175hp omc v8 302 over heated at high speed only

[arield]

Need your help, Testing a 77 OMC 175hp v8 ford motor/ Stringer outdrive. . took around the lake to test for the first time, at moderate speed, it is running fine, felt fine. So far so good, so we need to find out how fast it would run. , but once we hit the throttle at high speed 4000rpm or higher the boat sounded it backfired, and felt like it was choking,

 

[wire2]

Re: 175hp omc v8 302 over heated at high speed only

After a run, are the risers too hot to put your hand on? if normal, impeller is probably ok. I'm inclined towards a blockage in the exhaust. Does your temp gauge say overheated?

 

[arield]

Re: 175hp omc v8 302 over heated at high speed only

guage had no sign of overheating. took the boat to the shop because we were clueless, the shop thinks it a distributor problem? shop diag- no sign of overheating, but the popping sound was backfiring. shop diag that the the owner did some modified and put in the wrong distributor (car).