More boat issues!!gggrrrrrrrrrrrr!!!

[LyndonH Dubai]

guys and gals
i need help from the experts
I was running my boat and she running well on Saturday
everything was fine, but then started to get a little brown smoke coming from the exhausts.
my exhaust flaps are currently missing so i could see it worse than normal and wasnt the kinda white steam you normally get
then a few mins later, the power went, and at nearly full throttle she would only maybe reach around 10mph.
we stopped here pretty quick, tried it again, she ran fine for few mins, then it did it again
i took her out of the water, flushed her out and she seemed to run fine, and when in neutral i revved her up and she sounded sweet as a nut
then when cleaning her down, i noitced we had somehow lost the fuel cap.
this could explain a lot, but has anyone had similar problems etc?
im assuming number one we were quite low on fuel, so it may and with the cap not on, the fuel wouldnt have been getting into the required area etc.
im getting it looked at and serviced and obv a new fuel cap (still not sure how the hell that happened, but hey!)
would this have caused any damaage to the engine at all?
I should have guessed, but something always happens when our family or friends come out to see us!!
any ideas please - as usual all your help is most welcome - my family of Moomba friends!
cheers:confused:

[brain_rinse]

Put some isopropyl alcohol additive in to help dry up any water that might have gotten in the tank. I'm guessing with fresh gas and a gas cap on your boat you'll be fine.

[newty]

Was the engine running hot? Sounds like an impellar problem compounded by a missing gas cap, and possibly water in the fuel.

[sandm]

replace the exhaust flaps as well.
one ill-timed reverse run and you now have water heading toward the valves... next stop-hydrolock and a new engine.

[mmandley]

Brown smoke worries me a bit, white smoke is steam from the hot exhaust reaching the cooler water, black is oil, and flue is raw fuel.

I would expect you experienced water in the fuel tank. When the engine was running with low power was it idling ruff?

Water in the fuel will cause ruff idle and also low horsepower. On the shore the engine will rev up and sound pretty decent because the engine isnt being asked for any real horsepower.

hydro lock is pretty hard for a fuel injected engine unless the water comes threw the exhaust valve or down the intake. If water is in the fuel it will just stall the engine before it hydrolocks in most cases. Not all but most. Also since these are non interfering engines < means the valves cant hit the pistons in normal operation > hydro lock is much harder threw a fuel injector.

I would replace your Fuel filter while your at it also because it will have water contaminates in it.

[sandm]

the flaps are on the rear of the boat to prevent water from coming back up through the exhaust hoses while in reverse. without them, going in reverse, especially at any speed will force water up the exhaust and possibly into the engine. that's where I was going with the hydrolock. no issues on the intake side at all from doing that unless your boat's underwater :)

[DOCDRS]

the flaps are on the rear of the boat to prevent water from coming back up through the exhaust hoses while in reverse. without them, going in reverse, especially at any speed will force water up the exhaust and possibly into the engine. that's where I was going with the hydrolock. no issues on the intake side at all from doing that unless your boat's underwater :)

I think this was more of a possibility in the older dd boats that had flow thru exhaust and did not have mufflers. On the V drives today most of the mufflers are up higher and to get the water to travel past them into the cylinders would be very very difficult under ordinary circumstances.