throttle plates were open all the way at wot on the sticks. I’m pretty sure carbs are the mercarbs, not 100% sure but they have a mercury tag mounted on them, and only one idle screw which is what I read distinguishes them from a Rochester, maybe that’s not correct? Any way, I didn’t have replacement screen for the carbs so I didn’t go any further there but did find that the coil wire on the stbd engine was loose. Aha, i thought. Tightened the wire and took the boat for a quick run. No joy. Back to the dock. Pulled the fuel filters and drained. Port side looked great, stbd side however was about 80% water! So I immediately started think about how to deal with this. There’s approximately 100L in that tank. Should I try and get a hose in the bottom of the tank and pump until water turns to fuel?, pump the entire tank dry?, run it and keep changing fuel filters,? Or? By the time I got the filters changed it was dark and I had to head back home for an appointment today. It didn’t occur to me until I was on the way home that I should have switched the crossover and run both engines of the port tank to test. I will get back up this week and give that a try. I have always stored both tanks full. Any ideas on how all this fuel got contaminated? What next? Thanks

[Cooler]

Fuel issues come from various reasons. I.E. Were the tanks filled with bad fuel at a marina? Did the tanks get filled with ethanol gas at some point and then sat for an extended period? Did someone at a marina pump water into your gas fill be mistake? ( That happened last year at my marina, because the dockhand was a newbie ) I would have a repair facility pump out the tank and polish the tank. Viper would be your best resource to recommend mitigation. Good luck! er

[bud37]

Yup that will do it.......the one engine not pulling it's weight. I am surprised though the engine was not running poorly as in miss firing.

Check your fuel fill port "o" ring, in reality they should be maintained regular , can be a source of water ingress especially when on a flat deck surface.

You are right , too bad you didn't run both off the good tank. On another note, it is good you checked the other things , as now they can be crossed off the list as this goes.

Oh a little edit to add....while you are there checking the o rings , if they are still the metal fill ports , check the continuity to ground ( engine block ).

[Merkinbrumsky]

Source of the post Yup that will do it.......the one engine not pulling it's weight. I am surprised though the engine was not running poorly as in miss firing.

Check your fuel fill port "o" ring, in reality they should be maintained regular , can be a source of water ingress especially when on a flat deck surface.

You are right , too bad you didn't run both off the good tank. On another note, it is good you checked the other things , as now they can be crossed off the list as this goes.

Oh a little edit to add....while you are there checking the o rings , if they are still the metal fill ports , check the continuity to ground ( engine block ).

Seeing how much water is in there I’m surprised it ran at all. I couldn’t hear any noticeable misfire. I ran both motors individually and nothing stood out. The fuel filters were done end of last summer. The marina is not allowed to open fuel tanks when they are refueling. The owner of the boat has to do that so they avoid any exoensive mistakes. I am always very aware when filling tanks. I used to own a 340 Wellcraft gran sport and a fuel dock employee filled the fresh water tank with fuel. That was an expensive mistake. The waste and water pump outs are near the stbd fuel fill cap though. They are twist off and all clearly labeled while the fuel cap requires a cap key. I will check all o rings and replace.