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

[Lou C]

You seemed to be focused on water entering the cylinders via the exhaust . . . Maybe it is not.

You don't seem to be getting a lot of water, otherwise you would have experienced a hydrolock and the resulting damage to the engine.

Perhaps the water source is within the engine . . .

Head gasket
Valve guides
Intake manifold

Maybe a compression test, a cylinder leak test, and a cooling system pressure test are in order. (I did not see any such info above unless I missed it)

Double check the 15" height on the height of the elbows above the water line. It seems high enough to avoid water ingestion, but not sure of the spec. (FWIW - my boat - with added swim platform - has the elbows at about 12" above the water line, the spec is 13", so I'm a bit shy of the spec.)

The challenge with added swim platforms is that you can have more people at the stern of the boat and at a point further aft. So this can make the stern sit lower than the boat builder anticipated in configuring the exhaust. It does not seem like you have that issue though.

I would run the tests and if all good, see about adding a riser between exhaust manifold and elbow.

this is always a possibility, in my experience with blown head gaskets, it is more consistent than some of the these reports of water intrusion. With the just high enough elbows, or and added swim platform, the conditions have to be just right for it to happen, so it may happen sometimes and not others.
On the other hand when I had my leaking head gaskets, I found that it would consistently happen. I could run it on the water hose, shut it down and check for water in the cyls (#2 had water, #1 has just a spray of water). Right after shut down, nothing. Wait a few hrs and sure enough there it was, every time. So when the engine was hot, the gasket seemed to seal but as soon as it cooled off it allowed seepage into the cyls.
What I'd do...
if the boat is raw water cooled....get some reinforced clear hose of 3/4" inside diameter. Replace your manifold feed hoses from the thermo housing to the manifolds with this. With the boat in the water run it long and hard enough to get the engine warmed up, so the stat is open (temp gauge at about 160-165*), then with someone else driving look to see if you get bubbles in these hoses....if so that's a sure sign of blown head gaskets, or a cracked head. Combustion gas getting into the cooling water. I can up with another way to check for this with the boat on land on the water hose but same idea. Also, look under the valve covers for mayo like coating of emulsified oil. If you get this consistently with bubbles in the cooling water, time to pull off the heads after doing a compression test. If not, and this is just an occasional problem, it could be exhaust related.

 

[Lou C]

Sorry, I got risers intertwined with elbows.
Here's my boat sitting in the water with everything it normally would have on it except for people. I also found a close up of the transom assembly before we had the platform. My wife (petite) is sitting on the back. Doesn't seem to be a significant difference in how the boat sits in the water with and without the platform based on where the waterline meets the green trim. I'd estimate the platform weighs about 110 lbs.
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Here are my elbow gaskets from this morning. There's no line of rust that I can tell on the gasket, however there are what I would call specks of rust here and there inside the throat of the elbow. The opposite end of the elbow which connects to the exhaust tube leading to the lower unit looked awful though. I suspect that any signs of rust there had to come from water coming up through the exhaust or is there a level of rust which is to be expected due to moisture in the air and humidity? Should the interior of the elbows be completely void of any signs of rust whatsoever? Overall it is black and sooty. I also pulled the center spark plugs directly below the joint and there were no signs of rust on them. The plugs were replaced following the beach incident. I will be at the least changing the manifolds and elbows as it is beyond time.

What is the consensus on the quality of aftermarket manifolds and elbows? Get what you pay for or same as OEM?

View attachment 332511

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OK and looking at your transom mount, yours does seem to sit about an inch lower in the water than mine, not sure if that's enough to make a difference....
Also, while the static water line measurement is done with boat stationary, keep in mind when you slow down and come off plane, usually the bow is higher and the stern is lower, so it seems that it might be more likely than we'd expect given that our static water line is adequate at rest.

And as I said, Mercruiser has never removed flappers, from any of their models, they changed some that were troublesome but they all still have them. I never understood Volvo's logic to remove them and then do nothing.

 

[Augoose]

You seemed to be focused on water entering the cylinders via the exhaust . . . Maybe it is not.

You don't seem to be getting a lot of water, otherwise you would have experienced a hydrolock and the resulting damage to the engine.

Perhaps the water source is within the engine . . .

Head gasket
Valve guides
Intake manifold

Maybe a compression test, a cylinder leak test, and a cooling system pressure test are in order. (I did not see any such info above unless I missed it)

Double check the 15" height on the height of the elbows above the water line. It seems high enough to avoid water ingestion, but not sure of the spec. (FWIW - my boat - with added swim platform - has the elbows at about 12" above the water line, the spec is 13", so I'm a bit shy of the spec.)

The challenge with added swim platforms is that you can have more people at the stern of the boat and at a point further aft. So this can make the stern sit lower than the boat builder anticipated in configuring the exhaust. It does not seem like you have that issue though.

I would run the tests and if all good, see about adding a riser between exhaust manifold and elbow.

Thanks tpenfield. I certainly could be wrong, but I feel strongly that the water is coming through the exhaust vs the head gasket or intake manifold. The main reason I feel that way is because we'll go out for several weekends at a time for hours, pulling skiers, etc and the boat runs very well. If we anchor on flat water, we don't seem to have issues starting and running again - it really seems to just be limited to chop. I've not had issues with overheating and no signs of water in my oil or oil in the raw water. You bring up a good point that it can't be large quantities of water, as otherwise I'd damage components when starting. I'm not sure why water would be around valves guides?
I have not run a compression test recently- last time was about 180 hours ago. The boat has a total of just over 300 hours on it.
I'll double check the height of the elbows again just to be sure, but I'm leaning towards taller elbows as my existing ones need replacing anyway.

 

[Augoose]

...On the other hand when I had my leaking head gaskets, I found that it would consistently happen. I could run it on the water hose, shut it down and check for water in the cyls (#2 had water, #1 has just a spray of water). Right after shut down, nothing. Wait a few hrs and sure enough there it was, every time. So when the engine was hot, the gasket seemed to seal but as soon as it cooled off it allowed seepage into the cyls.
What I'd do...
if the boat is raw water cooled....get some reinforced clear hose of 3/4" inside diameter. Replace your manifold feed hoses from the thermo housing to the manifolds with this. With the boat in the water run it long and hard enough to get the engine warmed up, so the stat is open (temp gauge at about 160-165*), then with someone else driving look to see if you get bubbles in these hoses....if so that's a sure sign of blown head gaskets, or a cracked head.

Thanks Lou. Sounds like an easy way to test for a failed gasket or crack.

 

[Augoose]

If I go with taller elbows, how do I compensate for the increase in height so I can still connect to the old section of exhaust pipe? Do they make taller rubber couplers? I did a bit of googling but didn't come up with anything.

 

[Lou C]

What you'll need to do is measure how much more hose you need there and get a piece or have a marine supply shop cut you a piece of 3.5" exhaust hose. Might be able to buy one pre made.

 

[Scott06]

I think they make taller corresponding down elbows #17, you could use short sections of hardwall exhaust hose to make your own taller rubber couplers

 

[ripjmk]

Not to put a damper on things! But Volvo Penta Riser Extension Kit. Bulletin P-25-1-4 states that extended risers have to be used with matching exhaust "Y" pipes and are sold as kits. I guess the extension creates a different angle for the Y pipe to match. From the Bulletin I believe the kit needed would be PT# 3888846 but it is over $1k and would require engine removal to change out the "Y" pipe.

 

[ripjmk]

Thinking some more about the need to replace the "Y" pipe, I believe it has to have longer legs to keep the inlets above the static water level. Could be important if an overheat event burns through a bellow, maybe the difference between floating or sinking the boat!

 

[Scott Danforth]

first, measure your SWL to riser height.

second, like AD stated, if you were up on plane and you hydrolocked, your cylinder walls would have grenaded and you would have bent a connecting rod. so that did not happen

third, pressure test the cooling water jacket. it could be something else like Ted mentions

Fourth, if you are anchored in chop, and only then you are getting water in the cylinders. Flappers wont help in this case, you dont have enough riser height. so back to measuring your SWL to riser height.

 

[Lou C]

Not to put a damper on things! But Volvo Penta Riser Extension Kit. Bulletin P-25-1-4 states that extended risers have to be used with matching exhaust "Y" pipes and are sold as kits. I guess the extension creates a different angle for the Y pipe to match. From the Bulletin I believe the kit needed would be PT# 3888846 but it is over $1k and would require engine removal to change out the "Y" pipe.

That would be Volvo’s cost be damned engineering strategy. I bet you could make it work with the right combination of hoses, or rigid fiberglass exhaust tubing. Pull the engine to do this job? How do you say no way in Swedish!
Same company that decided you have to replace an entire driveshaft to replace u joints, an auto shop 101 level job
Same company that decided steering actuators should be non-repairable and costs $900-$1000 for the part
Same nonsense with their failure prone high and low pressure fuel pumps.

 

[Augoose]

first, measure your SWL to riser height.

second, like AD stated, if you were up on plane and you hydrolocked, your cylinder walls would have grenaded and you would have bent a connecting rod. so that did not happen

third, pressure test the cooling water jacket. it could be something else like Ted mentions

Fourth, if you are anchored in chop, and only then you are getting water in the cylinders. Flappers wont help in this case, you dont have enough riser height. so back to measuring your SWL to riser height.

Thanks Scott.
My SWL to riser height was measured and its a solid 15".
Hydrolocked might be the wrong term as the engine stopped while on plane and I took a surge of water to the back of the boat. Not suspecting anything was wrong at the time, I attempted to start the boat. It sounded awful and I destroyed the starter. I got towed in and after getting it back home I emptied significant quantities of water out of the rear cylinders on both sides. I really lucked out in that I didn't continue attempting to start the boat.
I will look into pressure testing the cooling water jacket.
Thanks for the feedback.

 

[Augoose]

Not to put a damper on things! But Volvo Penta Riser Extension Kit. Bulletin P-25-1-4 states that extended risers have to be used with matching exhaust "Y" pipes and are sold as kits. I guess the extension creates a different angle for the Y pipe to match. From the Bulletin I believe the kit needed would be PT# 3888846 but it is over $1k and would require engine removal to change out the "Y" pipe.

So I found the bulletin. Hard to follow, seems its for 2007 and newer risers?
In looking at the parts schematic (above) for my engine I've got two height options from VP - the standard riser (#1) and the 3" riser (#23). Only a single Y pipe (#20) is listed. I understand what you are saying though. I would imagine a taller rubber exhaust coupler would allow for some departure of angle?

 

[Scott Danforth]

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

 

[Augoose]

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

Hold it. Seems I measured incorrectly.
I had followed this illustration. A minus b for me is 15".


What you wrote makes sense, as the bottom of the elbow is the highest point water would need to overcome to flow into the engine? If that's the case, the bottom of the elbow bend is 3 3/4" below the top of the riser. So the highest point of my exhaust system is at 11 1/4" above SWL.
If I need to be above 14" over SWL I need to gain at least 2 3/4". My existing "standard" risers are 7 3/4" tall, so if I go to the 11.3" "tall" risers I'll gain 3.5" which is enough to put me over 14" above SWL if I understand the measurements correctly now.

Last question - if I go to the taller riser, can I make it fit with the existing Y-pipe?

 

[ripjmk]

With regard to the bulletin, Note 5 states "ail kits in this group also used for earlier engines with SX.M and Dp·SM drives". Note 5 is noted against "4.3/5.0/5.7L Ocean Series" which lists kit 3888846.
Having said that, You measured your riser height correctly the first time and as you got 15" you should be OK. Minimum is 14".

 

[Lou C]

With regard to the bulletin, Note 5 states "ail kits in this group also used for earlier engines with SX.M and Dp·SM drives". Note 5 is noted against "4.3/5.0/5.7L Ocean Series" which lists kit 3888846.
Having said that, You measured your riser height correctly the first time and as you got 15" you should be OK. Minimum is 14".
View attachment 332709

If you look at the pic of the op’s boat in the water, the water line is over the top of the outdrive right under that cap at the very top of the transom mount. Based on this diagram that puts the static water line slightly above the top of the Y pipe.
Mine might be like an inch higher and with the standard height elbows and the OE flappers I never had water up the exhaust, with the original one piece manifolds and with the later style 2 piece exhaust. My boat does have the 4.3 which is about 100 lbs lighter and no extended swim platform.

 

[Scott Danforth]

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

 

[ripjmk]

My manual does say " Load the boat as you would for normal boating"

 

[ripjmk]

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.