Thanks for the reply's and questions. I'll start out by letting you know I just purchased the boat. It hadn't been run since 1999. Apparently the previous owner passed away, and his kids never got to take her out. From my interpretation of the records this boat had to have been in tip top shape when it was last run. The previous owner was a Retired Coast Guard Officer and Current Coast Guard Auxillary member. You wouldn't believe the documentation and logs that were kept. The safety stuff on the boat and prelaunch check sheets for every trip traveled suggest this girl was in perfect running condition all the time or it didn't leave port. Therefore, I can only assume the boat has been well taken care of and should be a simple little thing to fix.
Now to let you know a little about me and my diagnosis. I am not close to a mechanic, but I always find myself fixing engines out of necessity and the joy of figuring it out. Most of my fixes come from learning about the problem asking questions of mechanics, going to a parts store, ordering the part, then I search the engine until I see the look alike and replace it. I'm getting to the point where I know a little more than that, but in reality it's not much more than that.
So when I bought the boat I had a top notch marine mechanic get it running with no limit on funds to make sure it was perfect. The problem is it runs perfect in the garage, but once in the water it dies. The other engine runs perfect. He lives in Texas, I live in Idaho so taking it back isn't an option. This is what he did; he drained the fuel, changed the fuel filter, fresh water impellar, oil, fuel pump, 2 new batteries, rebuilt the carb, compression tested, timed, new cap and rotor, spark plug wires, and put in 50 gallons of super unleaded.
I got the boat delivered, and took my family out to dinner that night. The boat ran perfect for about 5 miles, we docked, ate dinner and headed home. I dropped my family off at our beach and when I went to put her away she missed a little (first indication something was wrong sludge in the fuel was my guess, took 10 miles to build up). Temp was about 175 (guage has marks 160 - 200) so can't be exact, but figure anything in the 160 - 200 range is good enough to keep it running. Oil pressure was about 80, fuel guage didn't read, but got her tied up and thought sludge in the fuel.
Took her out the next day and ran her hard (3,500 - 4,200 rpm) for about 15 minutes then it missed and died. I couldn't get it started again so had to limp home. All guages read good except for the fuel.
The next morning I drained the fuel tank and at first thought it had to be the fuel because of what appeared to be a lot of sludge, but the second 5 gallons came out clean and 40 gallons later I felt perhaps it wasn't the fuel. I put the fuel into my truck (including the first 5 gallons) and never had an issue. I replaced the fuel filter, spark plugs, alternator, replaced the fuel float and sender unit (extremely gunked), and repaired a wire to the regulator that had broken off. I also noticed a port coming out of the bottom of the carb that if I put my finger over it when it was running it picked up a little meaning it was sucking air straight into the carb so I closed this port off. Found out this was a vaccum port that should have been closed off.
I then thought for sure I had it dialed in asked my wife to jump aboard and we'd run over to the nearest marina and have some coffee (she's definately not too excited about another boat especially one that doesn't work). We got out 10 minutes I heard a miss so I backed her off to just idle speed and we cruised into the marina with no problem. Perhaps I've learned a little about when I'm with the wife getting there is a lot better than trying to hot rod it and end up paddling home.
I conned a buddy to head out with me for the next test run, and 15 minutes into it it missed, sputtered, back fired and died. All guages looked good. We pulled the hatch and water was everywhere. Thought I had a bad hose, but couldn't get the engine started again or feel anything unusual. We pumped the gas a couple of times, and sure enough we were getting fuel into the carb. Paul mentioned this might eliminate some things from the fuel side, is this right? I'm going to double check it, because when we were looking at this our intent was to start the engine not diagnose so looked at lots of things and didn't write them down or finalize that was the problem. Perhaps I pumped fuel at a later date when I was trying to diagnose and that is what I remember.
The next morning drained the gas again and then started her right up, and found the main engine water pump was seized. In my mind this had to be it. If you can understand why I thought this was it you can understand exactly how the boat performes before it dies. I thought when the thermostat would open at temperature it caused water to spray directly across the rotor, and what water escaped from there went straight into the carb causing missing, backfiring, dieing, and a too hot of engine that wouldn't let me restart it until it cooled off. Change the water pump and I can get my wife back out there is what I thought
I called my Texas mechanic and he recommended his most trusted source for a pump guy in Florida. He agreed without a doubt this was the problem. I called the guy in Florida and he convinced me if I was exclusive to fresh water to use an automotive pump as long as the rotation was correct. I would have to fabricate it so the closed thermostat water could cycle back into the fresh water pump. This was accomplished by pulling the old pump, and seeing what he was talking about. I had to tap a 1/2 pipe into the pump and conect the hose to this point. Exactly like the original. This allows the cold water from the fresh water pump to be diverted into a hose on a closed thermostat, back into the water pump and out the manifolds. Simplified somewhat, but that's the set up.
Not sure I liked putting the automotive pump on, but the guy in Florida builds marine pumps and assured me it was the same. I reinstalled it, took it out for a test drive, 15 minutes into it a repeat of how it died. However, the pump seemed to be working as it wasn't spraying water everywhere and the temp guage was 175.
Next talk was to a local marine mechanic who is swamped so didn't want to look at her, but before I could get the words out he said you have a bad coil. It takes that long for them to heat up and it would be his first place to go. I didn't tell him anything about all the previous stuff I had done so this was his first thought. He also said go to the autostore and get a coil it would be a cheap test. I also talked with a diesel mechanic about an automotive coil vs marine. He said it doesn't matter, but swore it had to be heat/water related. Change the thermostat. So I changed both.
Took her out again. 15 minutes into it she smelled hot and the temp guage read 200 - 210. I shut it down and limped back. At the dock I wanted to look to see if I had a thermostat housing leak, but couldn't get it started. Took the old thermostat and put it into hot water and sure enough it works okay. I'm planning on putting it back in because the replacement stat didn't look the same.
So for a rundown of the engine. I don't know for sure what's original and new. I know the fuel pump is a factory rebuilt marine pump, the coil and water pump are new, but automotive. The manifolds look stock and if anything perhaps the carb is an after thought. It's a Holley, and I've had other CC's and they have all been Carter's. It is hard piped to the fuel pump. The plug wires are some sort of racing set that I have a difficult time knowing if they are seated or not. I do not know about the the PCV valves and ballast resistors that Paul mentioned other than they are there. I've heard about the PERTRONIX system, but don't know the ins and outs of changing over or if it's worth it? I question timing. Some say it's not timed correctly, but my understanding is if it's not timed correctly then wouldn't the first 15 minutes also be missing? I read that 7 and 8 wires shouldn't be touching?
It is a fresh water cooling system and I like the thought of a bad choke. I was talking to the buddy I conned into going out with me and he wondered as an after thought being a Holley it's actually an electric choke. He wondered if it could be cross wired? At start up it's wide open, so could that mean when it heats up it actually closes? I haven't thought to look at it after it shuts down. We did when we tested to see if gas was getting into the carb, but can't remember if it was open or closed. We had our fingers, screwdrivers and pliers prodding all over the thing. Our intent was to get it going instead of understanding so didn't pay close enough attention. Because it starts right up when it's cold I'm contemplating disconnecting the wires anyway.
Hopefully this gives a pretty good description of what I know. Obviously a lot of words with a little detail, but because I don't know the correct lingo about diagnosing I'm describing the symptoms the best I can to hopefully spark some thoughts about what it could be. Any and all suggestions will be followed up on, until I get her perfect.