Water In Risers

[regulator]

Will water migrate up through the risers and into the engine block if the rubber coating on the exhaust flappers is worn off? My 1989 Penn Yan (GM V-6) starts fine on the ears, but really cranks a long time in the water at the launch.

[lakebound88]

The flappers prevent water from purging into your exhaust manifold and filling a cylinder. This is possible but not limited to sudden shutdown of engine underway, plugged exhaust system or just plain old coming off plane too quickly while setting up shop...

Your v6 could be having back pressure problems. When you're boat is in the water you have resistance against your exiting exhaust. On muffs you will have little to no resistance.

Maybe someone else with v6 knowledge can step up.

Sent from my SCH-I545 using Lake Ontario United mobile app

[rolmops]

Think of those flappers as check valves. If they are not in good condition water will get into your exhaust system and into your cylinders. That's why those flappers are there.

On quiet water nothing will go wrong ,but with strong wave action coming up from behind while trolling you can easily find yourself stuck in the water with a bad engine,just because of those stupid flappers.If this happens it is easy for that water to seep into the oil as well.

As for your long cranking in the water, maybe you don't give enough choke when starting. Also check your points and plugs and the setting of the idle adjustment screw  on your carburetors, But the flappers have nothing to do with starting trouble. (unless you back your rig very fast down the ramp into the water)

Edited December 23, 2014 by rolmops