Kr or kc strangler or stinger

[Bill Gohr]

I have 3 real KR's apart right now if you want to see some pics

[Mark75H]

Please

[MTECHMARINE]

I stand corrected, the later pistons with 3/4" pins will NOT work in the KC motor
, the wrist pin was relocated, longer rod used.
KR has 3/4" pins already.

[brichter]

Right, the 1973 (p/n 385510) rods have the 16 roller bottom and the top sized for the 3/4" pin however the '73 pistons go too high and hit the head, the '74 and later pistons will hit at bottom dead center. You get into machine work, pistons and ports.....Both things have been done but its a pain.

[194265]

Built this engine in the summer of '05 and installed it on a 1972? Marlin Sidwinder. As some of you might remember, I worked for OMC back in the late 60's and early 70's. Anyhow a stock 115 (96.2 cu/in engine) was rated around 106 HP at the prop shaft and would good for upper 40's on a high performance boat of its day (I am quite sure i'm going to take some flack on that statement). Attached some pictures of some of the changes I made, don't use these large ports with the later keystone ring !!!!! I also used the 140 HP intake manifold, reed block, reeds and stufferblocks. I tried 1 3/8" carbs, but never quit ran right, went back to 1 5/16 " carbs with adjustable idles. End results was 5700 - 5800 RPM with a stock 23" two blade (non cuped) brass prop. Thats, with a .1 % slip 58 MPH. Also built another one in the spring of '07, will go into detail later.

[milkdud]

WOW!! holy big ports.

[Mark75H]

When you don't have as many, they have to be bigger

[Bill Gohr]

Those might look normal to some

[stinger]

Gday Bill.Would love to see the KR pics.Sorry Ron ive been very busy,summer here,will post pics of KR motors and parts and props soon.Ian Purdon,Reg Sorenson and Bert Hines,all ex omc racers say hello.Nice work 194265.I am rigging my old modified F3 boat with nice fresh FR31M Power for the series here.Peter.

[194265]

I started with a 1975 OMC 135 block and made the following changes. Reworked the porting as shown, did not change port timing. I then removed the cast water line that takes water from the block to the exhaust cover and welded up the hole in the exhaust cavity. I cleaned up the rod slots so that I could use the later rods and pistons with the larger wrist pins. The pistons I used are the low ring pistons (as you know I am not a big fan of the OMC Key stone ring). The piston skirt was notched like 115 piston in the above article. Used the '73 heads and ended up with an average compression of 136 PSI per cylinder. I then ran an outside water line (rubber hose) from the water inlet side of the block to the exhaust cooling cover. I again used the 140 inlet maifold , reeds, rubber stuffers and 1 3/8" carb. Again the large carb gave me problems and went back to the 1 5/16 carbs. End results on same 16' Side winder, 6200 rpm, 24" SS three blade cuped prop was 62.9 with .10 % slip. As you know, Side Winders tend to be nose heavy, gave the whole rigg to my son. He's going to put a six inch set back on and see if he can get the nose up.