Leaking Riser Gasket - DIY Fail

[Jgran]

I recently purchased a 1992 Colbalt 222 with a 7.4L 454 and had it inspected by a local Mercruiser dealer. Everything checked out fine but it was noted that there was some seepage at the connections between the exhaust manifolds and the risers. The previous owner told me that he had installed new manifolds and risers the previous year. I figured that if there was external seepage, there could be internal seepage as well and it needed to be checked out. Long story short, last weekend I began to loosen the riser bolts on the starboard side before I drained the water from the manifold/riser assembly. As soon as I saw the first trickle of water on the outside, I quickly realized my oversight and drained them within 2-3 minutes while a little water continued to trickle out from the gasket area. The risers and manifolds look fine and I have cleaned the mating surface to a near perfect with a scraper, razor blade and then 220 grit sandpaper on a flat wood block to remove the stubborn spots. I read in the forums that I definitely need to use the OEM gaskets and install them dry. The new gaskets will arrive tomorrow and I am hoping to get the boat ready for the water this weekend. While reading through threads, I am getting concerned that when I loosened the riser bolts and the water leaked out that there obviously was the potential that water also leaked into the exhaust manifold and into the engine. Based on the condition of the gasket it appeared that the inner chamber was sealed better than the outter but there was definitely the potential for a little water to enter the engine. I figured that rather than cratering the engine before I ever get off the launch, I should swallow my pride and see what my next step should be. Options I have considered range from turn the key and pray, remove spark plugs and crank the engine so water has a place to go, etc. Any input would be appreciated. Any tips on reinstalling the gaskets? Thanks!

 

[HT32BSX115]

Options I have considered range from turn the key and pray, remove spark plugs and crank the engine so water has a place to go, etc. Any input would be appreciated. Any tips on reinstalling the gaskets? Thanks!

Howdy,

Welcome aboard!

Well,

You shouldn't just "turn the key"....(praying is probably ok though)

Just pull the plugs and crank it enough to purge the water. Then squirt some light oil (diesel/kerosene/WD40 mixed with regular oil etc) into each cyl and crank it again to coat the cyls , and purge any residual water (it's not salt water is it?)

Is this a closed cooled engine? (full system) if it is, you need to ensure you get the correct riser gaskets!

Otherwise, make absolutely sure you have squeaky clean, shiny flat sealing surfaces on both the risers and manifolds, and install new (OEM) gaskets.

Don't over tighten the bolts on the risers and tighten them in stages to the correct torque. (15 ft-lbs IIRC.......check the manual. it's not much.)

As soon as you get the risers installed, start the engine either in the water or with a flush adapter (muffs) to dry up ( &blow-out) any water left in the cyls, valves and manifolds . As long as you don't let it go with water sitting on top of pistons more than a few days, it won't hurt anything

Regards,


Rick

 

[Mercruiser420]

How much of a pain would it be for you to just pull the manifold and see if/how much water comes out of it? And take a look inside the exhaust ports to see if they're wet. You might not have to worry about water actually reaching the cylinders, it might just be a small amount that collected at the bottom end of the manifold. Meanwhile, you'll be putting on a new gasket and you'll know it was all done right. If your certain that water got in the motor, I'd fabricate some vacuum hose that can fit thru spark plug holes to a vacuum cleaner or something or just any pump so you can suck the water out. I'd pour a capful of marvel mystery down each cylinder. If you take the plugs out and keep cranking it don't overheat your?starter

 

[Bondo]

Ayuh,..... Welcome Aboard,..... I'd go with Rick's plan,..... Pull the spark plugs, 'n roll it over on the starter 1st,....

 

[tpenfield]

Good advice from Rick and Bondo. I'm not sure that I would pull the manifolds at this point. I'll add some comment about the 454 mercruiser. . .

The exhaust manifolds are designed such that they will hold a small amount of water internally to the exhaust chamber before it reaches the exhaust port and valve. Not much water, but a little. You may want to remove the risers again and take your flash light and see if you have water at the bottom of the exhaust chamber. The middle cylinders usually get most of the water that may leak into the exhaust, so #3,5, 4,6 cylinders. Folks who have gasket problems that go unchecked usually find valve damage and loss of compression on those cylinders.

Pop the spark plugs and give the engine a spin with the starter. If you get water spray, you will have the answer to your question.

 

[Jgran]

All, thanks for the quick and detailed response. To answer your questions Rick, it was fresh water in the risers and the engine is freshwater cooled. I haven't reinstalled the risers yet so I will definitely pull out the flashlight and see if any residual water is in the exhaust chambers as you recommended Ted. Either way, plan will be to proceed as per Rick's advice to pull the plugs and pour in some oil before cranking it to see if any water comes out.

Rick, when discussing the flange surfaces you described "squeaky clean, shiny flat sealing surfaces on both the risers and manifolds". I used 220 grit sandpaper to remove what gasket material would not come off with a razor blade. Is this sufficient or should I be progressing to 3/0 steel wool to make myself a mirror finish?

Last question, does it make sense to put anti-seize on the riser bolts to make them easier to remove down the road? I read a lot on the forums about people having trouble removing the bolts but it seemed that in most situations this was due to years of neglect of maintenance.

Thanks Again

-Joe

 

[Bt Doctur]

pull the plugs, spin the motor over, install plugs ,remove the belt from the raw water pump ,fire the motor to dry the cylinders, no more than 20 seconds
Use a fine cut flat file on both surfaces to get them smooth, install gaskets using Permatex Aviation Sealant,,install riser

 

[HT32BSX115]

Use a fine cut flat file on both surfaces to get them smooth, install gaskets using Permatex Aviation Sealant,,install riser

There are of course gaskets that should go on dry. I am a real "fan" of Aviation Permatex. But if the riser gaskets are the correct type, "they" say you're fine with them being "dry" (in fact, the SB below makes a point of saying they go on "dry")

Rick, when discussing the flange surfaces you described "squeaky clean, shiny flat sealing surfaces on both the risers and manifolds". I used 220 grit sandpaper to remove what gasket material would not come off with a razor blade. Is this sufficient or should I be progressing to 3/0 steel wool to make myself a mirror finish?

They don't have to be "mirror" finish. They do need to be flat, and clean bare metal to ensure a good seal.

All, thanks for the quick and detailed response. To answer your questions Rick, it was fresh water in the risers and the engine is freshwater cooled.

"Fresh Water " is clean clear water. When you say "Fresh Water Cooled" do you mean "Closed Cooling" (with a heat exchanger and 50/50 anti-freeze/water mix?) Or do you mean you're simply operating the boat in a lake?

It's important because the riser gaskets ARE quite different for closed cooling. (they're actually "Block-off" gaskets and you have hoses sending "raw" water from the heat exchanger directly to the riser for discharge overboard.)

In either case, the following Merc SB may apply to your exhaust system

http://www.boatfix.com/merc/Bullet/99/99_10.pdf

Looks like fastener torque is 33 ft-lbs by the way, don't know why I suggested 15ft-lb before:facepalm: I used anti-seize on my 1997 454 along with the "no-sealant" gaskets.

I also have the block-off gaskets (closed cooling) It's been 10 years and they have never leaked.

 

[Jgran]

Ok, thanks everyone for your information and knowledge. I'll hit the mating surfaces with a file to get everything down to clean bare metal and and I picked up some Permatex Aviation Sealant to be double sure I don't have a leak. The engine is raw water cooled and falls into the 4B category in the service bulletin that Rick was so nice to link to. The gaskets I ordered are part number 27-41813 which appear to be the original part rather than the newer one mentioned in the bulletin. They are the same as the ones that came out and match the hole pattern of the 27-863724 so I assume that I am safe to use them. I am planning to torque to 33lbs like mentioned in the bulletin unless someone here can explain why that wouldn't be a good idea. Once again, thanks to everyone for their input.

Joe