www.iFourWinns.com

Marine mechanic (very well respected) talked me into a new long block after repairs to my stern drive separating from hull. "As long as we have engine out -- there are so many problems let's make it all good." We agreed on a set price, so I am good with the project -- but it is going sideways. New engine is in. All hooked up. But it sounds like an unmuffled dragster at the Saturday night races. I included link -- the sound in person is a lot more pronounced. Before the exchange the engine would purr inside the engine bay. Now it turns heads, even covered by the back seat cushion. On sea trial it came out of the hole pretty well, but the longer we drove the less power it had until it could barely get out of the hole and max RPM was about 3300. We went back to the dock where the mechanic is a bit mystified.

https://youtube.com/shorts/MA7UEtxjCv4?feature=share

Engine starts fine
Engine idles fine
Temp is a steady 170
Oil pressure perfect
Alternator charging perfectly
No water leak from engine
No liquids leaking, period

There is some smell of exhaust, more annoying than overwhelming.

Obviously, the mechanic is frustrated. He is now upside down on this project, and I will be, too.

He suspects the gasket under the plenum might be bad, hence the loud exhaust noise.

Anyone else want to take a stab in the dark over what comes next? It's a great looking boat, excellent shape for its years (1996) and I am this close to selling it was a mechanic's special, if people even buy those anymore.

Thanks, as always.

Mark

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Four Winns 1996 Sundowner 205
5.0fi/SX engine (Volvo Penta)

I can now add that the intake gasket replacement restored the power. But there remains an exhaust leak. Loud as @#$%. New target: Exhaust manifold gasket (although no water is seen anywhere)

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Four Winns 1996 Sundowner 205
5.0fi/SX engine (Volvo Penta)

I don't have any experience working with I/O systems, but a lot of experience working on cars/trucks.
That does sound very loud, especially if it's not a "Captain's Call" exhaust type setup. About the only thing I can suggest is getting in/around the engine to try and determine where the sound is coming from, or at least is the loudest. Check every connection, mounting flange, etc. Something isn't seated right or connected correctly.

Best wishes for a quick and easy fix. Sorry I can't help out more.

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1999 180 Horizon OB Fisherman Pkg
2013 Grand Cherokee 4x4 w/ 5.7 Hemi
San Antonio, TX

that should not be that hard to track down, as loud as it is. I'd be looking at the exhaust manifold to cyl head joint for carbon, you probably could feel the exhaust coming out. How is the exhaust temperature? Are you getting good flow through the manifolds & elbows? Were they checked before installing on the new or reman engine? I've changed the exhaust 3 times on my engine (par for the course over 20 years in salt water) and never had an exhaust leak. First, try checking the torque on the exhaust manifold bolts, should be around 25 ft lbs. Second, check the rubber boots for any sign of water leakage, sometimes after the install the clamps need to be retightened.
Did the mechanic use new manifold to cyl head gaskets?

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

I get new info pieces at a time. He’s a confident mechanic and I’ve known him for years — he expects things to work. But this is a challenge I suspect that is partly his own making. The gasket under the plenum was easy to fix. He now suspects exhaust manifold because he changed the configuration to raise them ever so slightly hto make them more accessible in the future. He was proud of his idea (true replacement parts no longer available - the curse of an old boat/engine) and is coming to grips with the idea that there is something really amiss with that. It’s the obvious suspect. The whole Exhaust system will come off and go back on. He is ups$de-down on this project because he talked me into it at a base price as a favor to me. I’m upside down any way you look at it.

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Four Winns 1996 Sundowner 205
5.0fi/SX engine (Volvo Penta)

That's a Ford engine and while the engines themselves were good, they stopped using them a long time ago so parts availability is a bigger problem than what you'd have with a Chevrolet engine. OMC and Volvo used them up to the late '90s. Mercruiser has not used them since the '70s. I'm thinking what he did or tried to do was to make it easier to get at the spark plugs, this is a problem with certain marine manifold designs, due to the water passages needed to keep them cool. Some people wound up grinding down a spark plug socket to get at the plugs more easily.
On my old '88 Chevy 4.3 I never had trouble getting at the plugs, either with the original one piece OMC V6 manifolds or the Barr aftermarket 2 piece manifold/elbows I replaced them with.

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

That is exactly what he did. And he used gasket on the riser that he was not sure of. They ended up just blowing up under the huge pressure. (picture of gasket) It broke in two just picking it up. https://www.dropbox.com/s/tcbj33mcbr5n8bv/gasket.jpg?dl=0

So he's mad at himself for not going with the prescribed gasket and has to pull off the exhaust manifold and scrape it down to smooth. It's a long process. Also threw in shot of the old manifold https://www.dropbox.com/s/457eq76wuxd2wwe/manifold.jpg?dl=0

...and the old block https://www.dropbox.com/s/5ws5roryegazao1/block.jpg?dl=0

...which, if you look in the corners, showed a lot of rust. Seawater. I flush it every trip, even use Salt-Away -- but if you miss one little spot....well, rust never sleeps.

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Four Winns 1996 Sundowner 205
5.0fi/SX engine (Volvo Penta)

We have not come far. The mechanic is now taking this personally. He is the one who talked me into the new long block and so he feels a sense of ownership. After the "loud engine" incident (where you could smell exhaust from the engine bay) he replaced the manifolds and plenum gaskets. He dropped the prop in the water and fired it up. Normally you'd just get a nice purr from the engine while the exhaust is buried in water, but we got this again...

https://youtube.com/shorts/P_ZZKHr-kZs?feature=share

You can hear him talking to me just behind the engine noise, which is still loud UNDER the seat covers.

He's as frustrated as me - it's been a thing since December. He thinks the only thing left to do is pull the engine and inspect the connection where the exhaust Y bolts to the transom shield.

One more fact: The engine or connections are NOT leaking water. It's just loud as _____.

Any hail mary's out there?

Mark

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Four Winns 1996 Sundowner 205
5.0fi/SX engine (Volvo Penta)

I can reply TO MY OWN POST with the fix! The mechanic was awake all night wondering what was causing it and at 3:30am he had an epiphany. The new long block was built for a ford truck that is EPA compliant. It has EGR ports in the back of the heads. The old engine did not have those. He found them and plugged them. The video below is the holy grail of inspirations:

https://youtu.be/hSxpaxbGG_E

Now it just needs to go back in. And I will have probably 2 weeks of boating left on the calendar. Ha! I'll post final report mid-September.

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Four Winns 1996 Sundowner 205
5.0fi/SX engine (Volvo Penta)

Well that’s great! Great mechanic too that he kept at it till he found the solution. Enjoy the rest of the season!
These things happen with old stuff where you have to improvise because you can’t just go out & buy new parts. I have a lot of good used parts for my old 1988 Cobra system, the boat still runs great despite being 35 years old!

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II