Post your 2019-2025 Fluke Pix & Trip Reports Here!

[Leprechaun]

Well, its that time of the year yet again. Time to get going on needed repairs, upgrades, maintenance and Spring Prep.

So, last Fall I wrote that I thought I had an exhaust manifold leak - turns out I had two, one on each side. Geez, I can't believe that it was such a minor sound, given what I found today.

Got busy pulling the old, used-up exhaust system off the block. And it turns out my diagnosis was correct.

Port side #8 exhaust port - badly burned/corroded from whatever nasty stuff the engine generates. This is the tapping I heard at idle:

But look at Starboard side #4, even worse! And yet I never heard a thing on that side of the motor.

Of course being a gas inboard with the exhaust manifold bolts below deck level, this knowledge does not come without some expense, and I don't just mean monetary-wise, thought that's also pretty nasty.

Just the price that must be paid to keep her in shape to find those ocean fluke this coming season. On the old Shamrock Owner's board we used to say "any job worth doing is worth leaving a little bit of yourself in the bilge."

Truer words were never spoken.

 

[Snapprhead27]

Geez Pete! I give you lots of credit

 

[BoatGuy]

Wow....That is corroded! The joys of salt water!

 

[OVERBORED]

The good news is you know how to fix it yourself.
The bad news is you know how to fix it yourself!

Good luck with the repairs.

BTW, How many hours did you get out of the old manifolds?

 

[Leprechaun]

BTW, How many hours did you get out of the old manifolds?

Hah, good question! 10 minutes for each of the risers. One hour on the port side manifold. Not bad, considering the last four bolts have to be done by feel alone. The starboard side manifold, one hour to get out 7 of the eight bolts. The last, rear-most bolt, another hour plus.

Just can no longer contort my body enough to wedge my average-length arm back there from the front of the engine, as getting to it from the side is impossible - for me. Another example of getting too old for this, um, "stuff." I cannot image doing this for a living. Mad respect for marine mechanics everywhere - makes automotive repair look like a walk in the park.

One helpful tip is to NOT use the factory BS iron bolts that are OEM. They corrode badly, rust-freeze in the heads despite using liberal quantities of Never-Seize, making a tough job even tougher. Anyone in the know uses stainless steel "cap screws," with a good-quality 3/8" hex-drive socket - mine is Snap-on, of course! Still not a job I will ever look forward to, but these make it just a wee bit "better."

Also, always use fresh grade-8 lock washers every time the manifolds get changed - which according to universal gas inboard ritual thinking is at 6-year intervals.

One other tip - be a bit of a masochist. It kinda helps.

 

[OVERBORED]

Well done!

 

[Leprechaun]

BTW, How many hours did you get out of the old manifolds?

Sorry, I misread your question before having my morning high-test. Yeah, well irrespective of hours run, the risers need changing out every three seasons (easy job), and both the risers and manifolds have to go at six seasons. Sitting or running the internal rust never sleeps, so the safe bet is at those intervals.

This is mandatory with a "half-closed" FW cooling system, because the cast iron mani/risers route the SW out through the exhaust pipes. This is different than a "closed" system, which includes the manifolds in the FW side of the cooling system. Most gas inboards are like mine, half-closed system.

Examples of the "full" system would be the Mercruiser Horizon series and I think some of the higher-end Crusaders. The down side of this cooling method is that the oversized engine heat exchanger must be watched like a hawk, and fully serviced or replaced when running temps move upward even a tiny bit - assuming that the RW pump has been regularly serviced as well. The H/Ex in these Full systems carries a very heavy load, considering they have to cool the engine AND the manifolds.

I think my half-system is better, but that's just my way of thinking. I'll trade-off more grunt work to eliminate possibly cooking the engine, should the H/EX clog or perforate 20 miles from the dock.

There do exist certain types of Stainless Steel riser/manifold setups - usually one piece. Locally there is a custom exhaust fabricator in Farmingdale that can build a set of SS exhausts. My friend had a pair on his Shammie, sister to mine w/the same PCM/Ford engine as mine. For some reason those SS manifolds would blow out their exhaust gasket every couple of seasons. I think it was a thermal expansion mis-match between the cast iron engine block and the SS exhaust, but we never did get to the bottom of that particular issue. He passed away at the age of 53 from a massive heart attack. Another of my closest friends gone forever.

Anyway, that was the $5 course in gas inboard marine exhausts. Congrads, you got an "A".