TOPIC: Mercury Mark 30 weak lower unit?

I picked up a 1956/1957 Mark 30 yesterday that is in good shape (no dents, sounds great), but I've been reading they have weak lower units. Is this true and why?

I have two Mark 25s and I noticed they have the same lower unit as the Mark 30, does this have something to do with it?

I'll post a picture tonight.

Unless someone else knows differently,...The Mark 30 lower unit should give you good service provided you keep the gear lube water-tight, and don't hit any logs or dig any clams with it.
Typically, the steel drive shaft & prop shaft can develop rust issues where the seals need a good smooth surface to seal against, but you can 'fix' those areas by installing stainless 'speedi-sleeves' & new seals.
Looking forward to seeing pictures.

doc F

doc is correct. have been run on dirty 30's 40-44cid.without trouble.

"have been run on dirty 30's 40-44cid.without trouble."

Haven't heard that phrase for a LONG time!

doc

Glad to hear there aren't any major issues with it!

Pictures as promised:

Side



Front



Next to my '61 Merc 500



With the rest of the family

That's a cool motor! Years ago I picked up a MK30E and was impressed at how smoothly those teeny weeny pistons ran & how it revved up smartly. Wished I had kept it, but do have a couple other non-electric ones kicking around in pieces!

You may have heard talk of a weakness in the MK30H mid-section, the slot for one of the lower unit studs is deeper than the A/B & D Shortie mids, and tends to crack after hard racing.

I also remember a posting about the "C" racing unit breaking driveshafts at the pinion gear and resultant destruction of the lower unit, but again you're talking about racing stuff which is highly-stressed.

Can't recall any big issues with the standard MK30, nothing out of the ordinary.

Cheers.......ed

Thanks for all the info Ed. I'm fairly familiar with the OMC's from this era but am just getting into the Mercs, lots to learn. It must have been the racing Mk 30's I'd heard of with weak mids/lowers.

You had a nice looking motor also! Did you paint it?

amreame wrote:

Thanks for all the info Ed. I'm fairly familiar with the OMC's from this era but am just getting into the Mercs, lots to learn. It must have been the racing Mk 30's I'd heard of with weak mids/lowers.

You had a nice looking motor also! Did you paint it?

That's not mine, just a pic I gathered from the internet....ed

Amreame

Sweet looking Mark 30 you have there, your looking at a racer in that pic Mark 30H. Great job on finding that Mark 30. Looks like it's about time to change your avatar!

Travis

Thanks Pondrocket. The Evinrude Fastwin is what got me started in this whole boat building/restoration deal.

If you like my Mark 30 then I'm assuming you'll like what I picked up over the weekend. Not sure how long it's been sitting but there was a thick coat of grease and dust on it. Compression is good but I haven't gone through it yet.

looks like it has the original carter carb onit. leave it original just clean it up well. looks in fantastic shape.

Thanks, I don't plan on doing much else to it besides some degreasing cleaner, at least for now. I'm going to pick up some reading material this week, I really don't know much about this motor.

Sweet great find. Are you in any of the local chapters of AOMCI in Michigan?

Travis

No I'm not a member, yet. I usually bring some motors to any boat shows I goto but haven't been to a purely outboard show in a few years. I checked the AOMCI calender and it looks like there's an event in Traverse City towards the end of the month that I might check out. I'll also be at the Spring Lake Boat Show which is around that time too.

I have 5 motors in pretty good condition that I wouldn't mind taking to one of the AOMCI shows though.

Sounds Great. Hopefully you can make the Suter meet and the end of the season its a pretty good meet. I'm in the metro Detroit area and a member of the Great Lakes Chapter. Let me know of any meets you attend I might be at them.

Travis

Thanks I will. I took another look at the calender and it looks like the Constantine Super Meet is the big one to look out for.

I will be a Constantine hope to see you there. I will have my Zip there with the Mighty Mark 58.

Travis