Last night I put the boat back together. I read on another forum about a guy with a MPI 502 that was having vapor lock problems. He ended up returning his fuel directly back to the tank instead of the filter. He said this does 2 things, it lowers fuel temps, and helps keep aerated fuel from going back into the pump. He said his fuel temps lowered 20 degrees. So I ran my return back to the tank through the vent line temporarily and ran the boat this way. My pump ran way quieter and held constant fuel pressure. I am going to install a 1 1/2" by 1/2" copper T in the main fill line and return the fuel to the tank this way.
I also checked base timing and ohmed out the coil, both checked good. Base timing is 8* BTDC.
I plan on running the boat this weekend at the lake with the gauge installed since I have not done this yet, to verify pressure holds at WOT.
Also you do not need any tools other than a timing light to check base timing. There is a tan /black wire in the 4 wire connector on the back of the distributor. Cut this wire and splice in a water proof connector, I like to get these off of junk GM cars, they are weather pack style connectors. Start the boat and let it warm up to operating temp and unplug this wire. You will notice that the timing stops moving around on the balancer with your timing light. Set base timing and shut the engine down. Plug the wire back in and start the engine, now the ECM will take back over your timing and your base timing is set. This is the same way it is done on GM TBI cars and trucks. I only use solder and heat shrink on all my splices, do not twist wires together, but splice, or use electrical tape on a boat!
I will report back after my trip to the lake this weekend.
