Exhaust flappers...do i really need them?

davidbrooks

Yesterday I was replacing the exhaust tube and on the port engine I discovered half of an exhaust flapper stuck in the end of the exhaust.  So you fix one thing and discover something else that needs to be repaired. I know, I know "its a boat".  So my question is do I really need to fix this?  Volvo did away with exhaust flappers in 99.  Mercruiser's still have them.  I know they are there to keep water from going up too far into the exhaust.  However I have seen a lot of comments from folks that argue that you really don't need them.  Has anyone removed their flappers?  Any issues with doing that?  I thought I would ask here as I have come to respect the opinions and experience of the folks here more than any other site I have found.  Thanks in advance.

Lake_Bum

@dwolf was working on his recently and had the same question. Not sure what he ended up doing.... 

diggin2day1

When launching my boat last season, the hauling guy sent her down the ramp and into the water rather quickly. We think that water was forced through the exhaust and into the engine. When I tried to start it, at the second attempt she gave a slow crank and locked up. Had the boat towed into my slip and the mechanic checked the engine the following day.... water in the cylinders(he pulled spark plugs, drained cylinders and she started right up). Mechanic said it was one of two things- 1.) water forced into cylinders when launching down the ramp. 2.) On the first attempt to start when I stopped cranking the engine, the engine just slightly cranked backwards enough to draw water into the cylinders. Honestly not even sure if I have flappers or if they are still in tact. My engine is Mercruiser Horizon 350 and I have aftermarket(Stainless Marine) exhaust. Never had another issue all season long... flappers will be checked before this seasons launch. 

LaRea

My opinion:  I bet a quarter of all boats with flappers are missing at least one without the owner even knowing.  And I'm not aware of any rampant nationwide problem with water entry.  So, are they necessary?  No.  Is it prudent to have them?  Yes.  It's a situation of "probability is low, consequence is moderate, so risk is low."

Black_Diamond

Be interesting to get Al's thoughts. 

Handymans342

Just another thing I dont have to worry about LOL

craigswardmtb

For what it's worth a tall riser is much more important in my mind. 

J3ff

diggin2day1 said:

When launching my boat last season, the hauling guy sent her down the ramp and into the water rather quickly. We think that water was forced through the exhaust and into the engine. When I tried to start it, at the second attempt she gave a slow crank and locked up. Had the boat towed into my slip and the mechanic checked the engine the following day.... water in the cylinders(he pulled spark plugs, drained cylinders and she started right up). Mechanic said it was one of two things- 1.) water forced into cylinders when launching down the ramp. 2.) On the first attempt to start when I stopped cranking the engine, the engine just slightly cranked backwards enough to draw water into the cylinders. Honestly not even sure if I have flappers or if they are still in tact. My engine is Mercruiser Horizon 350 and I have aftermarket(Stainless Marine) exhaust. Never had another issue all season long... flappers will be checked before this seasons launch. 

This was also a possible cause of my engine needing to be replaced at least according to the insurance adjuster.  I would absolutely have all correct pieces in place, they couldn't find the flappers on mine and it was a topic of interest.. in the event of an insurance claim you wouldn't want to ever say "I didn't install the flappers" 

reneechris14

This another reason I remove drives for winter.That's right where flaps end up,and block air flow.This is also were the critters can come in.$55 and 20min work is an easy PM.

reneechris14

Oh yeah that's how you know the boat overheated at one time.

floater212

mine were bad, didn't know this then, we were skiing and the skier dropped off so we circle around quickly to make sure skier was safe and to block boats that aren't paying attention of anyone in the water and with a quick stop and shut down, motor locked up from water. not a hard fix, just an embarrassing tow back to launch! 

MarkB

I'm going to say they're important. How much do they cost? How much does a tow cost?

Handymans342

Is it possible to add riser extensions???

davidbrooks

Thanks all. You put me over the edge. Ordered two sets today. Might as well replace them all while I'm at it.

dwolf

Lake_Bum said:

@dwolf was working on his recently and had the same question. Not sure what he ended up doing.... 

Nothing yet. Im not sure flappers would do any good in my case as my boat has side exhaust with tall risers. Ive never used the rear exhaust which in most cases is where the water intrusion would come from. Best i can figure out,the flappers would be locaited after the side exhaust in the exhaust tube leading out the out drive therefore flappers in my case would only keep water from coming up through thr rear exhaust,sense ive never used the rear exhaust and the captians call cut offs completely seal off rear exhaust,seems little chance of water intrusion to me. Anyone with any info. I should know please chime in as i do not wanna take any chances if avoidable. This is only my observation which my or my not be correct.

davidbrooks

Finished up my winter projects this weekend in order to keep my launch date of March 24th.   The first one was a pain to figure out how to get the rubber boot off but after that I was able to do it without losing too many knuckles.  When I got into it all 4 were completely gone. Glad I did it.