How to know when manifolds and risers are beginning to fail

[Jmac572]

I have been trying to search for a better answer on this.... My boat has 2004 twin 8.1s Mercury Horizons with about 900 hours on them. I have been trying to find a mechanic to come to the boat for some miscellaneous/maintenance work but one after the other keeps blowing me off, I finally found one to show up and he is telling me I need to do manifolds and risers because "he can see water staining at the manifold/riser joint, if it's leaking on the outside, it's leaking on the inside". I tried to tell him they are dry joint manifolds but he wasn't really getting it, meaning with dry joint manifolds there is no gasket to leak so there is nothing to make water stains at the manifold/riser joint.

I purchased the boat last fall and found some paperwork indicating the manifolds and risers were possibly replaced 3 years ago, but can't confirm. They appear to be in new-ish condition externally/visually.

How is one supposed to inspect these components or test them for remaining life? Is manifold temperature a good indicator? I don't want to drop $5500 plus $1500 in labor for a job that I can hold off 3-4 more years.

(For reference, here are photos of the engines, I know they don't clearly show the manifolds but they are the only photos I have access to now)

 

[superwa]

You can remove them and inspect, or check their temperature with a laser gun every couple of runs and see if it’s rising. Mine need replacing after 4-5 years in salt water. A little something to think about risk:
4 years bring failure rate to 25%. 45% at 5 years. At 3 years is 0.5%.

 

[Jmac572]

You can remove them and inspect, or check their temperature with a laser gun every couple of runs and see if it’s rising. Mine need replacing after 4-5 years in salt water. A little something to think about risk:
4 years bring failure rate to 25%. 45% at 5 years. At 3 years is 0.5%.

I'm surprised they only last 4-5 years! You would figure with a dry joint setup that water literally has to corrode 1" of cast iron to make its way and leak into the exhaust stream risking backflow into the cylinders.

 

[superwa]

I removed mine after 5 years once and they were toast. Some can last longer, but to me it’s much cheaper than repairing the engines, so I’m sticking to 4 years just in case.

 

[Korkie]

Changed ours @ 950 hrs. On inspection we were one cruise away from disaster. Indications were slowly creeping up raw water pressure, increased temp and most importantly it was taking longer and longer to recover when coming off plain. Temps would spike up and stay up before they would eventually cool down. In August when water 82 - 84 degrees would have to idle up port engine (this one was the worst) to get enough flow to not overheat. Had already changed impellors at beginning of season and had flushed with barnacle buster the oil and PS coolers. Risers were fine (SS), but manifolds were so bad could collapse inside walls with the push of a screwdriver. If your running warm and taking longer to cool down after a cruise along with (or not) higher raw water PSI, pull one off and take a look. The alternative result is not good.

 

[boatrboy]

Changed ours @ 950 hrs. On inspection we were one cruise away from disaster. Indications were slowly creeping up raw water pressure, increased temp and most importantly it was taking longer and longer to recover when coming off plain. Temps would spike up and stay up before they would eventually cool down. In August when water 82 - 84 degrees would have to idle up port engine (this one was the worst) to get enough flow to not overheat. Had already changed impellors at beginning of season and had flushed with barnacle buster the oil and PS coolers. Risers were fine (SS), but manifolds were so bad could collapse inside walls with the push of a screwdriver. If your running warm and taking longer to cool down after a cruise along with (or not) higher raw water PSI, pull one off and take a look. The alternative result is not good.

I’m curious - were they the original? If not how many years did you get out of them? Alway in salt water?

 

[Korkie]

I was told by the Mercury parts guy and the Merc service tech that helped me install them (on the side) that they were indeed the original manifolds. The parts guy said he could tell by something (I don't remember) that was only on the original manifolds. I bought the boat in 2016. It lived the first 10 years of its life in the Chesapeake bay Bridge / Kent Island area. I have kept it on a lift since we bought it. Always been in salt and flushed after every weekend of use.

 

[mrsrobinson]

@Jmac572 I agree with everyone's comments here. This is not a service you want to try to push out or save money on. Trust me, I was the happy buyer of 2 boats where they failed and the seller had to replace the engines; I got the new engines.

If you are seeing staining at a minimum, you have a leak "somewhere", pull and inspect. In my opinion if you are going to go thru the pain/trouble to pull them go ahead and replace them at the same time.

 

[Jmac572]

@Jmac572 I agree with everyone's comments here. This is not a service you want to try to push out or save money on. Trust me, I was the happy buyer of 2 boats where they failed and the seller had to replace the engines; I got the new engines.

If you are seeing staining at a minimum, you have a leak "somewhere", pull and inspect. In my opinion if you are going to go thru the pain/trouble to pull them go ahead and replace them at the same time.

Thank you for all of your input... Not going to chance it. With how short the boating season is in Massachusetts I want to set myself up for as much of a trouble-free summer as possible.

 

[MaSnaka]

My mechanic who just replaced mine said if you see saltwater crust at the joint it is also on the inside and time to change.

 

[Jmac572]

I had another mechanic borescope the manifolds and confirmed that it was time to change them out... I got the manifold kit and new elbow/risers on PartsVu for $5400 shipped to my house, expensive but they are by far the cheapest. Also doing new serpentine belts, impellers, spark plugs, MSD wires from hardin-marine, thermostats, and all new hoses with new clamps... the "deferred" maintenance by the prior owner cost me about $10k.... The boat is getting new SeaDek and a full wet sand/polish of the hull/topsides/cockpit with new boot stripes. Serious investment this spring but should look and run like a new boat.

 

[OllieC]

I had another mechanic borescope the manifolds and confirmed that it was time to change them out... I got the manifold kit and new elbow/risers on PartsVu for $5400 shipped to my house, expensive but they are by far the cheapest. Also doing new serpentine belts, impellers, spark plugs, MSD wires from hardin-marine, thermostats, and all new hoses with new clamps... the "deferred" maintenance by the prior owner cost me about $10k.... The boat is getting new SeaDek and a full wet sand/polish of the hull/topsides/cockpit with new boot stripes. Serious investment this spring but should look and run like a new boat.

Careful. I went full bore last year, including replacing my ECM when I didn't have too, because a gremlin appeared (not related to the maintenance). I did so much stuff at once without pausing to test it out, when the gremlin appeared (cam sensor), I had no idea if I caused it or not.
Fun doing it yourself tho! Enjoy..