Potential hydrolock, starter on 496 mag? 2007 34PC


vmaxhp

vmaxhp

New member
Good morning. Yesterday, my starter went out. After boating for a bit, and then resting, the starter would engage, but not turn the engine. The generator had been running the whole time at rest, but I tried the parallel anyway. Same result. After a few attempts to start, the starter just spun freely without engaging the flywheel. Reading various forums, I saw some threads indicating possible water incursion from failed exhaust riser/elbows. Water in the cylinder is of course bad, and could lead to a bent connecting rod as water is non-compressible. The threads mentioned, before replacing the starter, remove the spark plugs and check for water.
Anyone have this experience? Thoughts? How can I inspect the cylinders for water?

Thanks!
 
Start pulling plugs, if one hydrolocked then there could be water pour out. Take a bit to long to pull plugs and the water (if it was there) will drain into the oil pan. If you find water, get a starter installed and crank the motor over to expel the water, then spray some fogging oil or other in the cylinders. Crank over some more and change the motor oil

Only other way to inspect for water is with a bore scope
 
Thanks. I'm going to pick up a bore scope.. good for a number of reasons. I HOPE it's just a failed starter. If not, I HOPE the only other damage is water. Have you had to replace your risers/elbows? Looks like about $2200 in parts. Ugghhh...

AllDodge said:
Start pulling plugs, if one hydrolocked then there could be water pour out. Take a bit to long to pull plugs and the water (if it was there) will drain into the oil pan. If you find water, get a starter installed and crank the motor over to expel the water, then spray some fogging oil or other in the cylinders. Crank over some more and change the motor oil

Only other way to inspect for water is with a bore scope
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No, I'm in fresh water and have never needed to replace them.

Still I would pull the plugs first to see if there is any water
 
Yup, water in 4&6 cylinders. No engine damage.. yeah! I've read in several forums that the exhaust flappers often get burned out. I was on a couple of engine parts sites and couldn't find the exhaust flapper part on any diagrams. Anyone know the part? 496 Mag base
Thanks!

AllDodge said:
No, I'm in fresh water and have never needed to replace them.

Still I would pull the plugs first to see if there is any water
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If the manifolds are 5 plus years that could be the problem. And I would replace them for peace of mind. $2200 or $12,000 for new motor.

C494DD1D-89FA-419C-9C81-3D0ED4C30815.jpg
 
Thanks. Just the manifolds, or, manifolds, riser, and elbow? I also see there's an elbow standard and a 2" rise elbow. Not sure which I have. Eng ser is 0w676269

Admin said:
If the manifolds are 5 plus years that could be the problem. And I would replace them for peace of mind. $2200 or $12,000 for new motor.

View attachment 8600
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I really recommend you disassemble prior to ordering everything.

When I replaced the manifolds on my 496 I found the elbows were perfectly fine. No risers to replace. So I saved a bunch of money re-using the perfectly good elbows.
 
That makes sense, thanks. Is disassembly fairly straightforward? I'm fairly mechanically inclined. Can it me done in the water?
Thanks!
Rick

HellRaZoR004 said:
I really recommend you disassemble prior to ordering everything.

When I replaced the manifolds on my 496 I found the elbows were perfectly fine. No risers to replace. So I saved a bunch of money re-using the perfectly good elbows.
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I want to better understand the potential issue with the internal flappers. Are we saying that when the boat comes off plane, that the water can rush through the external flappers, through the exhaust elbows and pass through the failed internal flappers? If yes, where does the water go after it penetrates through the internal flappers?
 
As a boat mechanic described to me, if you chop the throttle and the wake catches up to you, that can force water back through the exhaust if the flappers have failed or burned out. If the water reaches the exhaust manifold, the water can be sucked into the cylinder(s). If that happens, water doesn't compress like air and you can have a catastrophic failure.

FTL_Alan said:
I want to better understand the potential issue with the internal flappers. Are we saying that when the boat comes off plane, that the water can rush through the external flappers, through the exhaust elbows and pass through the failed internal flappers? If yes, where does the water go after it penetrates through the internal flappers?
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If your boat as the stainless steel riser elbows you don’t need to replace those. You will need the turbulator plates and gaskets to go under those elbows after you do the manifolds.

Yes this job can be done in the water and I think it’s easier since you don’t have to haul the manifolds up-and-down on the ladder.

I have seen a few PCs that the exhaust flappers were missing on and probably for more than one season. Sometimes Flappers get caught in the exhaust port in the transom assembly I’ve noticed when doing Bellows . Otherwise if you’re not looking you won’t notice them caught in that spot. None of these PCs had any water intrusion from the flappers it was all from the manifolds. Not saying it’s not possible Very poor design on the flappers the picture attached shows the older and the newer . Older has that stainless steel piece on each side.

And I never totally cut the throttles I always come to a stop very slowly and wait for the wake to level out and or catch me before I drop to Idle .
 
As suggested, I'm going to take the exhaust manifolds, risers, and elbows, off and inspect before I order parts. I took a US Power Squadron On The Water Practical Skills course and one of the best practices noted in the course was to turn 90 degrees as you're chopping the throttle so the wake doesn't catch the boat aft.

Admin said:
If your boat as the stainless steel riser elbows you don’t need to replace those. You will need the turbulator plates and gaskets to go under those elbows after you do the manifolds.

Yes this job can be done in the water and I think it’s easier since you don’t have to haul the manifolds up-and-down on the ladder.

I have seen a few PCs that the exhaust flappers were missing on and probably for more than one season. Sometimes Flappers get caught in the exhaust port in the transom assembly I’ve noticed when doing Bellows . Otherwise if you’re not looking you won’t notice them caught in that spot. None of these PCs had any water intrusion from the flappers it was all from the manifolds. Not saying it’s not possible Very poor design on the flappers the picture attached shows the older and the newer . Older has that stainless steel piece on each side.

And I never totally cut the throttles I always come to a stop very slowly and wait for the wake to level out and or catch me before I drop to Idle .
Click to expand...
 
To make manifolds removal easier. Get some 3/8-16 all thread rod from the hardware store. Cut them in 4 pieces about 6 inches or so. Remove the 2 bolts on the ends, then install all thread. Remove the rest of the bolts and slide the manifolds off. To reinstall, either get exhaust gaskets with the end bolt holes noticed out, or notch them out your self. Install mans, then slide gasket in. Finish as required.

Torque to 26 Ft LB
 
Thank you sir! Where can I find torque specs for manifold (26 ft lb as noted), riser, and elbow?

AllDodge said:
To make manifolds removal easier. Get some 3/8-16 all thread rod from the hardware store. Cut them in 4 pieces about 6 inches or so. Remove the 2 bolts on the ends, then install all thread. Remove the rest of the bolts and slide the manifolds off. To reinstall, either get exhaust gaskets with the end bolt holes noticed out, or notch them out your self. Install mans, then slide gasket in. Finish as required.

Torque to 26 Ft LB
Click to expand...
 
There in the manual 30

Note torque is using clean threads, not rusted or corroded ones. So if you see these issues, chase the threads with a tap first

496.jpg
 
Yes, it first gen and still over 6mb, so is normally an issue.
Pm me your email address and I'll give it a try
 
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