Forward Speed Pro

[Alchemy]

I am eliminating "causes" rapidly with my Atomic 4 issue, but I will solicit the forum for suggestions beyond my idea.

Here's the deal: My direct-drive A4, with an 11 x 8 Gori folder prop, will reverse with full throttle, but will not power forward in gear beyond about one-third, which is too gutless to maneuver into the wind well.

The prop is a little overpitched, I know (the original was a fixed two-blade 12 x 6), but that's not the whole story. We had the shifter assembly apart to reduce slop and to check the cam for wear: it is snug now. We realize that the carb may be involved, but if there was a problem with the high-speed jet, I couldn't get loads of reverse throttle, or so I think. The fuel bowl is clean.

So now I think it's the tranny. I think the set screw on the clutch plates is slipping and that this needs adjustment...a job needed contortions and a couple of mirrors.

I've got the Moyer manual (actually, I have three different ones, plus the Universal owner's manual) and I was a member of the old A4 mailing list for years (RIP "Qshicks"). I've actually rebuilt an A4, but I'm a little stumped by this.

I ran in forward just fine previously to this. I got 6.4 kn top speed with the original 12 x 6 fixed prop and 5.8 kn with the folder, but I can't get 5 knots currently. Usually, I never run the throttle past the "12 o'clock cruise speed" notch...I just burn twice the gas for that last 3/4 of a knot. Anyway, the folder advantages (including better stopping power) are worth the slight speed loss to me, but this is another case entirely.

If I disconnect the throttle linkage and work the throttle with a finger, it's the same deal: only some thrust and then no more. I just wanted opinions here before I go checking the clutch plate set screw, which is awkward stuff.

Do I seem to be on the right track? What else could give me the ability to throttle high in reverse and to get very little acceleration in forward gear (I can also rev high in neutral).

Thanks!

[Trysail]

Sounds similar to my previous problem.

If I understand you correctly, the engine is NOT slipping, or over revving at higher RPM.

Do you have a tach? If so, how many RPM are you getting?
Have you cleaned your prop? Is the bottom horribly dirty?

Check your exhaust. I checked mine first, spent money of parts and a compression gauge, did hours of labor, only to find that I missed a section of exhaust that was blocked.

Here is my a link to my thread. There was a lot of great replies:

http://www.moyermarine.com//forums/s...ead.php?t=4249

[hanleyclifford]

I think that 12x8 prop is more of the story than you think. 2 inches change of pitch is HUGE on an A4.

[Alchemy]

All good suggestions, but not at this point the primary cause, I think. I've regapped the sparks (RJ12Cs) to .35 as they were a little less, re-seated the (new) spark wires and am preparing to check the points, condenser, rotor, etc., as failing points could explain why I can't get revs in forward, and the reduction gear in reverse could explain why I APPEAR to get greater RPM in reverse, but in fact it just stops revving higher at a slightly later point in the throttle lever positioning.

I do not think it is the carb, nor do I think the forward gear collar thingie requires adjustment. The prop might indeed be dirty, but not THAT dirty...last week I was motoring with no problem. Today I got one of the five starts to show some revs in forward (tied off at dock) and that points to an intermittent ignition flaw. Or so I am thinking.

So I will examine and change the points tomorrow, because the block got too hot today to stick my finger over piston 1 to determine TDC. Ow.

[67c&ccorv]

When was he last time you had the Gori folder propeller rebuilt/maintained?

Remember that in reverse - you have a reduction gear advantage with the direct drive transmission over forward gear. A poorly performing engine may achieve full throttle rpm in reverse because of the mechanical advantage..but be unable in forward gear.

BTW - like Hanley says, that change in pitch on a 30hp max motor is a lot!

[Mark S]

Originally Posted by Alchemy

My direct-drive A4, with an 11 x 8 Gori folder prop, will reverse with full throttle, but will not power forward in gear beyond about one-third, which is too gutless to maneuver into the wind well.

How many RPM's are you talking about here?

Mark S

[Alchemy]

Originally Posted by 67c&ccorv

When was he last time you had the Gori folder propeller rebuilt/maintained?

snip

BTW - like Hanley says, that change in pitch on a 30hp max motor is a lot!

I serviced the Gori prop this spring. It's an exceedingly simple device.

Yes, going from a 6 to an 8 pitch is a lot, but this prop came off a C&C 35 Mark I running an identical Atomic 4 engine to mine, which is in a Viking 33, a boat two feet shorter and two tons lighter than the boat from which it came. Also, I've had it for several years now with no problems, unless one considers "stopping faster and a slower 'dead slow'" problems...I called 'em "solutions".

[Alchemy]

Originally Posted by Mark S

How many RPM's are you talking about here?

Mark S

I estimate from engine sound to be 1200-1300 RPM. I don't have a tach installed, alas, but I'm pretty familiar with the engine "notes". I have rarely driven the engine beyond the "cruise notch" at 12 o'clock on the throttle, which gives me about 5.2-5.5 knots at what I estimate is 2,200 RPM.

Idle is about 800-900 RPM or a little fast.

[Mark S]

Does the engine suddenly rev higher with no power past 1300 RPM? Or is it that you can't increase engine speed past 1300 while in forward? If the former, adjust the clutch plate collar. If the latter, don't.

Mark

[Alchemy]

Originally Posted by Mark S

Does the engine suddenly rev higher with no power past 1300 RPM? Or is it that you can't increase engine speed past 1300 while in forward? If the former, adjust the clutch plate collar. If the latter, don't.

Mark

The latter, but that's in the past now. After the application of some time, labour, grey matter and the inevitable money, the problem appears to be solved.

It was the distributor that really needed a tune-up. In consultation with a learned friend, I replaced the cap (the old one had cheap-ass aluminum contacts), the condenser, the points (the old ones were visibly fried) and the rotor, also zapped-looking. I'm surprised the thing ran at all. Repair kits are cheap...$23 plus shipping (http://www.marineengine.com/newparts...Engine=&Model=), so I'm ordering spares and doing this every year along with the impeller.

I ran the engine at dock (sending out 50 feet of turbulent wash), and out in the harbour and thanks to the somewhat oversized pitch, it still doesn't produce the right RPM "note" in forward, but it pushes the boat at 6.1 knots with the 11 inch prop, which compares favourably to the 6.4 I got with 12 x 6 fixed. My understanding is that I can fairly cheaply repitch the Gori down to 6 inches of pitch, at which point I should produce higher RPM "up the power band" and stress the engine less,meaning the blow by I sometimes see will likely go away.

Thanks for all your suggestions. If further problems develop, I will mention them here.