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[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".

 

[OVERBORED]

Thanks for taking the time to explain. Any shamrocks convert to diesel?

 

[Leprechaun]

My era of manufacture was available with a small-ish Perkins diesel. I've never seen or even heard of one actually being delivered. There have been a few gas to diesel conversions to Cummins 210hp diesels.

I can't see that sort of swap for reasons of cost, maintenance and the fact that such an engine will put the deck scuppers at or below waterline level. Not to mention a 26-ft boat 8-ft beam boat with a transplanted diesel will shake and vibrate excessively. Just not enough boat to absorb that much engine's drama.

Now if you just happen to have a Cummins out of a Ram pickup laying around and know how to (and can afford) to add marinization, want to replace the BW 71C with a 72C or other beefy transmission, along with a different length and diameter driveshaft and a $1500 prop, reinforce the stringers and completely redo the engine-mounting pads, have no problem modifying the cutlass bearing size in the glass/silica sand poured keel, don't mind the deck not being bailable because the scupper plugs always have to be used (except maybe underway), and KNOW that you will never see the cost come back to you should you ever sell it - well, maybe then such a swap would be for you!

Yeah, nah, from my point of view boat "hotrodding" to that extent should stay a mental exercise, not a reality. Some things should stay hypothetical. Much less drama and acceptance of eventual personal failure that way. Keep the gas, go fishing, and if you want a diesel boat, save up and buy one designed that way from the beginning . Far more peace of mind if it remains a daydream.

30 years I've owned my boat. Never once has a diesel engine made it into the top 10 (or 20) of my "upgrade wants."

 

[OVERBORED]

My era of manufacture was available with a small-ish Perkins diesel. I've never seen or even heard of one actually being delivered. There have been a few gas to diesel conversions to Cummins 210hp diesels.

I can't see that sort of swap for reasons of cost, maintenance and the fact that such an engine will put the deck scuppers at or below waterline level. Not to mention a 26-ft boat 8-ft beam boat with a transplanted diesel will shake and vibrate excessively. Just not enough boat to absorb that much engine's drama.

Now if you just happen to have a Cummins out of a Ram pickup laying around and know how to (and can afford) to add marinization, want to replace the BW 71C with a 72C or other beefy transmission, along with a different length and diameter driveshaft and a $1500 prop, reinforce the stringers and completely redo the engine-mounting pads, have no problem modifying the cutlass bearing size in the glass/silica sand poured keel, don't mind the deck not being bailable because the scupper plugs always have to be used (except maybe underway), and KNOW that you will never see the cost come back to you should you ever sell it - well, maybe then such a swap would be for you!

Yeah, nah, from my point of view boat "hotrodding" to that extent should stay a mental exercise, not a reality. Some things should stay hypothetical. Much less drama and acceptance of eventual personal failure that way. Keep the gas, go fishing, and if you want a diesel boat, save up and buy one designed that way from the beginning . Far more peace of mind if it remains a daydream.

30 years I've owned my boat. Never once has a diesel engine made it into the top 10 (or 20) of my "upgrade wants."

Thanks for the explanation. I know a friend owned a similar sized Sisu with a small John Deere that ran like a top. Different boat. Different specs.......Best of luck this season.

 

[longcast]

I had a guy in the marina that converted his Shamrock to a diesel. He worked for the marina and did all his own work. Not sure what marina he is at now.

I see him fishing once in a while

 

[MakoMatt]

There was a guy in the slip next to me for many years in the Tuna Club. I think he had 26’ Shamrock, with a small Perkins. I can’t remember the name of the boat, his name was Ron something……. He loved the boat and had canyon fished it back in the day.

 

[MakoMatt]

There was a guy in the slip next to me for many years in the Tuna Club. I think he had 26’ Shamrock, with a small Perkins. I can’t remember the name of the boat, his name was Ron something……. He loved the boat and had canyon fished it back in the day.

Lep, do you remember this boat, FISH HAWK II? This is the boat I was referring to, his name was Ron, he had a slip next to mine. Don’t know if he was a member of your Shamrock Club. He passed away some years ago.

 

[Leprechaun]

No Matt, I don't recall that boat. But my memory is not what it used to be, so there's that . . .

Looks like he kept a nice clean boat.

 

[MakoMatt]

No Matt, I don't recall that boat. But my memory is not what it used to be, so there's that . . .

Looks like he kept a nice clean boat.

Pete, welcome to my world on the memory thing.
He did take good care of that boat. He also loved Fluke fishing, and was very good at it.