First, a preface: I am not an airboat builder. I purchased a 4A084 engine for another purpose but this seems to be the remaining active online repository for 4A084 engine. I figured if I shared my project with you all it might help someone out. So, on to the project.

Recently I purchased a Hercules 4A084-3 in an unknown condition for a song. I was finally able to get it running yesterday and after I plumbed up a makeshift muffler to get a listen for mechanical noise I discovered the engine is nearly silent mechanically. Compression is 130 across all 4 cylinders and although the Tillotson carb is dealing me fits, the engine purrs like a kitten when the mixture is right. Probably has something to do with the float needle seat being as hard as a rock and won't seal. That MIGHT explain the carbon buildup on the freshly-cleaned spark plugs. Anyway, I digress.

The points are in bad shape. I mean very, very bad shape. Coming from a small engine repair background I have come to loathe points-condenser-magneto ignition systems (Especially the ones behind the aluminum flywheel seized onto the steel crankshaft) and since the points are already needing to be replaced, what better time to convert to something a bit more modern? My plan is to initially retrofit the engine with different plugs and a COP ignition system being run by a microcontroller. The COP should help mitigate EMI vs plug wires and remote coil packs. Phase 2 is to add port fuel injection. Here's the plan for parts on Phase 1:

Coils: Toyota 1ZZ's, p/n 90919-02239 $40/4 at the junkyard
Controller: Speeduino v3 - $100 (Self-asssembled, I already have a couple Arduino Megas laying around collecting dust)
Plus wiring connectors and misc odds and ends that usually end up doubling the cost

I will have to make a trigger wheel for the crank and I'm not entirely sure how I want to go about it. Since the front of the crankshaft is not keyed on my engine and if for some reason the pulley is removed the trigger wheel-piston timing will be changed requiring a whole bunch of work to re-time it all again. No bueno. So that leaves two options. Either placing a trigger wheel on the back end, OR machining a plate that bolts in place of the magneto and sliding a shaft through a pair of bearings, slipping on the magneto gear, and having that drive a 36-1 trigger wheel right where the magneto currently sits. Since there will be slight variations due to geartrain slop I am not 100% sold on this idea, either. Or I could put the wheel on, tighten the nut, and pray to God I never have to remove it and re-time it again.

Right now I am still in the cleanup and gasket replacement stage. She holds oil well enough but I would rather do it now while parts are still readily available vs 10 years from now when gaskets and seals are having to be heisted from a museum somewhere. Thoughts on how insane I am for going this route?

Future plans for EFI should be somewhat straightforward. Welding injector bungs into the existing intake tubes, adding a fuel pump and regulator, fabbing a fuel rail, and using the existing carb as a throttle body if I don't buy an el-cheapo 34mm throttle body to replace the near-worthless carb. Oh, and an O2 sensor. Can't forget that. Maybe put in 3 or 4 upstream and downstream of a catalytic converter to make the granola-munchers happy.