Risers rotted - But do I need manifolds too?

[Vince_nj1]

I have a pair of 6.2 Fresh water cooled Horizon engines. 340 hours / 7 years old. 2 weeks ago I started to have a rough idle with one engine. The boat ran perfect before I went for a ride, but when I came home I had a very rough idle and needed to shut one engine down. I could get the engine re-started and as long as I kept the rpm's above 1,000 rpms, The vibration would smooth out and I could drive the boat. Once on plane all guages checked out; volts, temperature, fuel burn etc. Both engines were in sync.
I wasn't sure what was causing the rough idle, so I started with the basics. I changed spark plugs, cap & rotor, wires, AIC valve and fuel filters. My neighbors complained about the smell of fuel at startup and suggested that I probably had a stuck fuel injector. I also noticed a slight hydro lock sensation at start up and thought that a stuck fuel injector in the open position might be dumping fuel into one cylinder causing the hydra lock and rough idle and once it burned off and I picked up RPM’s the engine ran smoother. I did a pressure test of the fuel system expecting it to fail and it held pressure. At this point I was at a loss so I called Doc Ron DDS to pick his brain. After talking through my issues with Ron it occurred to me that I really need to figure out why I am having hydro lock issue at startup so I reluctantly decided to start pulling spark plugs to see if I could figure out what was going on.
Well the very first spark plug I pulled was wet with water not gas. So I pulled my exhaust risers thinking I had a bad gasket. After chipping away some of the carbon on one of the risers, I poked a hole through the wall. So obviously I need to replace all of my rises. My neighbor and good friend owns a marina that allows him to get me parts at dealer prices, so I hit him up for a favor. After he spoke to his parts guy he came back with the recommendation to replace both risers and the manifolds. I didn’t want to cut corners, so I agreed and told them to order 4 of everything. I am picking the parts up tomorrow. However, this is my rub. I started to re-think the exhaust configuration. The risers are cooled with raw salt water and they failed, however my manifolds are cooled with anti-freeze and as far as I know are still good. So now I am questioning if I really need to replace the manifolds or are they still ok?
Any thoughts?

 

[rondds]

Vince
Check the mating surfaces and the coolant passages. Look in the gas passages for flaking and corrosion. I seriously doubt you'd need to replace manifolds on a closed cooling system after 8 seasons but the proof is in the visual check.

When I had my old boat I would pull the elbows (I didn't have riser blocks) every other season to replace that crappy block out gasket and give the coolant passages a looksee.

Afterthought:
Did you shoot some PB blaster or 2 cycle oil in the cylinders (at least the wet one(s)) and spin the motor? Just to keep the walls of the cylinders form rusting up?

 

[Air O'Nautical]

You prob. already sprayed the cylinders down with oil (WD40,Marvel Mystery or similar) and spun the motor to expel all water...then, your on the right track to change the exhaust parts.
No, you very well might not need manifolds if they look OK.

I personally go with 3 years on the elbow gaskets and 6 years on the elbows.
Keep in mind I'm a 6 month summer only type boater...your milage will vary.

 

[Vince_nj1]

Thanks for the feedback. In short I did not spray anything in the cylinders. I started the engine for a few seconds after disconnecting all hoses and pulling the risers. Not the prettiest approach, but I believe the cylinders are dry. I also failed to mention that I treated the fuel with 1 oz per gallon of SeaFoam 1 week earlier. So I am keeping my fingers crossed that my cylinders are OK.

 

[Chief Alen]

I believe you just need elbows.

Right now on craigs in Toms River:

http://jerseyshore.craigslist.org/boa/4624750436.html

 

[Jaay757]

I just helped change the risers and spacers on a friends 2006, 320 w/ 6.2s prior to this season. He had the same set up as you with the freshwater cooled manifolds. The manifolds were removed as we were going to also replace them. After inspection they were like new inside and out. As previously stated the mating surface on top of the manifold needs to be checked and must be good. We ended up just changing the risers, spacers and the block out gaskets.

 

[Vince_nj1]

I just helped change the risers and spacers on a friends 2006, 320 w/ 6.2s prior to this season. He had the same set up as you with the freshwater cooled manifolds. The manifolds were removed as we were going to also replace them. After inspection they were like new inside and out. As previously stated the mating surface on top of the manifold needs to be checked and must be good. We ended up just changing the risers, spacers and the block out gaskets.

That is exactly what I needed to hear. Thank you!

I knew I needed risers and after being away from the boat I was given a strong recommendation from the place where I am buying them from that I should replace the manifolds as well. I don't think he was trying to rip me off, I just think he didn't realize that my manifolds are cooled with antifreeze and not salt water. Since I didn't have an opportunity to go back to the boat to re-inspect the manifolds, I went ahead and ordered them based on his recommendation. I will be picking up the parts later today and will have that conversation about not needing the manifolds.

 

[rondds]

Vince
Spend a TON of time cleaning up the mating surface. Carefully scrape off remnants of the old gasket, use a wirebrush (on a drill) on the surface as well. Stuff rags into the manifolds prior to this to prevent crap from falling in. I also had a shop vac set up to catch all debris as it was being generated.

Then chase the threads inside the manifold with a tap so as to not get a false torque reading when you put the new ones on . I THINK it's 30 ft-lbs but double check that. And if you damage a gasket by accident throw it away and get a new one. The gasket is the weak link in the system so take good care to do everything textbook.

 

[fwebster]

Manifolds or not depends upon how much water and how long the risers were leaking. Remember that the inside of the manifolds are sitting with air in them all the time. The air that comes in from the exhaust outlet comes from right at water level so it is moisture laiden air. How the manifolds cool only addresses the water side of the casting; not the exhaust side. You can only tell how good or bad they are by removing and thoroughly inspecting them.

Ron is correct. Most manifold failures come from the failure of a seal between the riser and manifold. The Merc gaskets as so thin that it just takes a few seasons for them to dry out and "cook"......and this is yet another reason to break open the risers (Merc OEM) after the 3rd year and then every year thereafter. You have to replace the gaskets but you also get a chance to see inside the riser.

As far as whether or not your engines will survive.......probably. But your real risk at this point is the valves and heads. The water gets into the heads by running down the valve stem and around the valve head. It takes very little rust and pitting to ruin the valve guide and valve mating surface where the valve closes in the head. The sooner you get the engines back together or oil on the valves/combustion chamber the more likely you are to avoid pulling the heads and having the valves refaced and the guides replaced.

Good luck with it........

 

[Vince_nj1]

Vince
Spend a TON of time cleaning up the mating surface. Carefully scrape off remnants of the old gasket, use a wirebrush (on a drill) on the surface as well. Stuff rags into the manifolds prior to this to prevent crap from falling in. I also had a shop vac set up to catch all debris as it was being generated.

Then chase the threads inside the manifold with a tap so as to not get a false torque reading when you put the new ones on . I THINK it's 30 ft-lbs but double check that. And if you damage a gasket by accident throw it away and get a new one. The gasket is the weak link in the system so take good care to do everything textbook.

Thanks Ron.

I just off the phone with the parts guy.. It was on his recommendation that I ordered the manifolds. The exact feedback I got was "nobody sells more of these things than him and he knows what he is talking about. If I don't do the manifolds now, I will need to do it in 2 years" So naturally I agreed to the addtional ~$1500 in parts. So now I told him that I don't think I need them and he told me there is a 20% restocking fee. :smt021

 

[rondds]

Long-term undetected slow leaking inside could effect the valve seats and compression.

I was getting wafty sweet smelling billowy smoke on startup with my previous boat. It was a year for replacing gaskets and when I pulled the elbows there was coolant in the exhaust passages. When this burns off (when you first start up) that's the type of smoke you get, and I knew it. It was not enough liquid to lock up the cylinders b/c the engines started no problem. But one more season and I'd probably have busted a connecting rod or blown a hole out the side. So I pulled the heads and had them redone (after getting psi's of about 100 on the cylinders beneath the elbows). After having the heads done, the numbers were back up around 130 (other cylinders were 140).

 

[rondds]

If he sells so many why does he need to charge restocking? LOL!

Certainly nothing wrong with replacing everything. An ounce of prevention....

 

[rondds]

Definitely check compression!

 

[Bt Doctur]

Sound a bit excessive with the price for only 2 manifolds even if they are dry-joint ones

 

[Vince_nj1]

Sound a bit excessive with the price for only 2 manifolds even if they are dry-joint ones

It's actually 4 manifolds. I was planning on changing everything on both engines.

 

[Bt Doctur]

that sounds better. Try to get the SS block off plates that were used on the Blue Water series motors. This way you can use any type of riser gasket top and bottom.

 

[dpmulvey]

Thanks Ron.

I just off the phone with the parts guy.. It was on his recommendation that I ordered the manifolds. The exact feedback I got was "nobody sells more of these things than him and he knows what he is talking about. If I don't do the manifolds now, I will need to do it in 2 years" So naturally I agreed to the addtional ~$1500 in parts. So now I told him that I don't think I need them and he told me there is a 20% restocking fee. :smt021

How convenient.