Exhaust flappers

[Dan01543]

So I have a 1996 wellcraft excel 21sl boat with a volvo penta 5.0fl motor. When I did my gimbal bearing and bellows I noticed these 2 oval looking rubber pieces in the bottom of my y pipe for the exhaust. I guess they are my old flappers. I bought new ones but I also read somewhere not to put those flappers in as volvo penta sent out a service bulletin about not replacing them. So if I don't replace them or put the new ones in won't I hydro lock my motor coming off the throttle when entering a no wake zone or the marina were my slip is at.id like to know if I need to install them or if I'm okay with not running them. I got a new exhaust bellow In place so my exhaust is going out the propeller. So my question is do I install them or do I not and get my money back. Thank you dan

 

[Scott Danforth]

covered about 200 posts. not needed on Volvo Penta

 

[Dan01543]

What about as far as hydro locking my motor because of the pressure of water getting up into the y pipe and then water getting into manifolds

 

[Dan01543]

I was told I could hydro lock my motor if the flappers are not in place. So I just wanted to make sure I'm ok

 

[Horigan]

Leave them off. Lots of successful boaters out there without them. Try to avoid slamming the throttle to idle when on plane and you'll be successful also.

 

[Lou C]

If you have any doubts try to measure the static water line of the boat with it in the water, you need the tops of the elbows to be 12-13” above that. I have those same OMC designed flappers in my Cobra (Volvo simply adapted the whole Cobra transom mount for the SX series) and as long as you don’t overheat the engine they are fine. But if you want to leave them off make sure your elbows are tall enough. If not Volvo makes taller elbows & there are spacer kits as well.

 

[Scott Danforth]

I was told I could hydro lock my motor if the flappers are not in place. So I just wanted to make sure I'm ok

regarding hydro locking..... you are OK there.

you have a volvo (not thru-prop exhaust) so your chance of hydrolocking is so signifcantly less than a mercruiser with thru-prop exhaust.

 

[Lou C]

I could be wrong but I think the single prop
SX has thru the prop exhaust and the SX/DP has the exhaust housing on the lower unit....

 

[Horigan]

That's correct. Thru prop on single SX drives.

 

[Lou C]

Yep just like the Cobra in that respect

 

[Dan01543]

regarding hydro locking..... you are OK there.

you have a volvo (not thru-prop exhaust) so your chance of hydrolocking is so signifcantly less than a mercruiser with thru-prop exhaust.

I have a thru prop hub exhaust. My exhaust comes out in the center of my propeller