Should I replace These Risers?

[tpenfield]

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!

Just notice the pictures of the cylinder heads . . . in answer to your question . . . On the 454 engine the exhaust gasket traps water and hold it against the cylinder head so that everything can rust. I'm not sure what you can do about it, except keep after it.

Yours look good compared to what my engine looked like when I tore it apart last fall. The head bolts were a socket size smaller from the rust flaking them away. I barely got them off without snapping the head of the bolts.

Anyway, your cylinder heads look OK and are quite fixable with a wire brush and some paint as you mentioned.

BTW - you are lucky, I had to pull my engine in order to get the manifolds off. The bolts were pretty trashed and I had to mill the heads of 3 bolts off. The others came with a bit of work.

 

[pyrotek]

Re: Should I replace These Risers?

Most people told me I was nuts for trying to take those head bolts off. So I agreed and I am not touching them. I guess if and when they actually need to come out, the engine will be out and it will be simple to grind them off, worst case.

The surface of the exhaust is not perfect, but I'm hoping it will not leak. I do not want to have to take all this apart again. If I was to do it again, I would have pulled the engine. Too much time lying on the ground at a terrible angle.

I wire brushed (with a drill) most of the rust. I scraped/chipped the rust off as best as I could with a flat screwdriver. Then today I primed and painted the lower engine. Hopefully this protects the engine.

I re-ordered the plastic fittings at the bottom. I noticed they also carried brass fittings. I'm wondering if those are preferred instead of the plastic?

Here's a few pics of my progress. I started taking masking tape and covering the exhaust ports, but then came up with a much better idea to cut out the shape of the new gaskets using old gasket material, and bolt it over the ports while I sprayed paint.

 

[wingless]

Re: Should I replace These Risers?

I re-ordered the plastic fittings at the bottom. I noticed they also carried brass fittings. I'm wondering if those are preferred instead of the plastic?

When I've purchased new Mercruiser exhaust manifolds they come with new brass fittings.

Your image shows a drain below the manifold, then the hose angles upwards, trapping raw water within the cast iron.

The degradation of the manifold would decrease if the raw water drained after usage, either by opening that drain or by re-routing the hose to utilize gravity.

Most people told me I was nuts for trying to take those head bolts off. So I agreed and I am not touching them. I guess if and when they actually need to come out, the engine will be out and it will be simple to grind them off, worst case.

Those head bolts have a three stage tightening sequence specified in the manual.

There is no specification for loosening / removing then replacing some head bolts.

If there is access for changing the exhaust in the boat, then removing / replacing the heads can also be done in-place.