Replacing exhaust manifolds, risers

[rwc]

I recently bought a 2004 2500 SE. The boat has closed cooling and lives permanently in salt water (and has always done so).

During the inspection, the mechanic told me to go back and check the maintenance records to see if the exhaust manifolds, risers, and elbows had been replaced. He said they should be done every ten years at a maximum to avoid hydrolocking a cylinder and destroying the engine. They had not been done based on records, so I negotiated the price down for the maintenance. Is this reasonable, in line with what you guys do?

Mechanic is now saying that I should replace the manifolds and elbows, but might be able to keep the risers if they are not too badly corroded. It seems to me if the whole thing is pulled apart, I should just replace those too to avoid needing to worry about it for another ten years. Thoughts?

Also, I didn't see any record of the bellows being replaced, so I asked the mechanic about that. He said as long as the drive wasn't being lifted often (boat hasn't been trailered) they can last a very long time. I want to replace it, but he seemed to be trying to talk me out of it if the rubber looks ok. Maybe he just doesn't want to do the job?! Based on what I've read here and the fact that I have no idea when it was last done, I think I should tell him to go ahead and change it. Am I missing something?

[Phillbo]

Do it all so you have a baseline of when everything was replaced going forward.

I own the exact same boat (year and model). You'll be happy with it I'm sure.

[rwc]

Thanks Phillbo! I was thinking the same thing with establishing a baseline. If nothing else, I'll sleep better.

Mechanic is a really nice guy, but keeps talking about doing what my cashflow will allow - I feel like telling him to let me worry about that! Better for my cashflow if I maintain rather than repair.

Since you have the same boat and while I've got you on the line, are there any other maintenance type things I should do at the same time? I'm new to boating and have made a number of silly mistakes already, so would appreciate the help. (This weekend, I couldn't keep the engine running and was losing my cool, until my slip neighbour helpfully pointed out that I might not have the Run switch turned on - I didn't...)

I'm also considering changing the drive leg oil, painting the drive leg, replacing all zincs, greasing prop splines, greasing U-joint, flushing cooling system on both sides, and replacing the thermostat (just cause the coolant is out).

Should I go for oil and fuel filter changes too? Anything else?

[Phillbo]

When was the last time all the fluids were changed? It should be done annually. How many hours on the engine and what engine package do you have?

Hey, your not a true boater if you have not tried to start it with the kill switch turned off. I know people that have taken their boats into the shop only to have the mechanic find the switch off

[mmwjr]

You said the boat has closed cooling is it a half or full system? Half only does the engine and full also does the exhaust manifolds. If full only replace risers and elbows if half also replace the manifolds.

[mmwjr]

What is the condition of the bellows? If ten plus years old they should be replaced.

[rwc]

If it hadn't been for my neighbour, that very well could have been me! Didn't help that my MIL was onboard giving me that you-don't-really-know-what-you-are-doing look.

The previous owner seemed to conduct quite regular maintenance, but only had records to 2014. I'm pretty sure the fluids have been changed since then since they look quite good, but no way to know for sure. The boat was in winterized condition when I bought it and hadn't seen that much recent use, but I know he had it out a few times in the last 6 months. I think I'll just get them changed.

Engine is Mercruiser MCM 5.7L. Drive is a Bravo 3. It has 766 hours on it. Compression is pretty good, with one cylinder at around questionable range relative to highest, but not outside. Idle is good. Temp stays at exactly 175, though it alarmed at 185 second time out due to low coolant level. Topped it up and it has been fine since. WOT is 4000, which I know is low, but I don't know how big a deal that is. Doesn't seem that much low and it planes just fine at 3200, which is where I tend to stay.

[rwc]

Originally Posted by mmwjr

You said the boat has closed cooling is it a half or full system? Half only does the engine and full also does the exhaust manifolds. If full only replace risers and elbows if half also replace the manifolds.

I think it must be half. Pretty sure there is raw water through the manifolds. I will be sure to check though. The manifolds look like the most expensive piece!

[rwc]

Originally Posted by mmwjr

What is the condition of the bellows? If ten plus years old they should be replaced.

I don't know yet. Without info to the contrary, I suspect they are as old as the boat. I figured since the mechanic is pulling off the leg to paint it anyway, I might as well get it swapped, but he surprised me by saying it might not need to be done. He said if the drive isn't raised regularly, they can last a very long time.

My concern is that they "can" last, not that they "will" last.

[mmwjr]

Originally Posted by rwc

I think it must be half. Pretty sure there is raw water through the manifolds. I will be sure to check though. The manifolds look like the most expensive piece!

Being 2004 they may be what is know as dry joint, which has external water tubes between the manifold and riser and elbow where the old style wet joint has the water passages cast into the pieces.

If the manifolds are closed cooled they will have two hoses one one bottom and one on the top.

[mmwjr]

Originally Posted by rwc

I don't know yet. Without info to the contrary, I suspect they are as old as the boat. I figured since the mechanic is pulling off the leg to paint it anyway, I might as well get it swapped, but he surprised me by saying it might not need to be done. He said if the drive isn't raised regularly, they can last a very long time.

My concern is that they "can" last, not that they "will" last.

If they are that old the rubber will become hard and crack easier. With the drive raised look between the folds for cracking in the rubber. When they fail water will leak into the boat and can sink it if unattended. A leaky driveshaft bellows will also ruin the gimbal bearing.

[rwc]

Originally Posted by mmwjr

If they are that old the rubber will become hard and crack easier. With the drive raised look between the folds for cracking in the rubber. When they fail water will leak into the boat and can sink it if unattended. A leaky driveshaft bellows will also ruin the gimbal bearing.

Thanks Mike. I will check it out when the boat is next lifted. There is water in the bilge. I pumped it out and now I think there is a little more than the remaining bit I didn't pump. Not sure if this is salt or rain water, but I suppose it could be a slow leaking bellows. How quickly does it ruin the gimbal and is a very slow leak enough to do it?

[mmwjr]

It will ruin the bearing quickly but it may not show signs right away. Cheap enough to replace while doing the bellows. I would also replace the lower shift cable while you are there. They actually sell the bellows, bearing and cable as a kit.

[mmwjr]

Forgot to mention to check for play in the swivel shaft which is the steering pin at the top of the transom assembly. When the boat is out try moving it side to side by pushing on the drive. Common issue and compounded by not verifying the torque on the topic u bolt yearly.

[mmwjr]

Also forgot to say replace the water hose on the transom assembly while doing the bellows as on Bravos this us know to clog due to the use of an insert to lock it in place. The hose also comes with the kit.

[rwc]

Hi Mike.

Checked out the exhaust system and suspect it is dry joint like you described, but entirely sure. I attached some pictures. the first shows two hoses going to the riser and elbow, which is I think what you were describing. The second shows that there is surface corrosion on the manifold. If it is dry joint can I just clean and paint the manifold or is it reason enough to replace the whole thing?

The water hose you mention in your last post, is that the raw water uptake for the cooling? I have an aftermarket thru hull uptake and the drive uptake has been capped off. If that's what you meant, presume that means I dont have to worry about it?

[rwc]

sorry about pics being upside down. oops.

[mmwjr]

Originally Posted by rwc

sorry about pics being upside down. oops.

I hope the boat is right side up.

[mmwjr]

Originally Posted by rwc

Hi Mike.

Checked out the exhaust system and suspect it is dry joint like you described, but entirely sure. I attached some pictures. the first shows two hoses going to the riser and elbow, which is I think what you were describing. The second shows that there is surface corrosion on the manifold. If it is dry joint can I just clean and paint the manifold or is it reason enough to replace the whole thing?

The water hose you mention in your last post, is that the raw water uptake for the cooling? I have an aftermarket thru hull uptake and the drive uptake has been capped off. If that's what you meant, presume that means I dont have to worry about it?

Yep dry joint.

It appears that the manifolds are closed cooled but I cannot be 100% sure. The lower hose is coming from the heat exchanger but not sure if its on the closed side or raw water side. Guess you can loosen the hose to see what comes out.

That rust is pretty bad and suggest a leak. You will need to take it apart to inspect to see if it can be cleaned up or not.

Ok and thru hull seacock was added and the transom raw water hose has been blocked, no issues.

[Phillbo]

For a second there I thought he was from Australia, not BC

I had to turn my monitor up side down.