88 300 WE exhaust system maintenance

QT1

Active Member
Oct 20, 2016
645
Belair, MD
Boat Info
1990 350 Sundancer, "Quality Time II".
Engines
454 Mercruisers, performance parts modified by PO.
The title says it all. Any suggestions? Thanks.
 
Raw or fresh water cooled? Used in fresh or salt water?
 
Fresh water cooled.
 
I'd pull an elbow or two and have a look at the condition of the passages, if good reuse, but if corroded, replace. Examine the manifolds if they are raw water cooled, if you have a full closed cooling system, then they are probably fine. Risers/elbows always have raw water going through them so pay close attention to them, especially if you are in brackish to salt water. More than a few engines have been ruined by water intrusion from bad elbows. Gaskets are cheap. Check the exhaust hoses, if brittle, replace.
 
You’ve got the 5.7’s and it sounds like you are not too sure about the age or condition of the exhaust.
Seems like the boat may be new to you.
If the whole exhaust is raw water cooled, just to be safe:
My advice would be to just get a new OEM Mercruiser E coated exhaust kit and start fresh. The 5.7’s are really common and as a result they are about the most competitively priced exhaust systems out there.
Too easy to lose a motor because of water intrusion through the exhaust.
You can usually find a sale that will get you the whole kit for about $600 a motor.
If the manifolds are cooled by anti-freeze then I would replace the Risers/Elbows (very quick and easy job on your boat) for peace of mind.
 
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You’ve got the 5.7’s and it sounds like you are not too sure about the age or condition of the exhaust.
Seems like the boat may be new to you.
If the whole exhaust is raw water cooled, just to be safe:
My advice would be to just get a new OEM Mercruiser E coated exhaust kit and start fresh. The 5.7’s are really common and as a result they are about the most competitively priced exhaust systems out there.
Too easy to lose a motor because of water intrusion through the exhaust.
You can usually find a sale that will get you the whole kit for about $600 a motor.
If the manifolds are cooled by anti-freeze then I would replace the Risers/Elbows (very quick and easy job on your boat) for peace of mind.
You must have been reading my mind: First and foremost, the risers and manifolds. It's just been disturbing that the last 2 owners, who I now know, didnt keep any maintenance records, so I have started from scratch with all maintenance procedures and dates.
 
You must have been reading my mind: First and foremost, the risers and manifolds. It's just been disturbing that the last 2 owners, who I now know, didnt keep any maintenance records, so I have started from scratch with all maintenance procedures and dates.
Don’t feel bad. In the summer of 2016 I picked up a 2005 18’ Maxum Bowrider with a 3.0 Mercruiser in it on a trailer for my kids to use. Boat ran good with normal temp so I put off doing the exhaust until the Spring of 2017. I was stupid and extremely lucky at the same time. The old exhaust was a mess when I removed it. Very stupid on my part. Lucky I didn’t ruin the motor.
In hindsight, I should have done the exhaust and the impellers in the drive as soon as We got the boat.
 
port raw water pump impeller done, starboard impeller coming up in the next few weeks. Impeller also done on Westerbeke genny.
 

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