personally I wouldnt dead head it
run a fuel manifold for the carbs, have the fuel return to the tank and get the type of regulator you can install on the return line.
but before you spend the money some full load pressure tests might be the go once you get the dyno set up.
Let me throw out a thought or two on ignitions. From the time we were playing with Merc V-6 tunnels running the same style ignition used here, we found the surface gap plugs would have a high speed miss which was solved by going to a conventional gap style plug. We were running gas at around 9K+ rpm and the ignition was only firing one coil & plug per cylinder. My thought would be to try a conventional plug. All the pics I've seen only show surface gap plugs. The second observation comes from playing with a 125 cc VRP motor as well as a friend playing with a 125 Honda shifter kart. We were having a horrible time to get the 125 VRP to plane off. That changed after the spark plug gap was reduced from 0.018 to 0.012. With Mercury ignitions we were always trying to run larger gaps but the small alcohol motor works great with a tiny gap. So I relayed that to my shifter kart friend who tried a much smaller gap on his Honda and he was ecstatic because it cured a persistent high speed miss that they had for some time.
My thought would be to try small gap, conventional style plug, preferably with a fine wire center electrode to minimize the voltage needed to fire it, before getting sidetracked with fuel flow ideas, etc. 60/66 cubic inch loopers worked with 3 pumps and 40/44 used 2. Add the two together and you get 100/110 cubic inches and 5 fuel pumps so this should be fine.
I am sure you are aware, but those Mercury black stators (with low and high speed windings) are very prone to failure on the high speed side, thats why they switched over to the "red stator", which combines the low speed and high speed windings...........MUCH better and reliable stator................just a thought.....that ADI ignition system is a very good system, considering it does not require a battery...
Daren Goehring
63-R
DSH, 500ccmh, 750ccmh
In as much as it has been pretty quite and just for some activity I thought I would just insert the ongoing work to produce the dyno for testing the beast before making a fool of myself again.
I have the old Land and Sea prop shaft dyno that I had setting around from my dealer days to use as the unit to absorb the torque. Not wanting to load the prop shaft of the SSM, which has the opposite rotation as the pump, I decided to make a power head stand.
Wanting to turn the engine around 8 to 9k, it need to have a reduction box. The pump as used on the prop shaft was running at about 3k max. Much more and cavitation may start. I decided to make it simple and use a chain reduction.
To get some meaningful information, which is difficult with just hydraulic pressure I am mounting the pump to a 12 inch torque arm that is mounted with a bearing between it and the reduction box. This will, with the pressure scale transducer, allow a direct read from the pump in foot pounds of torque.
I have inserted a couple of drawings of the basic assembly that is being constructed and pictures of some the work in process. The pump adapter shaft will have a bearing at the upper end of the shaft that seats in the bore of the torque arm bearing. That downloaded cad file of the bearing would not print out in the drawing. It will prevent any side loading of the pump shaft.
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Hey Dick,
You underestimate the value of your Hillsdale testing. The Looper Beast started easily and planed the boat. You learned the mixture is too rich and there may be a spark problem, but best of all, nothing broke. At Fairlane Boats & Motors in the early 1970's, we tank tuned numerous Mercury sixes with adjustable jets (on test wheels). It was a balancing act with only three carbs on gasoline; with procedures well defined by Kiekhaefer. You build a fabulous Beast with experimental everything, and on methanol. My guess is six modified carbs with adjustable main jets is the issue: 15 minutes on the dyno and you're golden.
Tim
Tim
I too built a Dyno from a Land & Sea unit. Mine however is not nearly as cool as yours will be… I used a 2:1 OMC service unit in reverse gear to slow down the pump speed. I also called a tech rep at Land & Sea and asked him about the pump speed. For some reason he knew I was running race engines on it… Go figure, right? He implied that 5,000 rpm pump speed would be fine, as long as it wasn’t extended durations of time. He also expressed that the oil lines should be in good condition. Because imagine the pump turning nearly 4500 rpm at 3500 psi of pressure and a line exploding on you! That’s a lot of oil ALL OVER THE F’N PLACE!
I also added a load cell at 12” to measure torque. I considered putting it at 6” since I have a 2:1 gear. So with this setup, I use all the original pump adaptors and it mounts right the engine right on the boat. Primarily I did it this way for the Stock Outboard applications such as the Yamato 80/102/302’s, 44xs, and Tohotsu applications with tuners in the tower housings.
The only problem with a having your own Dyno is… Work creates more work…
I will post pictures soon,
J-Dub
At the speed the chain would be running. I would rather see a timing belt instead of the chain, for safety sake. Hope it works well
December plus winter weather is a tough time to get much done. I have made some progress on the dyno and have attached a few more pics of the progress. I did after some thought and speed calculations change my mind and switched to belts. Plural on belts because I made the shafts extend out the bottom to add a second belt for backup. Don't want one breaking and letting engine go. Just got the large pulleys this week so I can take apart and do final assembly.
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very nice!
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