Removing wet exhaust manifold on A27

[EZC]

Just started the removal of the wet exhaust manifold due to overheating issues. I've read a few posts here and decided it's time. I loosened 15 bolts yesterday easier than I expected. There are three socket head screws on the manifold, does anyone know if they need to be removed? Are they for anodes? I started with the nuts and bolts first thinking that would give me the most trouble. Next will be the hoses, I'll hold off on the socket head screws for now maybe someone will know. Also I'll post my progress for future reference. Thanks.

[Mainer]

Since different engines have different exhaust parts, suggest you add which engine your boat has for better detailed advice.

[EZC]

Thanks, I guess that would help. It's the Nissan ld28.

[Beta Don]

There are threads here and elsewhere about overheating LD28's and the problem is frequently the exhaust riser rotting out and not the manifold itself - That's the first place I would look because due to the design of the riser, when it rots out it can dump seawater into the engines exhaust ports. Several LD28's have been replaced because engines were destroyed by bad exhaust risers. A replacement is no longer available, but some of the threads will give you sources for custom made replacements

Hope yours is a simple repair - Cross your fingers!

Don

[TorreyWP]

To remove the manifold (which is actually a water cooled intake and exhaust manifold) was our need to remove all bolts and the three nuts. With any luck the studs will stay in the head, this will aid in removal/ assembly.

The hex head “plugs” you are referencing do not need to be removed. They are plugs which were installed in the casting process. As you can imagine the inside plumbing and routing of this thing is pretty complicated.

Just curious as to your exact overheating symptoms? Slow/gradual overheat? Fast and dramatically aster start up? Getting a look at that manifold is not a bad idea, scale can build up on the coolant side causing reduced heat transfer etc. With the unit off, I would suggest bringing it to a reputable machine shop where it can be boiled/cleaned and also magnafluxed for cracks and possible issues.

Be gentle with this thing as it is a component that is NLA and specific to the marine versions of this old beast of an engine. When reassembling, get a new manifold gasket. It’s the same gasket as the auto version so use rock auto maybe or the like.

Keep us posted!

[Mark Deeser]

After market bronze heat riser.

[TorreyWP]

Mark, that is the water mixing elbow where raw water after having gone through the heat exchanger is mixed with the hot exhaust gases and then sent through the muffler and out the back of the boat.

That mounts to the top of the intake/exhaust manifold.

Those are readily available from several manufacturers for a reasonable cost. The Sierra part number is 18-1999. That can be crossed to Barr marine, Idmar etc..

I would recommend anyone running in salt water check or replace that elbow every 5 years (unless you have a copper or stainless custom set up). This is a potential source for raw water ingestion into the engine if things rot out inside.

The marinized Nissan intake/exhaust manifold that is water cooled (engine coolant) is NLA and if that’s bad for some reason, $$$$ custom will be needed.

[Mark Deeser]

Oops, thanks for the correction Capt.

[EZC]

I removed the exhaust manifold. Wasn't as bad a job as I thought it was going to be. The overheating issue I was having was not going away after I tried many fixes, replacing raw water pump(it was in bad shape), boiling the heat exchanger, replacing thermostat, replacing coolant. This was over 6 months. It finally started to get bubbles and gasses in the coolant, I did a CO test and it was negative. About a week later started to see oily residue in the coolant. I do have a s/s riser, took it off and it appeared to look ok but at that point I was thinking head gasket or the wet exhaust manifold. So thats why I removed the manifold. These jobs can be a can of worms so the replies are really appreciated. Really hoping it's the head gasket, sounds like replacing the wet exhaust manifold isn't an option. Thanks for the heads-up on the gasket being the same as the auto, I was wondering about that. Will be taking the manifold to the shop for examination. More to follow...

[EZC]

So the head gasket has been replaced and the engine is running at the proper temperature. I had the head resurfaced and the machine shop did a good job of cleaning up carbon deposits on the valves. Found the head gasket on eBay that was a two notch gasket like the one that had been on it. It came from United Arab Emirates, which was quite a bit cheaper than the one I found in the U.S. Replaced the head bolts that were on the outside of the valve cover(rust). The wet exhaust manifold gasket also came from over seas( Britain).I did have to add a small piece of gasket material to seal a coolant port that the regular auto gasket didn't cover. I had help from a very good mechanic who use to work for nissan and was familiar with the ld28. The most intimidating part of the job for me was the overhead cam. He put a wood shim to hold the chain in place and then marked the links and sprocket so that it would be put back to the exact cog where they had been. Very important so that the timing is right. Also if the chain were to drop off the shim then the front of the engine would have to be pulled apart to put the chain back on correctly. He adjusted the valves although two could not be set to the exact setting due to wear. He said it would be ok just not perfect. I also had the injectors cleaned up and spray pattern adjusted. It starts and runs better than it did before so that was a relief. Finding parts is definitely an issue with this engine. Several websites showed that they had parts but when I went to order they weren't available. Also some websites would only work with you if you had a vin number.

[TorreyWP]

This sounds like a true success story!

Nice to know there are mechanics out there who know this engine and how to handle overhead chain driven cam shaft like this. Its certainly not rocket science but it is true that in head removal if that cain falls down, your screwed and complete engine disassembly is required.

Do you know if the chain guides were replaced? Not a big deal if not, just curious.

If you took any pictures of this process, Im sure the group would love to see them.

Glad to hear your engine is running better, its a good fit for these boats!

[EZC]

Torrey, did not replace chain guides. Definitely feel fortunate to have found the mechanic to get the job done.

[JFOkie]

EZC, I have spent a number of hours and a lot of cuss words trying to figure out my overheating problems with my Nissan LD28. I've removed, cleaned and replaced my heat exchanger 3 times, installed a new water pump and still have overheating issues. I'm ready to put a ballpeen hammer to my head and start banging away.

I'm no mechanic. I've built a few wooden boats and restored fiberglass and wooden boats, but I'm a nervous wreck just thinking about doing what you've done. I'm having trouble finding new O rings for the heat exchanger and I'm thinking about getting a larger ballpeen hammer to hit my head with.

I love the Nissan LD28, never had any issues....except for this overheating which started last summer (2018) and I'm still dealing with it. I can't seem to find anyone who can work on the engine or knows anything about the LD28. I can't even find a part number for the O ring and I have all the engine manuals.

So my boat sits there as I try to come up with Plan Q (already tried plans a - p).

John
M/V Nirvana (a motor vessel that doesn't motor)

[EZC]

John, sorry I've had a busy summer and haven't been on here. Any luck with the overheating problems? How is the wet exhaust manifold? My manifold turned out to be ok I've heard sometimes at the exhaust riser/mixer it can get clogged and cause overheating issues. My exhaust riser had previously been replaced with the stainless steel riser so it was in good shape. Actually I'm going to make a post about some ld 28 parts that I'm letting go for cheap. I'm in the middle of a repower so their either going to be thrown away or hopefully I can find a home for them. I'll post a list.