Old K&B 7.5 Marine IB won't start

[GHaycraft]

This engine, circa 1990, is a rear carb, front exhaust engine with red anodized carb. Engine Serial # A0004945. The carb has only the bent wire high speed adjustment, and a barrel stop screw. There is no idle adjustment. The carb has a fixed air bleed hole on the under side. The engine has a tuned pipe without muffler pressure. The original engine insturctions say muffler pressure isn't needed, and also state that the needle valve should be open six turns to start. I don't know if the engine was ever started/run when new. I was recently given the boat to see if I could make it run. javascript:emoticon(':evil:') The engine turned over, but frequently stuck at TDC, typical of the ABC type. It's plug was dead, and I only had a short idle bar plug, so I tried it. The engine did eventually start and run for 5-10 sec. that afternoon, but refused to start again. Since then, over three or four afternoons, it has never hit again. The engine now has a long, non idle bar plug that glows well. It was disassembled and reassembled after the first session. The engine interior surfaces looked fine. Reassembly is absolutely correct. The liner matches the exhaust and intake channels. The rotary disc valve is correct. The carb sucks when the engine is turned over. I get good turn over with a Sullivan 12 volt starter motor and drive belt. The engine will still occasionally lock at TDC. Fuel tank and lines checked for leaks/air holes, none found. Fuel is fresh 25% nitro. Glow plug is run from a power panel with meter, so I know we have heat. Have tried starting with/without the tuned pipe. With starter motor turning the engine, glow plug is then heated, and fuel line unclamped. Needle can be adjusted from "dry" exhaust to "wet spray with droplets" exhaust and it still doesn't fire. I have now noticed one of the four ears for the backplate mounting screws has cracked off. There appears to have been a bubble in the original casting at that point. The gasket is still good, and the screw holds the remainder of the mounting hole snug enough, for now, I think. I hesitate to put the cost of a new back plate/disc valve assembly into this engine if it isn't going to run at all. I've been into R/C planes of all sizes since 1970, but this is my first marine engine. I've run out of things to try with this engine. Assembly is correct. Compression feels about right for an ABC engine. The plug is correct, and hot. The fuel is fresh. The fuel tank and tubing are not leaking, properly hooked up, and vented. The carb has been dissassembled and is absolutely clean. The engine turns over well with the starter. I can adjust the mix anywhere from lean to flooded while the engine is being turned over with the plug hot, and nothing happens. Any ideas from the experts? ?javascript:emoticon(':roll:')

[nitrorc5]

well first off 6 turns is not good
try 4
also check the line if it has fuel but than loses it than instal a pressure nipal on the header to the tank
if your geting droplets of fuel and its hard to turn over your flooded
the 4 turns will help but if yu screwed up your rod from trying to start it flooded you cant do much use the setingings i told you after you take of the glow plug and try to start it by using the starter untill you dont geteney fuel coming out of the head than put the plug back on DONT PRIME IT if your engine starts reves and dies do what i told you about the nippal to get costant fuel
also check comprecion wiith no fuel in engine if its realy easy to turn it over with your hand and you dont haer a stroung pop(with the plug on ) with the header off you dont have comprecion

if you whant call me at 561 827 1897 so that you can explian this beter