Mercury Mark 40-H

[Aeroliner]

I do beleive that Mercury sold the "Q" and "H" towers as a complete seperate package and a KG-9 became a KG-9Q. Likewise for the A and B motors had a hydroshort unit that could be acquired for the two cylinder engines. So if you bought a quicksilver "H" lower unit package from mercury and installed it on a Mark 15 it became a mark 15-H. Likewise for the KG-4 and KG-7 engines which used the same tower and foot. So if you put a Mark 58 on a H tower it becomes a Mark 58-H. Now don't confuse these engines with there name tag versions in that Mercury promoted both as racing engines and the use of quicksilver equipted engines was very common in APBA racing.

Alan

[Mark75H]

No, it did not completely work like that after the year 1950.

You could put a "Q" under the original motors ... but not for the "H's" the only exceptions were the Mark 15 over the AB H tower and the Mark 30 over the "salvaged" Mark 30H towers. Even though you could race the motors that way, it did not make the motor a "Mark15 H" or a Mark 30H"

There are actual known serial number groups for most of the "Q" and "H" motors ... other pieces put together are just parts that fit together, not 55H's 58H's, 15H's or Merc 28AH's. Where would the line be drawn? Is a 2 cylinder Merc 350 with a 55H tower and foot a Merc 350H? Is a Mark 75 adapted to a Mark40H tower and foot a Mark75H? Is a Chevy Caprice with a Corvette motor a Corvette or a Caprice?

Racing rules were and still are very strict. A Mark55 fishing powerhead would not have been legal before they changed the rule in the late 1960's ... it would be out of spec on the ports and if you changed the ports to meet spec, the machine work would be obvious. Russ Hill or Edgar Rose would throw you out, no apology. If there was any doubt, they would have consulted the serial number lists.

Merc did sell loose Q and H towers, but they went into use as alky conversions, replacements for damaged racing parts or cottage racers. Outside the 2 exceptions I noted above ... H's could not be "made" outside the factory doors.

[Aeroliner]

If the engine did not have an H in it S/N tag then its not a factory racing engine. But others built still falls in the class of engines, i.e. engines equipted with the racing tower would be considered as a racing engine. Factory engines or parted together made legal racing versions reconized by APBA. While I owned my mercury dealership I put together a number of 20-H conversions by ordering all the parts right out of my parts catalogue. I beleive that these engines are a factory 20-H even though they don't have a S/N tag and were not assembled by Mercury. Mater of fact the blocks came unstamped with a S/N.

Alan

[Mark75H]

Very correct on the possibility of a "replacement part" motor ... many of those parts have such specific or peculiar shapes, stampings, die marks etc that the inspectors knew and know when they see them. Every part is on the parts list for the specific race motor and approved by APBA and NOA if different from the original. I'm stunned that you had the time to give away or your customers had the cash to afford the labor to hand assemble a "new" race motor compared to just buying a very good used motor.

But there is no Mark 58 H parts list, no Mark 15 H parts list, no Merc 350 H parts list.

A fishing motor equipped with a racing part, is a fishing motor equipped with a racing part; it does not "become" its racing cousin.

[Silas_53A]

weather they are factory race engines or not, they still make me drool... they are beautiful!!!

[Aeroliner]

We are nearing completion on the KG-9Q and will be posting photos soon. I have a 75-H question. I have been told that the very early Mark 75-H engines had KA-7A carbs and that the later engines came with KA-6A carbs and could run fuel or gas. Can anyone verify this because I found a mark 75 with KA-7A carbs in a bunch of parts I just bought.

Alan

[Mark75H]

The KA6A's are the only carbs on the Mark75H parts list, but both KA6A's and KA3A's are listed on the spec sheets. I have seen several sets of KA6A's and know of a few more, but have never seen a KA3A. KA7A's are not listed as legal carbs on the spec sheets.


What kind of lower unit and mid section does this motor have? Quicksilver? Speedmaster? 75H prototype? production 75H?

Do you have any pictures? Does any thing have a serial number on it? The 75H serial number group is pretty specific.

[Aeroliner]

Hi Sam,
It is only a powerhed so far. I still have to clean out the barn. Bought a ton of mod items and it will take some time to get it sorted out. Still have to make two more trips at least. I might find a lower unit in the parts. I will provide photos as soon as I pick it up. Thanks for the info. I was only aware of the KA-6A's but KA-3A are new to me.

Alan

[Mark75H]

Originally Posted by Aeroliner

It is only a powerhed so far. I still have to clean out the barn. Bought a ton of mod items and it will take some time to get it sorted out. Still have to make two more trips at least. I might find a lower unit in the parts.

Well, with just a powerhead, you should have a serial number to start with anyhow. Hope the next trip hits gold!

[Jeff Lytle]

Very VERY nice restoration work!