30+ Driveline Questions

[bigd14]

Looking at a 30+ with rebuilt M18 universal and Campbell Sailor 3 blade prop. With transmission in gear at low idle there is an extreme vibration. Not nearly as bad at idle with transmission disengaged. I don't have much to judge it against but it seems really rough. Mechanic said transmission functioned well and this vibration seems normal at the dock but this was underway and seemed worse. The vibration smooths out at higher RPM and she cruises very smoothly at about 2000rpm. Could not get above about 2500rpm. No smoke at full throttle. Thoughts on why the vibration- Motor mounts? Alignment? Shaft bent or whip? Prop not fitting well or not balanced? Any/all of the above? Also what about the top end rpm's. Prop seems right for boat and engine according to surveyor. Oh and shaft was pretty well centered in log and cutless bearing was good and in alignment. And bottom and prop clean.

Thanks

 

[PDX]

I've been on friends' boats, with 2 cylinder diesel engines, that shook and sounded terrible. But they ran and ran. That the vibration smoothed out at higher rpm would seem to rule out any bent shaft/alignment issues.

Worrisome to me would be the fact that the engine wouldn't reach top rpm. Worse case, could be a poorly done rebuild. Or could be the surveyor's assurance that the prop and pitch are correct may be true for ideal motoring conditions with a barebones boat. The M18 is only 14 HP which isn't much for a 30 foot boat with a fair amount of wetted surface (lots of beam and waterline). Was the boat loaded up with full tanks, generous battery banks, lots of gear?

 

[bigd14]

Hi PDX.The boat had 3 adults, 2 6v golf cart batteries and one group27, a full (small) holding tank, probably half full or less water tank and very little gear. In other words, pretty average. And the conditions were about 8kts of wind on the beam and no chop. This is the originally spec'c motor for this model so should be reasonably able to achieve full rpm one would think. I suppose it could have been fuel or air starved a bit but was not able to check that specifically. Diesel mechanic went through it pretty thoroughly and felt it was pretty sound but he was only able to get 2000rpm at dock. He said that is about what he would expect. He did not go on the sea trial. If the prop is correct and clean, hull clean, the engine is reasonably sized for the boat, and its getting enough air and fuel, what would other causes be?

 

[woolamaloo]

bigd,

I have the 30+ with the M18. I have no such low rpm vibration while in gear or otherwise. The Universal Service Manual suggests that the M18 has a max rpm of 3200 with a cruising rpm range of 2100-2600. I have a year old tach that was calibrated after installation. I've had my warm engine to right around 3000 rpm (for a few seconds) and I generally cruise around 2400. But, there is no severe vibration change like you described at any rpm.

I don't know the model of my prop - but here it is.

Good luck.

 

[bigd14]

OK, thanks Jim. Something is clearly afoot. Sounds like some uncomfortable work ahead if this deal goes through. How have people found engine access in the 30+? Mechanic said it was one of the worst he had seen and he was considerably smaller and more flexible than I am...

EDIT: I just realized that the motor is driving a 90amp alternator. The batteries were on the shorepower charger so probably not pulling a lot of juice under way, but nevertheless, could this explain the inability to reach max (or close) rpm?

 

[woolamaloo]

Checking the oil and getting to the water pump are great. I have a hose going from the oil pan drain to starboard of the engine so pumping out the oil for changes is great. (It's a little bigger hose than the dipstick tube.) Belt adjustment is pretty straight forward. The rest of the engine access is fairly brutal. One of the first things I do when doing any maintenance on the port side of the engine is disconnect the galley sink drain. With the sink drain removed, getting the oil filter off is pretty easy. Also, getting to the water intake to winterize (maybe not a problem for you) is also easy with the drain removed. My Racor fuel filter causes me particular problems because it's up high on the starboard side behind and mostly hidden by a bulkhead and hard to see with my bifocals. Adding coolant is ridiculous. I use a really long funnel at a really shallow angle. And NOW the hard part. To get to the rest of the engine, you have to crawl into the port lazarette. Once origamied in there, I can check the transmission level and change the heat exchanger zinc. The hardest thing so far is changing the fuel filter on the starboard side of the engine while sitting in the port lazarette. You can't even see it from where you're sitting.

I know that I will never change the heat exchanger or muffler myself. I'm just not limber enough to do the job. When the time comes, those are both checkbook jobs for me.

 

[Frank Langer]

Jim,
If you have the 5416 16 hp diesel engine, try changing the fuel filter from the front of the engine just leaning over the engine, catching the filter and any fuel in a large size yogurt container. It's much easier than from in the locker. A piece of cake!
I don't know if it's the same on the M18 engine.
Frank
Frank

 

[TakeFive]

M18 should be able to reach max rpm (3200) at idle and cruise at 2600 rpm.
If you're not hitting 2600 the prop is oversized in either pitch or dia or both.

No engine should vibrate. Check the obvious suspects such as alignment, motor mounts, firing on one cylinder at low speed.
Exhaust smoke at low speed might indicate misfiring. Might be a good idea to have an M18 mechanic look at it. Either that or buy a SeaTow membership.

 

[bigd14]

Thanks for all the responses. I'll cogitate over this for awhile and see how I feel about it tomorrow.

In terms of access, it looks like one could cut a larger opening and put a larger door or pair of doors on the bulkhead below the sink and free up some access space there. And on the boat I am considering, removing an extra battery from the port lazarette and removing the hot water heater from the top of the fuel tank might allow one a bit more room in there.

 

[bigd14]

Just to follow up on this, the original RPM's were measured at the motor, but were not converted properly to what the tachometer was reading, so my tach readings during sea trials were not accurate. Upon further testing the motor was actually running at appropriate RPM. That only leaves the vibration issue.

 

[Alan Gomes]

Looking at a 30+ with rebuilt M18 universal and Campbell Sailor 3 blade prop. With transmission in gear at low idle there is an extreme vibration. Not nearly as bad at idle with transmission disengaged. I don't have much to judge it against but it seems really rough. Mechanic said transmission functioned well and this vibration seems normal at the dock but this was underway and seemed worse. The vibration smooths out at higher RPM and she cruises very smoothly at about 2000rpm. Could not get above about 2500rpm. No smoke at full throttle. Thoughts on why the vibration- Motor mounts? Alignment? Shaft bent or whip? Prop not fitting well or not balanced? Any/all of the above? Also what about the top end rpm's. Prop seems right for boat and engine according to surveyor. Oh and shaft was pretty well centered in log and cutless bearing was good and in alignment. And bottom and prop clean.

Thanks

At what rpm is it idling while in gear with the shaking? I'm speaking of the actual number (e.g., as measured by an optical tach) and not what the tachometer on the engine panel says, which could be off a fair bit.

 

[PDX]

A propeller problem can explain vibration at low speed that disappears at higher speed. Loren had a situation a couple years ago. Changed from a two blade to a three blade prop. And then was not happy with the vibration at low engine speed underway. Vibration smoothed out at cruising rpm. Turned out the three blade prop (new) had one blade with slightly different pitch than the others.

I don't know how common it is for mass produced propellers to have this kind of manufacturing flaw. But if there is something wrong with the propeller it would be an easier fix than trying to trouble shoot engine mounts, coupling alignment, cutless bearing, etc.

 

[Alan Gomes]

A propeller problem can explain vibration at low speed that disappears at higher speed. Loren had a situation a couple years ago. Changed from a two blade to a three blade prop. And then was not happy with the vibration at low engine speed underway. Vibration smoothed out at cruising rpm. Turned out the three blade prop (new) had one blade with slightly different pitch than the others.

I don't know how common it is for mass produced propellers to have this kind of manufacturing flaw. But if there is something wrong with the propeller it would be an easier fix than trying to trouble shoot engine mounts, coupling alignment, cutless bearing, etc.

Campbell Sailer props are not mass produced but are custom made to order--which, of course, does not preclude the possibility of a flaw. They do seem to be a very high quality product. I switched to one earlier this year and spent a fair amount of time talking over the exact specs for my (under powered) Yanmar 1GM. I've found these folks very responsive and I'm sure they would be able to assist with any troubleshooting of the prop. I would e-mail Kelsey@westbynorth and see what he has to say.

 

[Christian Williams]

Most of our diesels vibrate like crazy at some rpm. If by a small change in rpm the vibration reduces to acceptable, that's normal small diesel stuff.

It is apparently not as noticeable on a tractor.

 

[bigd14]

I am pretty sure the worst shaking was at low idle, which should have been about 800-900 rpm. I will get to work on the vibration issue... sometime. Much to do still to get this boat in hand. The purchase price is finally agreed upon, now just have to go through all the process. I'll report back when its all said and done.

Thanks for all the responses. Makes me feel pretty good about the overall health of the motor, minor maintenance issues aside.

 

[Frank Langer]

Congratulations on getting to this point, and good luck finalizing the purchase!

Regarding the vibration, it does vary according to the RPMs. On our E30+, I notice it worst at a speed of about 4 knots, less at initial idle and at about 5.8 knots, but then a bit more above 6 knots. I have learned to find the speed at which it is most comfortable. But it's still a good idea to do an alignment and check the drive shaft when you have time.

But also take some time to sail, so you enjoy your boat, rather than spending all your time on maintenance projects--on an older boat there is no end to those, even on a lovely Ericson!

Frank