Mercury Mark 30

[mgsolakis]

Was looking at a Mercury Mark 30 for my Mahogany boat but the gentleman selling it says it has an issue. He says the issue is "shift mechanism, clutch and forward gear ramps." Is this a lower unit issue?

Thanks

[billw]

Yes, what he is saying is a lower unit issue. Pre-1976 Mercurys are well know for failed lower units, due to rust from water intrusion. The shafts were steel, not stainless; and they pit, tearing the oils seals out. That being said up front, I have never, ever seen the clutch RAMPS of either the gears or sliding clutch WEAR out. I have seen a couple of totally shattered clutches but never worn. Shift issues on Mark 30s are usually related to the shift linkage itself. They shift with a twisting motion. This motion is often lost due to spline wear, incorrect reverse lock adjustment, twist-distorted shafts or all of the above. Sometimes, it can be as simple as someone putting the lower unit on and not lining up the shift shaft splines properly. Best way to tell is to pull the lower unit off and see if it will shift when not attached to the rest of the linkage.

Long live American manufacturing!

[mgsolakis]

Thanks Bill, does this sound like a dangerous buy? I do have someone local with a replacement lower unit if it is just a lower end issue.

[jw-in-dixie]

Mark 30 is a nice, smooth motor and I love them. They do tend to have shift issues, tho. Like when it’s running in neutral it might just shift itself into forward at a bad time. But it’s nothing that can’t be corrected if parts are available.

[billw]

Price and your mechanical skill/patience level, are your biggest factors, in whether you buy or not. Mercurys are not impossible to work on but tend to get more involved than OMC stuff, as a general rule. I have worked a lot on both products, both as a hobby and professionally. I have found this to be a fact. Old Mercs are also not good at ALL in salt water; so don’t even THINK about that. (New Mercs are fine.) However, like JW says, they are good running, smooth engines, when right. I know I would not likely turn down a Mark 30….

Long live American manufacturing!

[Author]

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