Engine inspection tips for used 4.3L V6 or 305/350 V8 equipped mercruiser I/O setups.

havoc_squad

Senior Chief Petty Officer
Joined
Mar 5, 2011
Messages
738
I'm in the market currently for a used non-fishing layout cuddy of 21ft or smaller, which usually is hard to find in the outboard setup in the mid central US.

Possible, but hard to find. So, that means most of them are going to be in the I/O category. Do not want an OMC cobra or Volvo penta.

I've owned a 1993 mercruiser 3.0L inline 4 previously so I'm aware of many of the subtle details about I/O's.

I'm in no hurry though, so focused, detailed, and patient is the goal here.

I know used marketplace is the primary location where people try to dump I/O boats with cracked blocks.

So, mercruiser is probably what I will be up against and most likely the 4.3L V6 or 305/350 V8 of a boat year 1992 to around 2000.

In no hurry here, so I can wait things out. Focused on looking primarily after labor day.

I'm aware about structural rot for boats primarily made before the year 2000. I'll ask the details about that in that forum section.

Assuming I can get them at least to run it on a hose for about 10 minutes, cannot get out my compression tester and check the cylinders, cannot have a nearby boat shop inspect it at my own expense, and cannot get a lake test.

From that, what are the key identifying items other than what I mention below?

Brown water/oil mix after running it up to operating temperature. Likely below the intake manifold.
Rust streaks from sides or back the block or the exhaust manifolds.
Water leaking from the engine period other than hose fittings.
Steam exhaust (Easier to see when engine is warmed up)
The usual bad signs (connecting rod/wrist pin/loud valve train noise)
Shifting issues
Noises around the outdrive.

The going US rate for 4.3L vortec reman replacement with manifolds (parts & labor) is around $7500 correct?
 

Scott06

Admiral
Joined
Apr 20, 2014
Messages
6,451
They should be willing to run and water test the boat. If not assume there are issues. your list of look fors is pretty good. Issue is with no load on the hose doesnt mean much. Conversely if yiu have a successful water test the boat should sell for more. When i sold my old boat 7 years ago i advertised the boat as everything works will do water test. In the end he never asked me to splash it…


Your cost for an engine is low on the lower side. Places like michigan motorz sell reman vortec 4.3s for $3300 plus core and shipping throw in another grand for manifolds plus parts you would be at $7500 easy with labor.
they also sell complete merc reman bobtail 4.3 s for a lot more plus labor…
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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49,585
Motor prices today are about 40% more than they were in 2020
 

nola mike

Vice Admiral
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Apr 22, 2009
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5,366
No reason you can't compression test. 30-60 min. I would also say that I'll buy the boat if a water test checks out...
 
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