Vibration under power

[steved]

I'm new to this game as a 1st time boat owner and loving my 1977 E32. It has an Atomic 4. The boat has spent it's life on the Great Lakes and is now in Milwaukee.

I have a vibration under power that begins to be noticable at about 1,700 RPM. At 2,000 the vibration is seemingly 4-5X the itensity that it is at 1,700-1,800. The engine in neutral seems smooth all the way up to 3,000 which has me thinking that the issue might be related to the prop or the shaft.

As I very slowly raise the RPMs from 1,800, at about 2,200 the engine quickly races up to 2,600, 2,700, and it's seems like the prop or shaft are just slipping at that point. I immediately back down. This condition seems to be easy to reproduce and is a consistent reaction.

Are the two conditions, the vibration and the seeming slip of the shaft or prop separate issues? How do I begin to sort this out? I'm not mechanical but love putsing and learning new things.

 

[treilley]

Change the tranny fluid, check the shaft alignment and see if that helps. Next replace the engine mounts and realign the shaft.

Your transmission may be bad but I would rule out the cheap and easy stuff first. also, call Don at Moyer Marine. He is a great resource for these great engines.

 

[Rhynie]

Sounds like a slipping trans; there is an adjustment for the fwd band - not hard but have to be a contortionist. The suggestion to contact Moyer Marine is a good one; I believe that there is an online manual available through them.
The A4 trans shares the same oil as the engine, so no separate trans fluid to change. Also, you want to stick with just plain old HD oil as the newer synthetic types are slipperier and can promote trans slippage.

Good luck,
Brian

 

[tenders]

Not all Atomic 4 transmissions have the same oil as the engine. Mine (a '69 E32) has a V-drive which has separate transmission oil.

For your vibration symptoms I would suspect a folding prop that hasn't completely unfolded, or a cutless bearing that needs to be replaced. It could be engine misalignment, but I'd check the more obvious stuff first (even more obvious than treilley's also very viable suggestions) before I started messing with that.

I think you have identified a slightly loose adjustment on the transmission allowing it to slip. That is probably a separate item. But brian makes a good point -- if some well-meaning previous owner used synthetic oil, get it out of there. It's too slippery for A4s.

There are tons of information on this on the forums at moyermarine.com.

 

[Cory B]

Transmission linkage

Also make sure that your transmission linkage goes all the way forwards - you should feel a fair amount of resistance just before it locks in. Its possible its only partially grabbing the cone. If you open up the tranny cover plate you can see if its grabbing properly or not (with the engine off!). As mentioned above Moyer is the guru of all things Atomic4.

The A4 transmission is a good user-serviceable design.

 

[CaptDan]

Are the two conditions, the vibration and the seeming slip of the shaft or prop separate issues? How do I begin to sort this out? I'm not mechanical but love putsing and learning new things.

First and most important thing to check is engine alignment. If the engine mounts are out of adjustment or deteriorated, you run a HIGH risk of snapping the 3/4" diameter shaft. Don't ask me how I know this.

Insert a feeler gauge between the shaft and coupler housing, checking alignment vertically and athwartships. If the spacing isn't equal, the engine must be brought back in 'true.' If the engine mounting bolts and steel beds are deteriorated, preventing adjustment, (a common thing with these good old boats), they must be replaced.

Also, the cutless bearing is a prime vibrational culprit; a diver can check it for you if you're not ready for a haul out. Or - you can arrange a 'noon hang' inspection with a boat yard, a cheaper alternative to an on-the-stands' dry docking.

Second issue is the prop, as has been already mentioned. Any number of things can cause it to induce vibrations: marine growth or damage to the blade(s), malfunctioning folding mechanism, etc. If you have the original
12x9 'egg beater,' you might consider a replacement. There are differing opinions on what a suitable replacement might be.

Third, from what you describe, the transmission IS slipping at higher revs. This is a rather easy thing to adjust, but you DO need the A-4 manual for instructions, and Don Moyer is your source: moyermarine.com

There's also an online A4 forum run by Don; you should join up and post your questions there as well.

Good luck, and enjoy that fine E32.

Capt Dan G>E35II "Kunu"

 

[steved]

Thanks for giving me a list of possible culprits

I appreciate all the suggestions thus far. I should have noted that the boat was hauled out for the season prior to me posting my original question, so I can't check alignment just yet. I've learned it needs to be in the water for that as the hull flexes a bit between with cradle and in the water. I will go over all of the other possibilities while it's up. The prop appears to be in perfect condition without a single nick. The Cutlass is nice and tight. I've secured Don Moyer's A4 manual. I haven't opened the tranny yet. It seems you need to be a contortionist just to get a wrench within a foot of any of the bolts!!

 

[steved]

Thanks to all

I finally got at working through an alignment. It was quite a ways out. That helped a great deal. I was also able to contact Don and he gave me the proceedure to tighten the adjusting collar. So, no more slippage and vibration seems to be 1/4 of what was. Thanks all.