I am a new boat owner, have been around boats for years, and am a gearhead. I recently took possession of an '88 Century 20' CC with a 5.7 Merc I/O w/alum GLM exh manifolds. The prev. owner told me he had burnt up the impeller by running without water for a few seconds and had replaced it. I bought the boat with a known carb problem, which upon rebuild, seems to have taken care of that.
I have had the boat in the water twice, and running on earmuffs maybe five or six times. The first few times on earmuffs just to test the carb rebuild. The 350 never got over 140 degrees in the driveway nor while idling around, nor running mid throttle. I returned from my second outing placed the earmuffs on the outdrive and began to flush the motor. (I live in Southeast GA, and run in somewhat sandy/salty waters. I was always taught to flush and drain regardless of where I put in.) I ran the engine approx. 4 minutes to flush with earmuffs, and it began to overheat... I immediately shut it down, concerned that the impeller may be bad again or something. I then checked the oil... good. I then pulled the flash arrestor off to check the carb for sand in the filter and found milky oil in the valve cover vents... this lead me to find water in the #5, #7, and #8 cylinders. I found this by pulling all the plugs and placing cardboard on each side of the motor so that I could see which cyls were spitting out water. There were no tell tale signs on the plugs.
So... I pulled the heads, had them reworked, resurfaced, and revalved(all the valves were shot!), and am in the process of putting it all back together.
In order to not have a repeat performance... do you have any suggestions on other pieces to check?
I also was inspecting the exh manifolds and risers this evening for reassembly, and found about a cup and a half of sand in each one... some of the sand was dark, like it was burnt... Any suggestions?
Thanks in advance...
I have had the boat in the water twice, and running on earmuffs maybe five or six times. The first few times on earmuffs just to test the carb rebuild. The 350 never got over 140 degrees in the driveway nor while idling around, nor running mid throttle. I returned from my second outing placed the earmuffs on the outdrive and began to flush the motor. (I live in Southeast GA, and run in somewhat sandy/salty waters. I was always taught to flush and drain regardless of where I put in.) I ran the engine approx. 4 minutes to flush with earmuffs, and it began to overheat... I immediately shut it down, concerned that the impeller may be bad again or something. I then checked the oil... good. I then pulled the flash arrestor off to check the carb for sand in the filter and found milky oil in the valve cover vents... this lead me to find water in the #5, #7, and #8 cylinders. I found this by pulling all the plugs and placing cardboard on each side of the motor so that I could see which cyls were spitting out water. There were no tell tale signs on the plugs.
So... I pulled the heads, had them reworked, resurfaced, and revalved(all the valves were shot!), and am in the process of putting it all back together.
In order to not have a repeat performance... do you have any suggestions on other pieces to check?
I also was inspecting the exh manifolds and risers this evening for reassembly, and found about a cup and a half of sand in each one... some of the sand was dark, like it was burnt... Any suggestions?
Thanks in advance...