seafever
Seaman Apprentice
- Joined
- Dec 7, 2013
- Messages
- 33
Stilll fighting the same battle - the question is Is The Block cracked?? (We get 40 below zero here)
boat is 1974 Silverline Antigua 18T, engine is mercruiser 888 (302 ford)
Problem: Overheating at higher RPM not WOT
SO FAR have replaced impeller pump and seals in lower unit, pulled heads, magnafluxed and planed, replace both exhaust bellows, replaced water pump, no evidence of water in oil. no obvious coolant leaks. replaced all coolant lines and checked for blockage. have run with water muffs and drive in a tank, also did a river run
I installed a 1" clear plastic section in the cooling water inlet hose. When engine is started and idling, coolant flows to and from engine. At higher rpm temp starts to climb and water goes backwards through intake line against impeller pump. Then air in intake line (Exhaust??)
My theory= block is cracked internally allowing exhaust pressure from a cracked cylinder into the water jacket???
Where else could that kind of pressure build up? How can I check this without pulling the engine? Dye check the cylinders?
Thanks, I been 2 years on this problem, right now it is minus 28 degrees so lotsa time for more research before spring, and no shop to work in... lol
BTW the hull serial number is 001 is this the first Antigua out of the mold??
boat is 1974 Silverline Antigua 18T, engine is mercruiser 888 (302 ford)
Problem: Overheating at higher RPM not WOT
SO FAR have replaced impeller pump and seals in lower unit, pulled heads, magnafluxed and planed, replace both exhaust bellows, replaced water pump, no evidence of water in oil. no obvious coolant leaks. replaced all coolant lines and checked for blockage. have run with water muffs and drive in a tank, also did a river run
I installed a 1" clear plastic section in the cooling water inlet hose. When engine is started and idling, coolant flows to and from engine. At higher rpm temp starts to climb and water goes backwards through intake line against impeller pump. Then air in intake line (Exhaust??)
My theory= block is cracked internally allowing exhaust pressure from a cracked cylinder into the water jacket???
Where else could that kind of pressure build up? How can I check this without pulling the engine? Dye check the cylinders?
Thanks, I been 2 years on this problem, right now it is minus 28 degrees so lotsa time for more research before spring, and no shop to work in... lol
BTW the hull serial number is 001 is this the first Antigua out of the mold??