496 exhaust manifold cleaning?

[Carverlvr2]

My 2004 366 with Volvo Penta 8.1’s has been fresh water its whole life. Worried about the cost of new risers and manifolds, I have the marina pull the riser after survey and they sent me this pic but would not elaborate on weather this was normal/acceptable buildup and certainly no offer of cleaning. Pretty sure they’d be happy to add up the $$$$ to replace though. So again I turn to the vast body of knowledge, experience, and general wisdoms this group has to offer!
1. Is this “Normal and serviceable/acceptable”?
2. If not, can/should they be cleaned?
3. If yes, how? Could a radiator shop dip the manifolds and risers? Who does this work?

[buster53]

Big question, are your engines raw or fresh water cooled? If fresh water cooled are the manifolds part of the closed cooling system? If they are, chances are real good the manifolds will never need to be replaced. Risers yes, manifolds, no.

[Carverlvr2]

As far as I know It’s only raw water cooled. I didn’t see any extra plumbing or reservoirs but have not been very deep in the engine room yet. Looked like hoses go from thru hull sea strainer strait to the engine. What should I look for?

[bud37]

QR_BBPOST As far as I know It’s only raw water cooled. I didn’t see any extra plumbing or reservoirs but have not been very deep in the engine room yet. Looked like hoses go from thru hull sea strainer strait to the engine. What should I look for?

Do you have all the risers and manifolds separated and off the engines now ?

Do your engines run cool now and are the risers cool to the touch on top with engines running, also are your exhaust hoses cool to the touch ( no hot spots ) if so all ok IMO.

Actually if it were me , that pic you showed does not look bad from what we can see....I would just flush out to make sure passages are clear and move on unless you want to have them boiled out and resurfaced at an engine shop , really all about the budget and peace of mind.

One thing for sure if they are removed and replaced you will be sure that down the road they can be relatively easy to re and re.

[Carverlvr2]

The riser was only pulled after the survey just for quick inspection. I’ve only run the boat once since buying and then it was winterizing time. Ran it over an hour and gauges showed it ran steady and cool. If I do pull them all, I’ve read it’s the port engine outside set that’s a pain to get to. Any tips?

[bud37]

QR_BBPOST Any tips?

Take it to a different mechanic and see what he/she says....... Really not enuf info for me to advise you one way or the other.

I am sure others with more experience will chime in soon.

[buster53]

QR_BBPOST As far as I know It’s only raw water cooled. I didn’t see any extra plumbing or reservoirs but have not been very deep in the engine room yet. Looked like hoses go from thru hull sea strainer strait to the engine. What should I look for?

Easiest thing to look for is a heat exchanger. It’s a cylinder sitting on top of the engine, maybe 1-1/2’ long, 4-5-6” in diameter with a couple hoses/tubes coming out of it. It acts as a radiator on a car engine, but instead of air passing thru, sea water comes in and removes the heat from the closed cooling system.

[km1125]

Post up a few pics of your engine(s) and someone here can probably give you better guidance.

Whether raw or freshwater cooled, the main cooling hose from the sea strainer would go to the raw water pump on the engine. After the raw water pump is where the differences between raw and fresh start kicking in.

[thatchh]

I agree with Bud37, It's not so much the overall engine temp at the gauge, although if it runs hot then there is definitely problem to be diagnosed. The passages and gasket faces look pretty good to me. The time to check it would have been before it was disassembled. If it's just the one, put it back and run the engines idle and hard and check with an infrared thermometer for any hotspots. The engine must be running, as the risers will heat soak once you shut it down and give you a false impression of temp.

[Carverlvr2]

It’s definitely raw water all the way through. One hose from the thru hull to the engine and then just exhaust back out. De winterizing is in the next few weeks. I have a temp gun. What temp(s) should the manifolds sit at? Also, I read the VP manual and it’s says there’s a flush port in there somewhere. Is there some device I can connect that would flush a de scaling chemical through the system?