HYDROLOCK 270 FV Exhaust Water Shutters

Ripple270

2002 Fv 270 Merc. 5.7 Mag MPI / Bravo 3 

I experienced the dreaded hydrolock at the end of the summer and have been chasing gremlins since. Boat is still in the water and temps are dropping, so timing is of the essence. May be towing it from the marina and onto the trailer if I can’t get it running soon. 

I have the spark plugs out, cylinders lubed (if it matters at this point), and risers and manifolds off for pressure testing and inspection. I ran a compression test and there were no major variances in all 8 cylinders. All around 130psi, but I forgot to hold throttle at WOT while performing the test, so I may need to re-perform. I initially pumped the milky oil out with a 12v pump from the oil drain hose and flushed 2x’s with fresh oil. I replaced starboard exhaust riser gasket thinking that was my corrosion / water intrusion point, only to re-assemble and discover that I was still getting water in the engine. It would run, but hard to start and very rough. I’ve replaced every sensor on the intake, rotor and cap, plugs and wires, fuel filters, etc. thinking that I had a fuel delivery issue additionally. Turns out the dead mis was tied to the continued hydrolock / fouled plug(s), or possibly engine damage. 

My question is re: lower y exhaust and water shutters. Does the boat need to be out of the water to replace these exhaust shutters? When I pulled the intermediate pipe (elbow) and hoses on both sides of the engine, water came gushing in the bilge, so I quickly replaced. Does the “wet exhaust” start at this point (lower Y pipe) or is the purpose of the water shutters? 

The plan is to flush the oil and change filter again, install new water shutters, riser/manifold gaskets (possibly new riser/manifolds), new plugs and fire to see if I have solved the water intrusion issue or if it is a head gasket/ bent valve, etc. that will require the motor to be pulled and rebuilt. Additionally, should I reassemble at this point to see if I have fixed the problem with exhaust parts/gaskets or continue on and  inspect valves, head gaskets at this point? 

Stumped and need guidance/direction on how far to proceed with the boat still in the marina slip. 

Thanks. 

GMSLITHO

I’m no expert but I would haul the boat and winterize the motor then pull the manifold and have them checked 

Ripple270

Alswagg said:

I hope you have gotten it running since the hydro locking.  This needs to be done ASAP. Along with proper oil changes.  Then diagnosis of exhaust manifold 

It has ran since initial hydrolock, but again, it ran very rough (misfire or not firing on 1 or 2 cylinders) and I’m still getting water in somewhere. The oil turned milky again after running it. I am working on getting it flushed ASAP. Where does the water usually enter the motor? Manifold/Risers? Intake manifold gasket? Head gasket? 

I am attempting to get the water issue resolved so I can re-assemble, flush oil a final time, and run it. 

Manifolds look good unless there is a crack. I’ll know more after getting them tested. Risers show gasket failure around the water jackets and may be able to be cleaned up, but probably replaced. 

Back to water shutters on the y pipe exhaust. Does the boat need to be out of the water to change them. I don’t think they are in there currently and I’m wondering if this is possibly my water intrusion point. Is the y pipe supposed to be full of water up to the shutters? 

reneechris14

It depends on the boat and load on the boat. On a 270 they right at the water line so you will have to pull the boat to change the shutter's. As for water intrusion the shutters are there to stop water from washing in when coming of plane, I don't think thats is your problem. I would focus on internal of the motor ie head or head gasket. The 350 mag should be higher then 130psi on compression. My 2002 270 was at 185psi with 800 hours on her. Test again throttle wide open then do a leak down test.

reneechris14

The leak down test will help  Diagnose valve or head gasket.

Liberty44140

Have a hair dryer with you if/when you change the shutters. night and day difference in how easy it is to remove the boot. 

rasbury

What, making your hair pretty helps?

Black_Diamond

Or....from the longest thread ever on here...the ball/check valve at the exhaust manifold. 

Ripple270

Black_Diamond said:

Or....from the longest thread ever on here...the ball/check valve at the exhaust manifold. 

Is that the 37 page thread about multiple hydrolock situations and $$$$ spent on merc mechanics swapping out manifolds, etc.? 

I’ll run another compression test@ WOT & see what I come up with. Either way it needs to come out of the water and probably into the shop. I feel like it’s a cracked head, head gasket, bent rod, etc. causing it to continue to misfire once the hydrolock situation started. The even compression somewhat eliminated those concerns initially. That’s why I kept prying into exhaust / gasket failure asan intrusion point. Boat is probably around 300-500 hours. The generator had 150 hrs. on it when purchased in 8/18. 17 yr. old boat is probably due for a rebuild, fresh exhaust either way. 

What’s a good ballpark estimate on 350 mag re-power? $3-5k? 

It ended boating season prematurely although we still slept on it on the weekends and rode with friends. Definitely not the same. I’d rather re-build this winter than have ongoing issues in the Spring/Summer next year. 

Appreciate the comments and advice. 

rasbury

Good luck and please up date with the repairs...helps us all...especially me!

Stodge

I had a hydrolock on a 350 mag this season.  Replaced it with a long block (new engine plus existing parts like intake, alternator etc.).  It ran about $12k installed.  

Ripple270

Stodge said:

I had a hydrolock on a 350 mag this season.  Replaced it with a long block (new engine plus existing parts like intake, alternator etc.).  It ran about $12k installed.  

Ouch! 

Ripple270

Stodge said:

I had a hydrolock on a 350 mag this season.  Replaced it with a long block (new engine plus existing parts like intake, alternator etc.).  It ran about $12k installed.  

Did that price include new outdrive?