9.5 Sportwin Power Loss

I have a '67 9.5, when first purchased motor it ran great and planed my 14' aluminum jon easily. Started having "power" issues so... I rebuilt the carb, installed a new fuel pump, new fuel tank, fuel lines from connector to pump and from pump to carb, tank line, filter on tank plus new lower unit with water pump housing and associated parts, also tuned with resetting of existing points and new plugs. Also replaced the prop hub and even tried a different pitch and diameter prop with no luck. The motor starts easily, idles like a sewing machine and trolls like a champ. However, when powering up it takes a long time to reach what speed it can produce. Also, since all of this, I seem to have lost power as the boat can barely plane. It seems as if the motor wants to go more but just cannot get there. Am I missing the obvious here?? I am starting to believe the "if it ain't broke don't fix it mantra". Any and all suggestions would be appreciated. Forgot to mention, compression (65, 70) and spark is good on both cylinders.

Re: 9.5 Sportwin Power Loss

That compression isn't the greatest. Does it increase if you crank the engine via a rope around the flywheel?

You say good spark. With the spark plugs remopved, that spark (on both cylinders) should jump a 1/4" gap with a strong blue lightning like flame..... a real SNAP! Does it?

S/Plugs should be Champion J6C plugs, gapped at .030. Possibly you inadvertently set the points incorrectly? It happens, see the following.

(Point Setting Of Magneto Models)
(J. Reeves)

Set the points as follows. Have the flywheel key aligned with the fiber rubber portion of the ignition points. Adjust the gap so that a .020 gauge will pass thru but a .022 will not. Should there be any question of the points being dirty (touching the contact with your finger would cause them to be dirty), clean them with a small brush and acetone or lacquer thinner.

NOTE: Should the operating cam have a small portion on it with the word "SET" imprinted, align this portion with the fiber rubbing portion instead of the flywheel key.

Re: 9.5 Sportwin Power Loss

I agree about the compression, however, it ran great with that same compression before. Never tried a rope around the flywheel, will see what new that brings. Spark is good and plugs are gapped properly as well as the points. Would a decarb help?