Should I replace These Risers?

[pyrotek]

Hi All,
I have a lot of corrosion on the starboard manifold. Previous owner said he replaced risers and manifolds ~3 years ago, but I think he only replaced risers. I NEED to replace the manifolds and possibly the risers. I think there was a leak between the manifold and block which caused severed corrosion. Three bolts are rusted out and the bolt heads are too corroded or rounded to remove. Hopefully drilling them out will work. Any suggestions here are welcome.

But, my main question is should I replace the risers or can I get away with another year or two? These are all Mercruiser parts. I plan to buy Osco. Hopefully using the Osco manifold and gasket and Mercruiser Riser is compatible. The other side is not pulled but appears to be in slightly better condition.

Thanks

 

[TilliamWe]

Re: Should I replace These Risers?

The water jackets of those risers looks fine to me.

 

[achris]

Re: Should I replace These Risers?

If you plan on changing both manifolds and elbows, why not update to the newer 'dry-joint' system. The manifolds and elbow last a lot longer and there is far less risk of corrosion dumping a load of water in the engine oil... If you want the part numbers for the dry-joint manifolds let me know. From the look of the manifold I assume that engine is a BBC.

Chris.....

 

[Don S]

Re: Should I replace These Risers?

I see nothing wrong with that riser, why do you want to replace them. What kind of a problem are you having? Don't just start throwing parts at a problem for no reason.

 

[pyrotek]

Re: Should I replace These Risers?

I should have mentioned that two of the water jackets were almost sealed when I took it off. I had to scrape it off. I had a few 1 inch flakes come out. There are a couple small pieces still knocking around in there. I haven't tried to run water through it yet to flush it out.

I don't know of if Osco manifolds are ok to use with Mercruiser risers. Would it be better to use Mercruiser assuming I can find them? I heard they are hard to find. Any suggestions who carries them?

Don't know what BBC engine is. It's 454 '97 carb. I can't find the "dry-joint" system in aftermarket products. As long as the initial water jacket blockage is ok, it sounds like I will only replace the manifold, so dry-joint may not be an option.

 

[pyrotek]

Re: Should I replace These Risers?

Ok, maybe the "blockage" is normal. I'm looking at the new riser gasket. Some have a very small "vent" hole on the sides, and only two large openings for the water?

 

[achris]

Re: Should I replace These Risers?

...I don't know of if Osco manifolds are ok to use with Mercruiser risers. Would it be better to use Mercruiser assuming I can find them? I heard they are hard to find. Any suggestions who carries them?

Merc elbows should bolt straight onto Osco manifolds.

Don't know what BBC engine is.

Big Block Chev, 454, 496 etc.

It's 454 '97 carb.

That's a BBC....

I can't find the "dry-joint" system in aftermarket products. As long as the initial water jacket blockage is ok, it sounds like I will only replace the manifold, so dry-joint may not be an option.

You won't find dry joint manifolds or elbows in aftermarket yet, still not enough of them failing yet to support the AM people doing them, which is a good indicator of how long they last...

Chris......

 

[pyrotek]

Re: Should I replace These Risers?

Should the bottom of the riser be silver as shown in the pics or do I need to sand or scrap more gasket material off?

 

[sjohnson44]

Re: Should I replace These Risers?

That may be just residual material from those gray gaskets. They almost have a graphite feel to them.

I had a buddy at work clean mine up and stick it on a granite to check the flatness of them and they were fine.

An SOS pad would clean them up fine.

Just throwing this out there, don't the OEM manifolds have provisions for using them on dry joint or wet? Just saying because my new ones have plugs on either side of the riser mount. BBC's may be different, but if they aren't you could always reuse those risers and when it is time to buy risers convert to dry joint and then you will only have to buy risers. Hopefully I went in the right direction with that, just taking from personal observation.

 

[tpenfield]

Re: Should I replace These Risers?

I should have mentioned that two of the water jackets were almost sealed when I took it off. I had to scrape it off. I had a few 1 inch flakes come out. There are a couple small pieces still knocking around in there. I haven't tried to run water through it yet to flush it out.

I don't know of if Osco manifolds are ok to use with Mercruiser risers. Would it be better to use Mercruiser assuming I can find them? I heard they are hard to find. Any suggestions who carries them?

Don't know what BBC engine is. It's 454 '97 carb. I can't find the "dry-joint" system in aftermarket products. As long as the initial water jacket blockage is ok, it sounds like I will only replace the manifold, so dry-joint may not be an option.

If you want to see some crap risers, I should post a few pictures of the ones I just replaced.

Keep in mind that on the 454's they often use a flow restricting gasket between the riser and manifold. When you take it off, it will looked mostly blocked on 2 sides, as you mentioned.

Unless the manifold mating surface is dramatically worse than what is shown, I think your manifold & risers are fine.

BTW - I replaced with Barr brand, but could have gone with either Barr or Osco; they both "Google" well.

Also, in picture #5 . . . that little 'pee' hole showing in the bottom of the riser . . . make sure you clear that out. It will drain down the riser a bit further after the engine is shut off . . .

 

[pyrotek]

Re: Should I replace These Risers?

Thanks Ted for the info. Your website was a great help. I'm about to inspect the rest of the engine. I think some of the cylinder heads screws and engine mounts aren't looking to great due to the manifold leak. I'll take pics when I get the manifold off.

Should I expect to do any other maintenance once the manifolds are off and I have access? I plan to clean as much as the bilge as I can. I see you also noticed rust on the cyclinder wall, so I'll check that as well. Not sure I can turn the engine over with outdrive installed. Should I unplug the drain plug to try to get rid of sediment? I see you took a power washer to it.I might be able to rig a small hose into it. It's been stored with antifreeze over the winter (hopefully!).

 

[sjohnson44]

Re: Should I replace These Risers?

I would say general clean up and maybe change spark plugs?

 

[tpenfield]

Re: Should I replace These Risers?

Thanks Ted for the info. Your website was a great help. I'm about to inspect the rest of the engine. I think some of the cylinder heads screws and engine mounts aren't looking to great due to the manifold leak. I'll take pics when I get the manifold off.

Should I expect to do any other maintenance once the manifolds are off and I have access? I plan to clean as much as the bilge as I can. I see you also noticed rust on the cyclinder wall, so I'll check that as well. Not sure I can turn the engine over with outdrive installed. Should I unplug the drain plug to try to get rid of sediment? I see you took a power washer to it.I might be able to rig a small hose into it. It's been stored with antifreeze over the winter (hopefully!).

Since you suspected some manifold issues, take a look at the manifold internals from the exhaust port side and also the exhaust ports on the cylinder head. If you see some rust, then I'd run a leak test on he cylinders.

You won't be able to flush much from the engine block thru the drain plugs - they are too small.

 

[wingless]

Re: Should I replace These Risers?

The engine shown does not have risers, just the manifold and the elbow.

The elbow looks fine, the manifold does not.

The issue is cold water ingress into the exhaust port, hitting the hot exhaust valve, making it brittle. When the valve fails in a running engine then the damage is severe.

 

[pyrotek]

Re: Should I replace These Risers?

Finally got the manifolds out. 16 bolts total: 11 came out normally. 3 came out with a bolt extractor. 2 needed to be drilled out. About two hours of drilling per bolt. Really should have pulled engine instead. Destroyed all my bits. Don't have a dremel and couldn't get a right angle grinder in there.

One exhaust port had a tiny bit of rust inside. Some exhaust ports were dry, other were wet with a black grease/oil

Questions:
- How did this rust occur? Now that I realize there is no water jackets between block and exhaust manifold, why is the head in such bad shape? It doesn't appear there was a leak from manifold-riser gasket.
- Should I attempt to replace the 2 or 3 rusted bolts on the head? If I leave them, they will just get worse.
- Do you recommend taking a wire brush to try to clean up the head/block and then re-prime and paint with Rustoleum spray cans?
- Having trouble finding what bolts those rusted ones are. Engine S/N: 0K035983
- Do you think it's possible these are the original manifolds? Boat is '97 with ~500 hours.

Thanks!

 

[Don S]

Re: Should I replace These Risers?

You may have had nothing worse than a leaky manifold to riser gasket. You show no pictures of the gasket surface, only pictures of the riser with part of the gasket still stuck to it. An overheat could cause the gasket to fail, but it doesn't take new manifolds and risers to cure the problem.

 

[pyrotek]

Re: Should I replace These Risers?

Bottoms of manifolds are completly corroded and need to be replaced. Unscrewing the T fitting completely crumbled the bottom.

 

[wingless]

Re: Should I replace These Risers?

Many of the nuts and bolts in my engine room have been replaced by ultra corrosion-resistant coated high-strength steel - Grade 8 hardware from McMaster-Carr, including these head-to-exhaust manifold bolts. The only ones I couldn't swap were the ones that also hold a small heat shield, so I keep those painted and lubed.

The coating on these bolts keeps them looking like new for a very long time.

 

[wingless]

Re: Should I replace These Risers?

It wouldn't hurt (except your wallet) to also swap the valves.

Chances are that cold sea water has hit the hot exhaust valves, making them brittle and prone to failure.

 

[Mischief Managed]

Re: Should I replace These Risers?

Questions:
- How did this rust occur? Now that I realize there is no water jackets between block and exhaust manifold, why is the head in such bad shape? It doesn't appear there was a leak from manifold-riser gasket.
- Should I attempt to replace the 2 or 3 rusted bolts on the head? If I leave them, they will just get worse.
- Do you recommend taking a wire brush to try to clean up the head/block and then re-prime and paint with Rustoleum spray cans?
- Having trouble finding what bolts those rusted ones are. Engine S/N: 0K035983
- Do you think it's possible these are the original manifolds? Boat is '97 with ~500 hours.

Thanks!

The leak may have been from the plastic plugs in the manifolds. You can see a lot of rust around one of them.