Hydra Mac 8B Onan Identification

[Friesen009]

Hello everyone. I have read over quite a few posts here and it seems that there are many knowledgeable people around here, so I figured I may as well join in. So here is my current issue. Just recently bought an old Hydra Mac 8B (plan a restore in the future with new motor), thing runs great for the most part, but obviously need some TLC here and there for the time being. I was going to look up some parts for the motor and low and behold someone had drilled the rivets holding the identification plate out. So I have no way to identify the motor. I was just curious if anyone has any idea what model of Onan motors were installed into Hydra Macs. I do have a few pieces of info which may help. Skid Steer Identification Plate States : Model - 8B Serial No - 4132 Engine No - NHC-MS and Intake Manifold # - 170-2966 There are some seals and such leaking on the motor which I had hoped to replace while I play around before next winter and the restore, but I would like to be sure that I am ordering the right parts. Any information would be appreciated. Thanks in advance.

 

[flyerdan]

Grab yourself a copy of the Onan NHC family repair manual. It should outline the differences in models and you can compare to what you have.

 

[Friesen009]

Grab yourself a copy of the Onan NHC family repair manual. It should outline the differences in models and you can compare to what you have.

I had a copy of that and took the search a bit further (for anyone who may be looking in the future, here is my best guess so far). After doing searches on the Gehl 2500 and Ford CL20 which I believe to have run the same engine I came across the "Onan N Series Training Manual". It seems that sometime back in the 70s Onan's N series engine were all the same (except the N52M). They all came as 2 cylinder 4 stroke engines with a bore of 3.56", stroke of 3.00", and a compression of 6.5:1(NHA) or 7:1(NH, NHB, NHC) with 60 inches of displacement. The N52M was an odd duckling. It wasn't until later that Onan changed their model and serial system. This is where the B, P, and T models which I have been seeing for most parts lists come in. The B seems to stand for Basic (just guessing), the P for Performance (actually stated as such), and the T for something I am unsure. The B and P series seem to often times be lower HP engines with a different bore and stroke. Best that I could find is that older John Deere F930's ran an Onan which when cross referenced with the NHC from this manual had identical bore, stroke, displacement and HP. So I am guessing that the Onan T260 which was used in the John Deere F930's is an updated version of the NHC from the 70's. They may have some minor option differences, but are fundamentally the same engine. I have found a decent supply of parts for the T260 from Sears Parts Direct.

 

[12CHydraMac]

I had a copy of that and took the search a bit further (for anyone who may be looking in the future, here is my best guess so far). After doing searches on the Gehl 2500 and Ford CL20 which I believe to have run the same engine I came across the "Onan N Series Training Manual". It seems that sometime back in the 70s Onan's N series engine were all the same (except the N52M). They all came as 2 cylinder 4 stroke engines with a bore of 3.56", stroke of 3.00", and a compression of 6.5:1(NHA) or 7:1(NH, NHB, NHC) with 60 inches of displacement. The N52M was an odd duckling. It wasn't until later that Onan changed their model and serial system. This is where the B, P, and T models which I have been seeing for most parts lists come in. The B seems to stand for Basic (just guessing), the P for Performance (actually stated as such), and the T for something I am unsure. The B and P series seem to often times be lower HP engines with a different bore and stroke. Best that I could find is that older John Deere F930's ran an Onan which when cross referenced with the NHC from this manual had identical bore, stroke, displacement and HP. So I am guessing that the Onan T260 which was used in the John Deere F930's is an updated version of the NHC from the 70's. They may have some minor option differences, but are fundamentally the same engine. I have found a decent supply of parts for the T260 from Sears Parts Direct.

If you have Facebook I have a group for these machines... www.facebook.com/groups/hydra-mac Would like too see you there. Lots of guys in that group with 8Bs, 8C, some 8As... etc