How can I identify if manifolds/risers are leaking water into exhaust?

[fhh11]

Like many LM318 owners I want to make sure that I do not ruin my engines by allowing raw water engine cooling water from entering my engines through leaks in the exhaust manifolds or risers thereby causing rust or, worse yet, causing hydrolock. I know I should look for signs of leakage around the manifold and risers gaskets. I also know that I should look for steam in the exhaust (how to tell steam from unburned fuel?). I have my oil analyzed after every season to see if there is water in the oil. What else should I do? Should I take the risers and manifold off and have them tested by a radiator shop? Is there any safe way to test the manifolds and risers when they are mounted on the engine?

Any advice from forum members would be appreciated.

Engines: Raw water cooled counter-rotating Chrysher 1988 LM318 with center-riser manifolds;
1900 engine hours on original risers and manifolds always operated in fresh water and well cared for by all owners.
Boat: 1988 Marinette 32 fly-bridge sedan cruiser

[jralbert]

Sounds like you are doing the right thing but perhaps it's time to pull the risers/manifolds and check their condition. You indicate the hours on the engine but if the cooling system is as old as the boat, it's time to get a first hand look. Those parts corrode even in fresh water. I've seen it reported that about 10-15 yrs is the expected life. Mine held about 20 in brackish water. Folks who have pulled them advise doing so carefully - breaking a bolt is unpleasant

[Fastjeff]

IF you have log manifolds, water from leaking risers or gaskets will drown the last cylinders (# 8 and # 7). If the manifold itself is leaking, all cylinders on that side will get wet.

IF you have center dumps, water will enter all of the cylinders except # 1 and 2 (unless the manifold itself is shot).

On removing manifold bolts...DON'T twist them off! The bolt will either start to unscrew immediately, or fight you. If the latter, STOP! Using a bunch of nice, sharp drills, drill the head off the bolts, then wedge the parts off with wooden wedges. With the manifold off, you can Vise Grip the bolts out (wiggling them back and forth until the loosen up). Be careful here, for breaking off a bolt in the head requires an Easy Out (and if IT breaks off....)

Note: I'd avoid using an angle grinder to remove the heads--too much of a fire risk in the bilge.

On installing the parts...Despite what OSCO or Barr says, use a THIN coating of silicone on both sides of every gasket in the water jacket. Trust me on this! Be sure all the threads are clean (run a tap), the bolts are all new, grade 8 (six marks on the heads) and that you use a good anti-seize on the threads. Tighten them good--don't use a torque wrench, just common sense--and then retighten them after the parts are fully warmed up. I can usually add a flat or two (6 flats per bolt head).

Good luck!

Jeff

[fhh11]

Thanks Joel and Jeff! It sounds like this is a job you have faced before. The manifolds and the risers are original and are now 27 years old. The engines have never been stressed and have operated mostly under 1500 RPM on the Erie Canal for two to three months of each year. Perhaps that is why the manifolds and risers have lasted this long. Your advice Jeff on how to remove the manifolds and risers is much appreciated. Do you think I can remove the manifolds in the boat? Getting to the outboard sides of the engines with tools to remove the bolts seems really difficult if not impossible. Advice on this is really important to me as I live in Virginia 600 miles away from where the boat is located. It might be better for me to have the yard here pull the engine and put it in my truck for transport back home where I can work on it or possibly to have the yard do the work.
Your thoughts? Floyd

[jralbert]

27 years on manifolds is at or past their life span. The mode of running as you described it doesn't factor in. As for a 1200 mile round trip, that is a love of boating. Beats Jeff's Allentown PA to northern Chesapeake Bay by lots of miles. Only you can determine whether you have the skills to do the work and the value of time (and miles on your truck). And the competence of your yard. Another thought is to take some time if you have it and pull boat just prior to season's end and do the work yourself at the yard (maybe hire a yard mechanic to assist) making very certain you have all the parts on hand so you can work straight through. A day or two on each engine should do it. And, if you need company, pick up Jeff along the way north. He is getting blue about not having any engine work to do for a while.

[Fastjeff]

Sure I am!

Pulling the motors to change manifolds is a bit drastic, but I understand. No way those bolts are coming out after being in so long! You might want to try this:

1. See if the 'easy to reach' parts will come off. If so, go for the rest.

2. If the bolts aren't coming out without twisting off, you could pull the outer heads off and fix things that way--much less $$ labor than yanking the entire motors!

Good luck!

Jeff

[fhh11]

Well guys I took off inboard manifold and riser with no difficulty at all! Everthing looks OK with no signs of rusting or water leakage. I am really amazed at the apparently good condition of the manifold and risers, but then how would I know if the walls are thick or thin within? Any thoughts on how to test the manifold and riser? Should I take them to a radiator shop or simply replace them?

Later today I will remove the four spark plugs (2/4/6/8) that are now accessible and I will report on their condition.

Floyd

[fhh11]

I removed the spark plugs for cylinders 2/4/6/8. 2 and 4 show some fuel fouling. 6 and 8 look normal with light brown coloring of insulator. I will replace the plugs and check the automatic choke assembly to see if that is causing the fuel fouling. Any other suggestions?

Further inspection of the risers and manifolds suggests I should replace the risers. I will order two Barr 534005 generic risers and the Barr 534002 adapter plate/gasket kits for my port engine. I think the manifolds are OK despite their age. It will be next Spring before I can report results.

Floyd

[Fastjeff]

Hell to have to wait that long to find out...

Be sure to coat each side of each gasket with a THIN coating of silicone (despite what Barr ands OSCO say).

Jeff

[Tranquilo]

Had a nice little incident yesterday while fishing 10 miles out at sea..

I cruised out without much incident (motor runs rough because I'm sure the damn distributor is shot - another story)

When I was almost at my destination, the engine would start stalling at anything above 1800 rpm. So I decided I went far enough (I still had a bar of cell service) I anchored and let my friends go fishing while I checked the fuel filters. Changed filters and reconnected the fuel lines.

Went to start it and it wouldnt turn, just "knock". I unplugged a bunch of 12 volt stuff and checked the starter connection. Went to turn it over and it reluctantly did but as it was starting I heard a good "KNOCK". She was running ok. I still couldn't run fast but we motored back, stopped and started without much incident. Slowly, we made it back to port.

Once back, I pulled the plugs and did a compression check because I was getting steam out of the right side and feared a head gasket failure.

Plug #8 was soaking wet (right side). Was not corroded, did a compression check last week and all was good and dry.

Compression readings were:

1- 125psi
2 - 155psi (strange but verified)
3 - 115psi
4 - 120psi
5 - 120psi
6 - 125psi
7 - 125psi
8 - 125psi

Once again, I was waiting on a manifold that didn't show up on Saturday as scheduled.

Not sure what to do except change the manifold. How likely is my engine just toast?