Limited RPMs

[djmorris]

I'm buying a 1975 C&C 30 with an Atomic 4 and about 5 days, 2 Great Lakes, and one major canal between her and home. The surveyor discovered she'd produce no horsepower in forward. This was traced to a now-replaced bolt in the clutch. The engine starts up easily and runs smoothly, but seems to produce only enough revs to get up to about 4 kts in calm conditions (there's no tach). Only the bottom one-fifth of the travel in the throttle control arm has any effect on the engine. The current owner says there's no issue with the control linkage. During the sea trial, he pulled the lead off cylinder 1, which stalled the engine. He suggested this indicated the cylinder was firing properly (otherwise the engine would run), but I notice elsewhere in the forum the A4s can run on two cylinders. Any thoughts on the seemingly limited revs/kts and/or the engine needing all cylinders, seemingly, to keep runnin would be much appreciated.

[ndutton]

Points to ponder

1. Good test on #1 cylinder, now how about #'s 2, 3 & 4?
2. Current owner says . . . don't care what the current owner says, let's make sure ourselves. The throttle linkage needs to be checked, especially the outer sheath security.
3. Do we know what size prop is installed, diameter and pitch? Direct drive or reduction gear?
4. Check the centrifugal advance flyweights for smooth operation to their stops. They are found under the points plate inside the distributor.

[thatch]

This is a classic description of how an A4 would die if plug wires 2&3 were crossed. In that configuration you'ld be trying to run your engine on 1 cylinder. Firing order should be 1 2 4 3.
Tom

[djmorris]

1. Good test on #1 cylinder, now how about #'s 2, 3 & 4?
2. Current owner says . . . don't care what the current owner says, let's make sure ourselves. The throttle linkage needs to be checked, especially the outer sheath security.
3. Do we know what size prop is installed, diameter and pitch? Direct drive or reduction gear?
4. Check the centrifugal advance flyweights for smooth operation to their stops. They are found under the points plate inside the distributor.

Many thanks for the suggestions, Neil. The prop is a Gori folding prop. Drive type is direct drive. The owner says the engine stalls out on any one of the leads being removed. I should note that I'm entirely comfortable with rebuilding the engine...in fact, given its age and the fact that the boat is stellar in every other way, I'll likely rebuild it over the winter. So, our buying decision and the price wouldn't differ, my anxiety is around getting it from Port Dover to Kingston.

[djmorris]

This is a classic description of how an A4 would die if plug wires 2&3 were crossed. In that configuration you'ld be trying to run your engine on 1 cylinder. Firing order should be 1 2 4 3.
Tom

Thanks, Tom. This is an intriguing possibility and so easy to confirm. We take possession of the boat on Saturday. At this point, I figure my first checks will be whether or not I can increase the revs at the carb by bypassing the linkage and whether the leads from the distributor "support" the firing order.

[GregH]

Welcome to Kingston!

[tenders]

I was in Kingston last weekend and received the worst haircut of my life in Gananoque. (About every ten years I get a bad haircut on a vacation and complain about it for the next eight years.) I’ve also been to Port Dover and through the Welland...but not lately.

Your symptoms are also reminiscent of a fouled prop (seems unlikely in Lake Erie), or a restricted exhaust. I agree it is weird to demonstrate the removal of plug 1, experience a stall, and not do the same for the other plugs. (My engine just slows down when you do that.) Other possibilities include a dirty or cracked cap, a worn rotor, bad plugs, or very bad plug wires.

[ndutton]

Many thanks for the suggestions, Neil. The prop is a Gori folding prop. Drive type is direct drive. The owner says the engine stalls out on any one of the leads being removed. I should note that I'm entirely comfortable with rebuilding the engine...in fact, given its age and the fact that the boat is stellar in every other way, I'll likely rebuild it over the winter. So, our buying decision and the price wouldn't differ, my anxiety is around getting it from Port Dover to Kingston.

The Gori comes in a variety of diameters and pitches so that question remains. From what I can gather, the available diameters and pitches are quite aggressive for a direct drive Atomic 4 which could explain the entire issue right there or at least be a significant contributor to it.

As for rebuilding, I'd suggest a barrage of tests before going there.