Engine Tech - More Horsepower for a Bridgeport?

Jay,

I purchased a used boat with a pair of 2.4 Bridgeport carb engines. The motors seem to be in excellent shape. What kind of mods can be done on these to give me some additional ponies?

Fred

I received the photo of your Skater; looks like with that many people in it it's smokin!

The first thing I would do is get the motors warm and do a compression test with a good gauge. Take all the plugs out and with a good hot battery, spin the motors over with the throttle bores wide open. When the pressure has reached its top number, write the amount of each cylinder tested down. With the size and weight of your hull I would guess that you would be safe on pump gas with 145 to 148 lb. of compression at stock ignition timing. If your compression readings are any lower than the above numbers, I would take the heads off and send the heads along with one of the head gaskets and the tally of the compression tests to a competent shop. This should give the machinist enough information where he can make a educated assessment with the three things you have furnished; one, the compression numbers, two, the head gasket thickness, and three, the head so that he can CC them and determine how many CC ' s to diminish your heads to bring you up to the maximum pump gas compression and thus, maximum performance.

Next, I would check and see how the reeds are sealing. This is done by removing the carburetor and intake manifold, then inspecting the reed plate with the reeds attached. I usually hold the reed assemblies up to a light and if I can see cracks of light through them. This is the same as an intake valve leaking on your family car - it will not idle smooth and will suffer in the transition in moving up the rpm range under acceleration. At this time, a quick check of the timing and a fresh set of plugs are in order. This works wonders on a set that has been used a season.

This is a pet peeve of mine also, and I know everybody gets tired of hearing me talk about it: if you are not using a good grade of synthetic oil make an effort to change over to this type of oil in the motors and your gearcases. Your motor will live longer with less likelihood of loading up and misfiring due to the burn nature of the petroleum oils.

Another good idea is to check the bottom of your boat to make sure there is no marine life build up on the running surfaces. Also remember, sharp edges of the bottom leaving the transom are "faster" than round edges. A little secret also, space your props as far back on the shafts as possible with spacers and have a nut machined in half, and torque to 100 ft lb. Leave the prop shaft just long enough to have one thread of the prop shaft hanging past the nylon on the lock nut. Believe it or not, this simple mod is sometimes good for as much as 4 mph.

I hope I have answered your question without going deep into the motor and your pocket book!

Thanks for asking JSRE

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