Would this be blasphemous?

Wow, thats a lot of good info from you guys out there. Thanks. I'm a bit of a purist myself, so my first instinct is to try to keep the boat as original as possible. I was really just curious as to the feasibility of a modern powerplant upgrade. I spent 2 years restoring a '74 Harley Ironhead that I love riding and that always needs a little tinkering, too. Like I mentioned before, I think that I'll take this winter to go through anything I haven't touched yet, and touch on the things I already have, and see where we are in the spring. Thanks again for all the feedback.

The nice thing about re-power is three years from now every known part on the package will be available. I have a customer here in town we did a 79 SN with an Excalibur and zero off.. The guy runs it salt water too!!Skis great as it is stripped down to nothing more than two seats and motor box,

It sounds like a vacuum leak. Someone needs to bust out a gauge and start doing some testing. If you aren't capable you need to find someone locally who is well versed in carburetor engine diagnostics (doesn't matter if it's a boat or car guy). That is getting fairly hard to find these days but most marina guys are just as bad at EFI as they are at Carbs so it doesn't really matter either way.

If you are up for a little project this winter and want to add some jewelry to your tool box there are plenty of guys (already commenting in your thread) that can walk you through the diagnostics of your system if you are even mechanical in the slightest.

I didn't buy it new, but I managed to get an EFI engine for my old Supra to replace the old 351. However, the old engine went into a boat now owned by my father-in-law, and he's been using it for 11 years, so I can offer you a direct comparison.

The EFI engine sounded the same if not better, going through the same exhaust; it was also a 351 but just a more powerful variant (the GT-40). It started every time but takes more revolutions to fire. It ran perfectly in spring, fall, hot summer days, and everything in between. This was nice because I used the boat well into the cold months. I also appreciated the extra power, (310 vs 240) because it was a big, heavy 21' boat. With regular tune-ups, the boat ran perfectly for 11 years. DISCLAIMER: I believe I got a deal on the engine because it had been overheated at some point. It had a knock at cold startup that would get better when warm. Eventually I tore it down and had a machine shop rebuild it - bored out the cylinders .020, put in new pistons, rings, connecting rods, bearings, that kind of stuff. Never did it let me down, but I should mention that rebuild haha.

The old carbureted engine in that same time period has also run perfectly with regular tune-ups. It's had a fuel leak that was easily solved, it needed a new thermostat last year, and we've replaced the cheesy EI conversion kit in the distributor once, because the old one was literally held together with scotch tape (long story). It needs an extra pump of the throttle at cold start, and otherwise is basically a bump of the key to get going again once it's warm. I had a '72 Ford pickup with a 302 that was literally the lightest touch of the key, it was so satisfying to start that thing. This engine is close to that, but not quite.

With the help of the knowledgeable people here, you should be able to get your old engine running perfectly. Maybe it's old enough (in terms of hours) that it needs a good bit of attention more than a tune-up, but that's still far less money than a new engine. Maybe a rebuild with a new electronic distributor? I don't think that would bother too many purists. Points are great, I have them in my truck. But they do require more tinkering.

An EFI crate motor would be a sweet upgrade, but you also have to look at whether it would require rebuilding your doghouse / engine cover. In the Supra it was a split cover, so I was able to just rebuild the bottom half to be 4" taller.

I would rebuild when the time comes. KISS Theory

They are going to sound the same and you can always put the original engine back in it. There would not be a market for aftermarket FI systems if people wern't putting them in their 67 Mustangs. Have you ever thought where you would get a FI engine? A used take out or new? What is your budget ?

Bunch of naysayers. You looking to get a brand new engine? Who is going to do the engine install? What would be the budget?

Maybe fix the problem(s)?

Plenty of reliable 70s boats on here.

At the Buckethead race this year a handful of boats were re powered with modern EFI engines and several did not run right.

It is your boat.