Magnesium decks

viperv10

Well-Known Member
Joined
Oct 7, 2016
Threads
45
Messages
171
Does anyone know when Lawn boy stopped making magnesium decks? I'm always looking for old lawn boys to fix up and I see a lot that are advertised as magnesium decks. Some of these are with F engines from the 80's that are probably aluminum. I was just wondering when they switched. I remember seeing some 60's style mowers with magnesium stamped into the deck about where you would put your foot to start the mower.
Do you guys have any knowledge about this?
Thanks,
Jerry
 

John Fitzgerald

Well-Known Member
Joined
Aug 22, 2018
Threads
8
Messages
156
They were likely a magnesium-aluminum alloy. Pure magnesium wouldn't work for a deck. Even the alloys tend to corrode, so are not much used any more.
 

bertsmobile1

Lawn Royalty
Joined
Nov 29, 2014
Threads
64
Messages
24,647
Magnesium based die casting alloys are generally Mg - Zn alloys rather than Al
Mg - Zn gives a much better casting with less porosity & shrinkage.

It gets confusing because we erroneously call Al -Mg alloys used for wheels , mags
 

rfWi

Active Member
Joined
Oct 6, 2016
Threads
7
Messages
61
I currently have 3 mag deck Lawn Boys.2 1970's era D-engines and a 1992 M-series.I did have a 1965 mag deck too.All have magnesium stamped on the decks.I don't think F-engines had mag decks.I believe the M-series with mag deck was made until the mid 90's.
 

Lawnboy77

Well-Known Member
Joined
Apr 18, 2016
Threads
1
Messages
193
I believe OMC Lawnboy changed over from mag alloy to aluminum around 1977, with the exception of commercial LB decks, they were always cast aluminum to the best of my knowledge. I was talking to a long time employee of OMC Galesburg a few years ago and I think I remember him saying that the commercial decks were only available in cast aluminum due to aluminum being less likely to crack and not as prone to severe corrosion like the mag alloy decks. They wanted max strength and longevity in the commercial line. The 1977 residential mowers are a mixed bag, some I've seen some that were aluminum, and some were mag alloy. As far as I know the F series mowers never came with mag alloy decks stock from the factory, and they started production in 1978. Later on down the road after Toro bought LB they started producing mag alloy decks again with the M series mowers (1989 to 1996).
 

viperv10

Well-Known Member
Joined
Oct 7, 2016
Threads
45
Messages
171
Thank you for the info. I think it would be great to know a long time employee or and engineer from lawn boy. I bet they could give you tons of useful info and tell some pretty good stories too. I think some people just say magnesium decks just because they are cast and not stamped steel. I don't mind a steel deck.
They seem to be very light also. The lightest and easiest to push mower I have is a 1980 R7070 with the yellow shroud, wheels and handle grips. It's a cast deck and a dream to trim with under my pine trees.
Thanks again.
Jerry
 
Top