Hydrolock, swim platform, riser height and static water line question

[bruceb58]

Your manifolds and risers look fine. I assume this a freashwater only boat? I would not bother with a flapper at all. My boat sits just as deep as yours in the back and I have had very large waves hit the stern and never had the same problem as you are having.

 

[Lou C]

Well regardless there is definitely a problem, and I'm wondering if when the boat comes off plane, water rushes up over the ESP and the leverage of it pushes the stern down more than if it wasn't there, thereby pushing water up the Y pipe under certain conditions. That's why I suggested ditching the exhaust bellows and putting a flapper over the 3.5" hole in the gimble housing.

 

[Augoose]

agree with you @Lou C . wondering where the SWL is when there are 5 people sitting on the swim platform.

Scott,
just to clarify, since this issue first occurred and for the entirety of last summer, we've stopped sitting on the back of the boat completely when anchored because of this issue. With that said, there was one day last summer when we were anchored in chop (no one on the platform beyond getting in/out of the water one at a time) and we still took on water in the rear most cylinders on at least one side, maybe both (can't recall). That day, I attempted to start the boat, it wouldn't start and didn't sound right. I immediately disengaged the starter and pulled the plugs - the plug was wet and a bit of water came out. This only occurred one time (and we went out about every weekend last summer) but we are so worried now my wife runs the kids off the back of the boat and no one enjoys the swim platform at all.

With the measurements I posted above, do you recommend taller risers?

 

[Augoose]

Your manifolds and risers look fine. I assume this a freashwater only boat? I would not bother with a flapper at all. My boat sits just as deep as yours in the back and I have had very large waves hit the stern and never had the same problem as you are having.

Thanks Bruce,
the boat spent its first 120 hours in brackish water in Florida prior to my ownership. Since then, I've had it in freshwater with over 300 hours now.
In examining the passageways of the manifolds, they look pretty obstructed from what I could tell with chunks of flaking rust. While I was not having overheating issues, one riser did feel a bit hotter than the other but not so hot that I couldn't keep a hand on both while the engine was running. Engine temps always were within SM range.
I was thinking about replacing them out of an abundance of caution, but I don't want to throw money away either. My concern is that my photo might not adequately capture the condition of the manifolds?

Thanks!

 

[Augoose]

Well regardless there is definitely a problem, and I'm wondering if when the boat comes off plane, water rushes up over the ESP and the leverage of it pushes the stern down more than if it wasn't there, thereby pushing water up the Y pipe under certain conditions. That's why I suggested ditching the exhaust bellows and putting a flapper over the 3.5" hole in the gimble housing.

Thanks Lou - just to confirm so I don't mislead anyone, I've never had water come in through the exhaust while the engine was running. With the surge incident coming back from the beach, the engine stopped suddenly and then the wave of water hit and came up and through the exhaust. I believe the issue which caused the engine to stop has been solved and is likely separate from what's occurring now.
Now when the boat sits anchored with the engine off while we are swimming, if a boat passes by and causes a large enough wake or chop, I seem to run the risk of taking on water in the cylinders, possibly due to water making its way up and through the exhaust. No evidence of water in the oil and the boat has run great all summer if only subjected to flat water.
If Scott is correct in his measurement instructions (not saying he isn't, there just seems to be a lot of miss-information out there about how to measure the SWL) then taller risers might be my solution as the highest point of my exhaust is 11.25" above the SWL. Doesn't necessarily explain how we haven't had a problem until now since we've had the swim platform since 2016, but maybe we were just lucky or didn't hit the combination of a full fuel tank, gear in the back of the boat vs the front AND chop. I really am at a loss for what's going on here.

 

[alldodge]

If the boat is not sitting lower from years ago then there should be no issue. Only reason for it to sit lower is weight

Edit: Unless there is part of the inside of the elbow which has worn away

 

[alldodge]

Like this

 

[bruceb58]

Thanks Bruce,
the boat spent its first 120 hours in brackish water in Florida prior to my ownership. Since then, I've had it in freshwater with over 300 hours now.
In examining the passageways of the manifolds, they look pretty obstructed from what I could tell with chunks of flaking rust. While I was not having overheating issues, one riser did feel a bit hotter than the other but not so hot that I couldn't keep a hand on both while the engine was running. Engine temps always were within SM range.
I was thinking about replacing them out of an abundance of caution, but I don't want to throw money away either. My concern is that my photo might not adequately capture the condition of the manifolds?

Thanks!

If that's the case, you my possibly want to replace the risers at least. I believe in only buying OEM manifolds/risers. When DonS was still here(RIP) he also only used OEM.

 

[Augoose]

Well this blows my theory out of the water! Attached is a page from the newer 5.0 GXI-P manual. Although it shows a better way of testing static water level, it also clearly shows a water level ABOVE the "Y" pipe! It also says load to maximum capacity.
I would test it per this latest page and if it is 14" or higher say it's good, if not do something about it.
View attachment 332720

Thanks for the illustration!

 

[Augoose]

If that's the case, you my possibly want to replace the risers at least. I believe in only buying OEM manifolds/risers. When DonS was still here(RIP) he also only used OEM.

Thanks Bruce.
I've been around here long enough to remember Don S and he was an amazing resource.

 

[Augoose]

All,
I'm about to order new risers and I'm trying to decide between taller risers (where I will need to cut fiberglass to make them fit) or go with the same height I currently have.
Scott Danforth indicated that I should measure from the bottom of the elbow bend.

15" should be good to go. you are measuring to the bottom of the elbow bend, and not the top of the riser, correct?

However, this illustration posted by ripjmk shows the measurement at the top of the riser.



If measured from the top of the riser, I'm at 15" above SWL. If measured from the top of the elbow bend, I'm at 11.25" above SWL which indicates that I will need taller risers as I'm below the 14".
I'm leaning towards taller risers but I just want to be sure before I start cutting fiberglass.
Thanks

 

[ripjmk]

All I can say is that I have never seen any manufacturer written instruction telling you to measure anything other than the distance to the TOP of the riser.

 

[Lou C]

Yep that's what I've seen in both Merc and Volvo documentation. Measure from the top of the elbow.

 

[Augoose]

Thanks guys for all the help and advice.
Since trimming a bit of fiberglass is the only downside to installing taller risers, that's what I'm going to do. Cheap insurance since they need to be replaced anyway.

 

[Bondo]

Thanks guys for all the help and advice.
Since trimming a bit of fiberglass is the only downside to installing taller risers, that's what I'm going to do. Cheap insurance since they need to be replaced anyway.

Per our pm, when goin' to taller risers, sometimes the angle is steeper to the y-pipe,.....
Other times, just a longer rubber connector might be necessary,......
Never seen the need for a different, taller y-pipe though,.....
Good luck with it,....

 

[Augoose]

Per our pm, when goin' to taller risers, sometimes the angle is steeper to the y-pipe,.....
Other times, just a longer rubber connector might be necessary,......
Never seen the need for a different, taller y-pipe though,.....
Good luck with it,....

Thanks Bondo.
I have found 3.5" ID wet exhaust softwall hose. Hopefully that is correct for this type of application.

 

[Augoose]

My OEM parts are coming in. Here's one of the mating surfaces on one of the risers. There is a gouge on one inner surface which is significant enough to catch a fingernail. Will this be an issue?

 

[Lou C]

I would not use that, those are Volvo OE?

 

[Lou C]

looks like this was dropped after machining, I see a chunk taken out and some dings in the sealing surface...I'd send that back.

 

[Horigan]

looks like this was dropped after machining, I see a chunk taken out and some dings in the sealing surface...I'd send that back.

... or take it to a machine shop to clean up the surface. Could be less hassle than returning it. Maybe the supplier will pay for the machining.