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High cubic inch OMC engines made back decades ago used cross flow designs with ignition points unlike todays engines with Capacitor Discharge Ignition Modules which are marvelous.....just plugging in a side note here and surely part of the MPG equation.Thanks for the information. No issues with my motor, hopefully it will keep running for another 35 years. I was just reading that some people prefer one type over another for efficiency I think.
Regards
Leachy
Here is a picture of a Holmes plywood boat like the ones described herein, built in Houston, Tx. Superb bay boats for Galveston bay because although the mornings were calm with slow rolling swells, in most afternoons in the summer the wind would pick up out of the South and it was a rough, wet ride....if you didn't have one of these with a canvas top....I didn't, rented boat, 10 hp engine, one hand on the tiller and the other on a can baling.....no brag just fact.....being a kid I just thought it was fun....not scary!High cubic inch OMC engines made back decades ago used cross flow designs with ignition points unlike todays engines with Capacitor Discharge Ignition Modules which are marvelous.....just plugging in a side note here and surely part of the MPG equation.
The cubic inches produced great torque at lower RPMs which powered many a fishing boat full of gear and folks. I mean a pair of 35 HP Gayle, Johnson, Evinrude and a few other spinoffs of their design would power an 18' plywood semi-V with 2-3 fishermen, and all their gear at probably a 30 MPH clip....estimated by wake and boat attitude in places like Galveston Bay (Tx.) where I spent a lot of time as a youngster. I learned to water ski behind my 18 HP rude on a 13' boat.....no game changer, and was with 2 skis, but it got me out of the hole and I had fun.
Problem was that they were thirsty. Since HP = (Torque x RPM)/5252, Mercury decided to go after the RPM side of the equation with low cubic inches and high RPMs. OMC patented the "Loop Charged" scavenging system racer mentioned back in '68 (model year) as I recall with the 55 HP 3 cylinder Evinrude Triump. It was a game changer and realizing that the Loop scavenging system produced superb MPG soon everybody wanted to be on the bandwagon.
Since OMC had a patent, Merc had to come up with a solution. They kept the crown on the piston but redirected the cylinder charging path, similar to the looper and called it Direct Charge. I had a 115 I6 built in that last production year of the I6 (1988) and it stood up to OMC in power and economy even though it was running a HP per cu. in, but at much higther RPM than the OMC engines.
By 1989 Merc had a totally different engine lineup and almost all were Loop charged (OMC patent had expired). I currently have a 2002 115 Merc 4 cylinder looper and It is strong on power, and low on fuel consumption. I love it.
Reference: My memory....at 81 you can guess just how accurate it is.....grin
I recall seeing pictures of what I said! That is why they called it "Direct" chargingThe Lawn boy power mowers ( OMC product ) had loop charging in the mid 1950's----So it was not a new concept in 1968.-----Casting techniques allowed it to be incorporated in multi cylinder motors.---Direct charging was just a marketing term.-----Nothing different on the pistons.-----But I think the crossflow engines benefit from easier to inspect / repair design.-----Modern motors run great, but difficult for the backyard / DIY individual to diagnose !!
I had one and on my Ranger I had a 10 gallon gas tank and I could fish all day running large Texas lakes on a tank of fuel. It had much better fuel economy of my previous OMC cross flows. I had it 7 years and sold it to my SIL and only thing other than plugs was the rear water jacket cover jacket started leaking and I replaced it...impeller was original.I recall seeing pictures of what I said! That is why they called it "Direct" charging
Then why did I see a hole in the side of a Direct Charged Piston that cross flows don't have?Direct charging was a " marketing " term.-----The OMC loopers ( 3 cylinder 55 / 60 HP ) were selling really well.-----Mercury had to come up with a term that sounded good when explained by a dealer trying to convince the buyers.
Yes the crown was still on the piston just like cross flow pistons. Unless you have all the exhaust tuning that comes with the looping process you need the crown to keep the bang in the cylinder long enough to get power out of the fuel mix.Repeat.------A marketing term called " direct charging "-----And direct charging still has the deflector on the piston.-----Loopers are generally a flat top piston.