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Old 27-05-2020, 06:08   #1
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Maxprop Cutlass bearing Low RPMs

I have a problem with the cutlass bearing on my 2000 Beneteau 461. When hauled the surveyor noticed the cutlass bearing coming out about 1 inch. When I looked at it I found one of the little (really LITTLE) set screws missing. I was able to push the cutlass bearing back in with my fingers! Question: The plastic tube holding the cutlass is very thin. There is just no good way to put a serious set screw in. Unfortunately the yard reamed out the holes to fit a thicker screw but no I am SOL.
I would have put in the old little screws and put a SS hose clamp around it. We did put a donut shaped zinc on the shaft between the cutlass bearing and the Maxprop.
2.Problem The yard took the Maxprop off unnecessarily to get to the cutlass bearing. They had a hard time configuring the correct setting when assembling it. It looks ok to me but I don't know anything about Maxprop settings. I learned a lot fast.
The boat runs ok about 7knots at ~2400 rpm. But the tachometer never goes above 1400 rpm. What gives ?? I changed both fuel filters. When NOT under load (prop-transmission not engaged) it reeves up to 3500+. But under load shows no more then 1400rpm. I marked the "gas lever" at 2400 rpm. So I know I run actually 2400. But I cannot reeve it higher. Is this a tachometer problem? The Yanmar 4JH3TE engine gets the tachometer readings from the flywheel not the alternator. Or has it something to do with Maxprop? Or fuel filter or fuel pump?
Any help is very much appreciated.
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Old 27-05-2020, 06:19   #2
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Re: Maxprop Cutlass bearing Low RPMs

OK first you are WAY overpropped, meaning that your prop has way too much pitch, like being in way too high a gear in an automobile, you need to get that fixed ASAP, your so overpitched its likely to cause engine damage if you don’t.

Secondly, I would use a Cutless bearing with a naval brass sleeve and not a plastic one, many will install their Cutlass with epoxy to take up any fitting issues, mine slips in as well, but what I do is to slip it in with the screws out and then take a center punch and mark the center of the holes in the Cutlass bearing, slide it rearward and then drill these marks pretty deeply and slide the Cutless back in and screw the screws into the depressions I drilled, and I use blue loctite on the screws too.

I believe the yard had to remove the prop to replace the Cutless but they apparently messed up putting it back together. I don’t believe there is any problem with them installing the next size screws, perhaps the threads were messed up and they had to, a hose clamp is not a proper fix.
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Old 27-05-2020, 06:58   #3
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Re: Maxprop Cutlass bearing Low RPMs

Thank for the fast reply. Maybe I was not clear with my description of the cutlass bearing. It is a metal brass bearing. Beneteau does not have the usual "hanger type" to hold the shaft. It has a fiberglass pipe sticking out of the hull. I will try to attach pictures.
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Old 27-05-2020, 07:26   #4
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Re: Maxprop Cutlass bearing Low RPMs

being familiar with Beneteau, I can say the same thing. The cutlass bearing extends out beyond the fairing.
There are likely several reasons for this (a) getting the cutlass bearing as close to the prop reduces the amount of shaft extending beyond the bearing, reducing shaft vibration and (b) having it stick out like that makes future removal easier as one can fit a vice-grip or other tool around it to twist it out.
(c) I wonder about this on my Beneteau. The boat was re-engined from Volvo to Yanmar by previous owner, and this may have pushed the shaft back a bit more than original, also requiring an adjustment of the cutlass bearing location.
(d) My boat was also fitted with one of these " flexible" couplings, which also extends the length of the protruding shaft.
(e) and finally, fitting a maxprop, may have meant a prop with larger diameter, requiring more tip clearance, hence having to be pushed back some, together with the cutlass bearing.
Could be any of the above ??
Hope this provides some guidance.
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Old 27-05-2020, 08:39   #5
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Re: Maxprop Cutlass bearing Low RPMs

another thought occurred to me...to remove a maxprop from the shaft one has to disassemble it and in putting it back on, especially by a yard serviceman who may not be familiar with a maxprop, it's possible the pitch settings were altered accidently...just a wild guess here...but an altered pitch can play havoc with you engine rpm settings..
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Old 27-05-2020, 08:42   #6
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Re: Maxprop Cutlass bearing Low RPMs

Very over pitched by the sound of it. On mine there are two screws. Turning them the set amount (quarter turn, half turn can't remember) increases the rpm by 500 revs each turn.

Best bet is to read the manual for your prop.

Mark.
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Old 27-05-2020, 08:49   #7
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Re: Maxprop Cutlass bearing Low RPMs

So the stern tube is fiberglass? I can’t imagine how set screws will hold very well in glass, I don’t have any recommendations.
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Old 27-05-2020, 09:03   #8
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Re: Maxprop Cutlass bearing Low RPMs

yes, I have attached a pic of the Bennie shaft log on my boat when it was originally hauled out. As you can see the bearing sticks out quite bit.
I believe there is a metal tube of some kind inside the fiberglass fairing, but I have never investigated this further.

I have not had any problem with this, even though it looks a bit awkward. The cutlass bearing looks like it is barely in there, as these are generally not very long...4" or thereabouts.
Attached Files
File Type: pdf Bennie Shaft.pdf (96.9 KB, 201 views)
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Old 27-05-2020, 09:12   #9
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Re: Maxprop Cutlass bearing Low RPMs

My stern tubes were fiber glass.
There were usually two set screws one each side of the keel.
These were buried in the glass and putty'd over.
The cutlass bearings were a tight fit in the glass, usually had to be driven in lightly.

I'm unclear.... is 2400 rpm your max rpm or just where you are at 7 knots speed?
If max rpm, then I would want a bit more available... depending on what HP you actually have at 2400 rpm. (check Yanmar power curve) I'm not a big fan of running those engines at 3600 rpm though. They rate these engines at very high rpm so they can call them more HP and lightweight.
The yard should be responsible for resetting the Max Prop for you if they got it wrong. Did you make more RPM before?
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Old 27-05-2020, 09:16   #10
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Re: Maxprop Cutlass bearing Low RPMs

If you look closely, you can see a set screw at the very tip of the shaft log on the bottom. It may not be a set screw, as set screws are typically very short, but could be a longer screw of some kind to reach up thru' the fairing to the cutlass bearing..

I could not tell you why I did not take a closer look at this setup when the boat was first hauled as my interests were elsewhere. I had a very experienced boat surveyor with me at the time of the haul and he had no comment on this either. Normally, something like this would cause my heart to skip a beat.

Regardless, it has never been an issue of any kind.

The new engine was put in the boat in St. Augustine, by a very reputable person I'm told, so there must have been a reason for this setup.
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Old 27-05-2020, 13:06   #11
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Re: Maxprop Cutlass bearing Low RPMs

All else being equal, if it was working well before the haul, and not after, I beleive A64 is correct, the setting on your Max Prop was changed, overpitching it. As there are several styles of maxProp, you need to know which one you have to know how to correct it. Any of them but a Classic can easily be done underwater by a competent diver/tech. I am currently doing it to a Classic, but only because i have to.
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Old 27-05-2020, 13:28   #12
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Re: Maxprop Cutlass bearing Low RPMs

yep, earlier max props had to be disassembled to access the gears that set the pitch.....newer one's can be done from the outside...

but, if the maxprop had to be "removed" it was likely the classic version, and thus the possibility of the pitch being incorrectly set on putting it back on.

The OP states that the " The yard took the Maxprop off unnecessarily to get to the cutlass bearing. They had a hard time configuring the correct setting when assembling it. It looks ok to me but I don't know anything about Maxprop settings.

This tells me that there is high likelihood it is the classic version.

For what it's worth, I concur with the likely possibility of the pitch being incorrectly set when re-assembling it, this would account for the anomalies in boat boat vs. engine rpm.
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Old 27-05-2020, 13:30   #13
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Re: Maxprop Cutlass bearing Low RPMs

boat " speed" vs.engine rpm.....aging eyes...
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Old 27-05-2020, 13:33   #14
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Re: Maxprop Cutlass bearing Low RPMs

Quote:
Originally Posted by Peterbreit View Post
I have a problem with the cutlass bearing on my 2000 Beneteau 461. When hauled the surveyor noticed the cutlass bearing coming out about 1 inch. When I looked at it I found one of the little (really LITTLE) set screws missing. I was able to push the cutlass bearing back in with my fingers! Question: The plastic tube holding the cutlass is very thin. There is just no good way to put a serious set screw in. Unfortunately the yard reamed out the holes to fit a thicker screw but no I am SOL.
I would have put in the old little screws and put a SS hose clamp around it. We did put a donut shaped zinc on the shaft between the cutlass bearing and the Maxprop.
2.Problem The yard took the Maxprop off unnecessarily to get to the cutlass bearing. They had a hard time configuring the correct setting when assembling it. It looks ok to me but I don't know anything about Maxprop settings. I learned a lot fast.
The boat runs ok about 7knots at ~2400 rpm. But the tachometer never goes above 1400 rpm. What gives ?? I changed both fuel filters. When NOT under load (prop-transmission not engaged) it reeves up to 3500+. But under load shows no more then 1400rpm. I marked the "gas lever" at 2400 rpm. So I know I run actually 2400. But I cannot reeve it higher. Is this a tachometer problem? The Yanmar 4JH3TE engine gets the tachometer readings from the flywheel not the alternator. Or has it something to do with Maxprop? Or fuel filter or fuel pump?
Any help is very much appreciated.
The yard owes you a haul out to reset the MaxProp to the right settings. Since there are 264 possible ways to assemble one of these Classic MaxProps, if they didnít know what they were doing the chances of getting it right are pretty close to zero. To be fair, it can be quite hard to figure out what the settings are as you take it apart, but that doesnít excuse putting it together in a random orientation and sending you on your way.

Of course the question then is, do you want the same knuckleheads who messed it up in the first place re-doing it?

There are a couple ways to know what the right settings are. If the Previous Owner was a good boy, somewhere on board is the manual for the MaxProp with the settings that were used marked and noted. That would get you back to where you were, assuming that was correct.

An alternative, is to call MaxProp USA and get their advice as to what the settings should be. With details about your boat and engine, they will have a very good idea. And get you very close.

And you have learned an important life lesson: the only person who cares at all about your boat is: YOU.
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Old 27-05-2020, 14:10   #15
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Re: Maxprop Cutlass bearing Low RPMs

Since the original issue was the cutlass/cutless bearing, regardless of style, the prop would need to be removed, unless the shaft was disconnected from the transmission and the bearing done from the other end of the shaft. Prop removal is the simpler method.
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