Hello all,
I’m not sure if this is the right place for this question so if not, admin please point me to the right forum and I apologize in advance.
I’ve got a stock 250 crossflow in my (older) jet boat and would like a bit more power. The engine is from an 85 falcon I think, and has a C2 head and Weber carb. It tops out at 3950 rpm which I am guessing is around 130hp on my impellers (2 stage HamiltonJet 752 with 19 degree bullet front and 17 degree rear). I really want a bit more zip, and would like to get to 4350 rpm, or even 4500. That would require 177hp or 195 hp respectively ( jet power is proportional to the cube of the engine speed). So I need a high torque engine. The engine will never see 5000 rpm - that’s almost 270hp on my pump.
Is this economically viable ( I’d like to keep to around $2k in parts)?
Can I get there with a cam swap, and sundry parts? Do I need a new inlet manifold, and if so, should I go to a 4 barrel carby (450 Holley or similar)? One key restriction is I am keeping my log style water cooled exhaust manifold, so extractors are not an option.
My other plan is to drop in an used AU or XR6 engine as I can pick one of them up for about $1000nzd here in the South Island of NZ and reuse the exhaust manifold but I’m not too keen on playing with or remapping ECU to be honest, or messing with drive by wire conversion on the electronic engine. But I know it can be done, and the XR6 is a good engine, but that’s not my desired path. I’d prefer to warm up the crossie as it is a good, relatively light engine.
I’ll add some pictures tomorrow when I figure out how to post them. Thanks in advance for any ideas or feedback.
regards Rich
