Our Roamer came originally outfitted with Ford 427 gas engines–the same basic engines that powered the famous GT-40s that won Le Mans. While the mighty 427 is a great motor, with 300hp each side, even the relatively lightweight aluminum Roamer hull is a lot to push around. The original owner had the boat repowered in 1973 to Super SeaMaster marine power: 534 cubic inch Ford Super Duty engines with twin turbos and an intercooler. The Super SeaMasters developed 400hp at a relatively low 3200rpm and 657 ft/lbs of torque. Very wild stuff for the early 1970s!
The Super SeaMasters were trashed from water ingestion when we obtained her in late 2007 and, having always been a diesel boat guy, I decided to repower the Roamer to diesel. While many of these 46s came with Detroit Diesel 8V-71 power, and I like Detroits, they’re not very economical, clean or quiet. I was interested in trying something else, especially since we do most of our cruising at hull speed. My thinking at the time was, why put three tons of Detroit in to get 600 max combined hp, most of which I don’t use? After talking this over with some yacht club friends, a world-cruising sailor recommended 120 or 135hp Ford Lehman engines. According to online calculators, combined 240hp is more than enough to push the hull along at 9kts @ 6gph. That sounded pretty good, especially since Lehmans with gears could be had for relatively cheap compared to newer, higher powered engines.
So, Lehmans it was!
The carburetor sits at the back of the engine, just above the marine gear on a water-cooled plenum. The turbos, which were only oil-cooled(no water cooling jackets!), drew air-fuel mix from the carb and pressurized it, pushing it through hoses and chrome tubing up to the water-to-air intercooler on top of the intake manifold, where the carb would normally go. If any hose clamp let loose on the pressure side of the system… Hold onto your britches, Ethyl, we’re goin’ to the moooon!
An online inflation calculator tells me that $6,480 in 1973 equals roughly $33,500 today…and that was the price for EACH engine.
Most of the damage to them was caused by being unloved–especially the part about being drowned repeatedly–while in Purgatory Row at the southern Maryland boatyard for two decades. I tried to sell them on ebay and craigslist, but got no nibbles; not surprising, since they were long-since obsolete. So I loaded them up and took them to the scrapyard. Since I’m a big fan of neat, old mechanical things, that was a sad, sad day.
The blue thing in the lower part of the picture is the watercooled carb plenum, which sat at the back of the engine over the marine gear. The blue thing with the two holes in it at the top is the intercooler.
All of the SeaMaster castings were things of beauty.
Removing the spark plugs revealed that each cylinder was packed full of rusty sludge. These things were never designed for submarine service.
Again…even the best turbo hardware on the planet (circa 1973) wasn’t rated for submerged service.
Out came the galvanized steel original tanks (diesel and zinc don’t mix).
And with that, we (mistakenly) put a check in the box entitled Install Engines…but more on that later. One teaser hint: never, ever trust a sailor when the topic is repowering a planing powerboat! 😉