As the United States returned to peace following WWII, outboard racing (which had been a rather exclusive and expensive sport with special racing motors) took a completely democratic turn. Because racers weren't getting their rigs out of mothballs quick enough, some race promoters allowed classes for regular fishing motors. Mercury's sleek modern designs had advantages over the most of their competitors and easily won many races.
OMC, controlled by business man Stephen Briggs was stuck on the idea of producing old design motors from their antiquated but functional tooling, maintaining a highly profitable but unexciting operation. Carl Kiekhaefer was very happy with the wins his box stock fishing motors were racking up without any real competition.
Around 1950 relative newcomers Martin and Champion jumped quickly into the high performance fray with small motors equipped with special racing lower units. A small highly efficient motor with a racing lower unit can usually push a very small light boat faster than a much larger heavier more powerful outboard. Carl Kiekhaefer was very aware of this and ordered his engineers to come up with racing lower units for his Mercury outboards. At that time the Mercury line up consisted of two-cylinder and four-cylinder motors from 5 to 25 horsepower. A racing lower unit for each motor size was developed and put into production. Over the next few years the accessory lower unit evolved into a complete race motor package including a shorter than standard short mid section.
Let's start with some background history on the Mercury Mark 30 fishing engine. The 30 was an extension of the existing four-cylinder engine. All of the basic powerhead parts were already in production on the powerful 40 horsepower Mark 55. The Mk30 was made by decreasing the bore to the same size Mercury used on the small KG4 two-cylinder fishing engine. There was some concern that the pressure pulse fuel pumps would not pump enough fuel with the smaller impulse from the smaller bore, so two fuel pumps were installed on Mark 30s for the first year or so. With considerably less power than the standard four-cylinder Mark 55, the larger stronger more expensive Mark 55 lower unit and mid section weren't needed. This allowed Mercury adapt the new Mk30 powerhead to the Mk20 two-cylinder's less costly lower unit, dramatically reducing the cost of owning a four-cylinder outboard at practically no product engineering cost to Mercury. For all intents and purposes the only parts exclusive to the Mk30 were the base adapter and driveshaft. The less expensive but highly attractive Mk30 fishing motor became Mercury's biggest seller and highest profit motor and as a result, the factory could not keep up with demand.
By 1955 Mercury practically had all stock outboard racing to themselves. The smaller classes were dominated by two-cylinder Merc KG4H and Mark 20H; the larger class by the four-cylinder Merc Mark4 0H. This left the middle size C class mostly in a vacuum with clunky OMC products the only possible motors to run in C. With the same basic adaptation of existing parts, Merc closed the gap by adding the Mark 30H to the 1956 line up. The base of the four-cylinder Mk30H was already the same size and pattern as the Mk55H that took over for the 40H so the 30H powerhead fit directly on the driveshaft tower designed for the 55H. Again the 30 did not produce power comparable to the Mk55H, so the Mk55H's lower unit was not needed, the Mk20H's lower unit could do the job. By altering the driveshaft housing to accept the smaller 20H style lower unit the Mk30H again saved racers a few pennies over using the bigger Mark 55H Quickie.
Since the Mark 30H racer would have no viable competition in the C class, no modifications were made to the standard Mark30 powerhead - it just went right on the racing tower with the addition of the direct throttle linkage and small disk flywheel, including the dual fuel pumps used as insurance that the small bore motor could feed itself.
Mercury cautiously estimated the demand for the 30H at 200 units for 1956 even though they had been selling the 20H and 40 cubic-inch four-cylinder 'H' motors a thousand at a time. All 200 were the same Sunset Orange color. The 200 motors promptly sold out. Demand seemed to be building up, so for model year 1959 a second batch of 2,000 30H's was planned. Well, Merc made a mistake in the opposite direction. Just like today, the economy went bad and sales fell off, except not for the fishing Mark 30. The bargain price kept demand chugging along ... fishing Mark 30's were on backorder and most of the 1959 Mark3 0H's were just taking up space in the warehouse. With the 30H powerhead being nothing more than a fishing 30-horsepower powerhead, Mercury cannibalized the racing engines that had not been shipped out. 1,902 fishing 30s shipped out sooner than they would have and Merc sold the lower units and towers at a loss to racers and hobbyists. This capped the 1959 sales of 30H's at 98 and totaled the combined 1956 and 1959 runs at 298 Mark30H's from the factory. Racing started to see declining numbers from the peak years in the late 1950's; APBA eliminated the rule that required Stock outboards to be actual factory production and any of the 1,900 lower units and towers were then reunited with Mark 30 fishing powerheads and became field built 30H clones, legal for racing at a budget price.
In 1962, still another small batch of Mark 30H engines were built. These can be identified by a model serial plate with nothing stamped in the model field, just a serial number well in the 1962 serial number group. All data regarding the actual number of racing motors produced in 1962 has been lost. Since these are very rare, I'd guess that only about 100 were made.
The Mark 30H remained the tried and true APBA Stock racing C class motor from its introduction for well over 30 years when the Yamato 102 motor came to replace it. Modified Mark 30's are still legal in APBA's Modified Division 500cc class and make a presentable showing against the Yamato.
From a distance the Alterscale Mark 30H model starts off as good representation of original. The shape of the cowl and proportions is excellent, and the overall shape and proportions of the mid section and lower unit are generally correct. The decal is correct for the year and highly accurate. The orange-ish red color is also highly accurate for a real Mark 30H. Attention to detail on the face plate is fantastic; all the intricate details are reproduced with remarkable accuracy.
Now let's get critical: the exterior metallic color of the bands above and below the wrap on the cowl are much too sparkly to my eye. The real motors are just bare metal there. Later Mercs had a polished stainless steel band riveted on and a lot of collectors incorrectly paint these areas too. This isn't the most ghastly thing done to the outer appearance of these models. For some unknown reason, the sectional division of the Mark 75H mid section and foot has been incorrectly carried over to the Alterscale Mark 30H and Mark 55H. The split on the Mark 75H model is correct - it follows the true construction form of the rare Mercury racer and divides the motor through the middle of the exhaust outlet; half on the tower and half on the foot. This was not the case with the four-cylinder Mercs made earlier in the decade. The Mark 30H and 55H driveshaft housing is one solid piece from below the lower cowl to the bottom of the cavitation plate.
Apart from the unsightly seam the other exterior errors are minor in comparison. There is a minor scale issue with the black area that represents a slot ahead of the on/off switch/throttle arm. It is a little wide and low. More importantly the throttle cable anchor actually sticks out through this slot on a real 30H, but no attempt at this is made on the model. Above the on/off switch there is a raised section on the model with nothing corresponding on the real thing. Moving to the front of the transom clamps, the Alterscale 30H, like all 1950s Mercury Alterscale models, is missing its model serial plate.
The ends of the tilt tube seem to have a grease fitting applied to them on the model, where on the real thing there was originally a red plastic cap covering the hollow tube. Going rearward to the top of the swivel assembly and the driveshaft housing, no attempt has been made at the "co-pilot" friction disk assembly at all. A very minor but irritating shape pops out on the above water exhaust relief - it is completely cone shaped where the real snout is a cylinder that blends into the housing. Now we'll jump down below that unsightly seam in the driveshaft housing. Just below the split line on the model is the access plate for the rear gearcase attaching nut. The split shape seems to have forced the bottom of this plate all the way down to the cavitation plate. On a real motor you clearly see a flat surface below the access hole.
Moving forward from the access plate we have the front gearcase mounting nut. The worst thing is that the location of the nut is correct for a 55H and a bit off for a 30H with its smaller gearcase. Instead of being placed nearly centered below the swivel, the 30H front gearcase mounting nut is found closer to the driveshaft. The correct nut location is behind the swivel axis, in fact behind the space between the steering swivel and the front of the driveshaft housing. The slot to access the nut is actually proportionally thinner than found on the model, and the nut itself is practically hidden in the slot. I think the nut is also more visible on the model because of the taper put on the model right behind the nut - the real thing doesn't have that taper.
On a real 30H the gearcase fill vent is in the heavy boss that makes up the seal and bearing carrier right below the cavitation plate. It is omitted on the model, but an extra upper gearcase hole was added ... maybe this is to make up for also omitting the lower drain hole. No representation of the water inlet was attempted nor the depression in the case leading to it. It was sort of an NACA scoop inlet below the bullet. A minor bit of scale: the Mark30H gearcase is slightly smaller than the Mark 55H gearcase. Where the 55H gearcase extends all the way to the front of the tower and cavitation plate as the model does, the 30H gearcase comes up a little short. One last thing on the exterior ... the style of the prop was also carried over from the 75H model. This cleaver or semi-cleaver style prop was not used on the smaller motors with any amount of success - and when it was, it was decades later.
Taking the wrap off I see three pretty blatant errors on the ignition side. Number one, is there is no Mark 30H throttle/magneto actuator. Rather than the linkage and throttle advance stop found on the full gearshift models to stop you from shifting into gear above idle, Merc racers had a large triangular stamped metal piece that went directly from the throttle arm to the magneto tower - partly obscuring the magneto from view. Nothing like this appears on the model. Secondly, the model does have some strange feature added to the top of the magneto. I can't tell if it is something that was put on in the fabrication process or if it is supposed to represent an aftermarket add on exterior condenser - whatever it is, it is strange. The third error on the ignition side is the magneto cap. The part of the magneto that sticks out to the front encloses the magneto's internal high voltage coil, but there should be no coil wire going into the magneto at the bottom. In fact, no wires should be going into the bottom of the magneto cap at all – the spark plug wires should be exiting the side of the bottom edge facing the throttle, not the bottom.
Also, there are no towers on the magneto cap as portrayed on the model. Minor details include three vent hoses when there were only supposed to be two, and they should have run to the bottom front where they attach to a baffle assembly low in the cowl. One other ignition component bothered me for a while and I could not figure out why for almost a week, and then it dawned on me: the spark plugs are black - all black. I'm sure it would look more realistic if the part below the rubber boots was metallic. Super realism would have included a ring of white to represent the porcelain insulator. One more detail on the magneto side before we go to the fuel side - another accidental carry over from the Mark 75H, there is the representation of an ignition ballast resistor bolted to the side of the exhaust cover - correct on the 75, wrong on the 30 and 55.
On the fuel pump side the model again suffers from carry over from the Mark 75H model. There should be no bearing oil scavenging hose going to the boss feeding the center main bearing on any pre-1960 Merc. 'Red Mark' 30H's came from the factory with 2 fuel pumps. Little attempt at accuracy is found on the fuel lines at all, nor is there any attempt at the true shape of the fuel pump. A fancy bit of realism would have been a touch of brass color on the choke shutters. The shape of the carburetors is basically correct for the Mark30H, even though they were wrong on the Alterscale 75H, 55H and 55H with stacks.
I have two more complaints - if you look up into the top cowl at the flywheel you see a starter ring for an electric starter. None of the racing Mercs used this type of flywheel. The Merc racing motors used a small disk at the top of the crankshaft that attached the "basket" for the pull starter dogs engage. Lastly, Mark 75H, Mark 55H, and Mark 30H engines all came with the blocks painted white, not bare metal or silver paint.
Does this mean the model is not worthy of a collection? That depends on the collector. As an outboard engine enthusiast, I would like to have one of these on my desk. Many hardcore collectors may not think the same, however I think the model still looks fantastic, despite its historical inaccuracies.
Thanks to Sam Cullis for his valuable contribution to this feature article.