M25xp, convert from 3 point mount to 4?

JSM

Member III
While eyeballing Beta Marine engines at the Chicago Boat Show this weekend I mentioned to the rep my problems with trying to vanquish vibration at certain RPM with the M25xp on my E34. He claimed that the largest cause of vibration problems associated with this engine is due to the 3 point mounting system and suggested that I look into switching to 4 mounts.
Looking at the diagram for the crankcase group / mounts on Marine diesel Direct this looks like it may be possible using bracket #302969 and eliminating the bracket (#29 on the diagram) that makes up the front mounting point.
I can find no mention on the net of anyone doing this however there is currently a M25xp for sale on Ebay that has these brackets in place for the front mounts.
http://www.ebay.com/itm/Rebuilt-Uni...ash=item3ad71ca078:g:vOoAAOSwQYZWw2cJ&vxp=mtr
Any thoughts ?
Thanks
 

EGregerson

Member III
4 mounts

I didn't do this to my universal; but when i repowered, the new motor (volvo) has 4. 1st, before going to the trouble; make sure your prop is balanced and shaft alignment is proper. If these are ok; maybe the motor simply needs new motor mounts. Also check mounting bolts (lag screws) to make sure they're tight; also check the screwholes through into the fiberglass to make sure the vibration hasn't caused the mounting screw to auger out the hole. If all that is good and u still want to add a 4th foot, remember the 2 new mounting points were not designed for that; the floor is not as thick at that point. I've considered mounting machined aluminum plates under the mount to add support. Haven't done it yet; I recall the installer saying that the bulk of the motor's stress / force is on the 2 rear mounts. So maybe it doesn't really need the plates. But I did install larger lag screws to beef them up. Good luck with the project; post pics if u add the mounts.
 

JSM

Member III
Thanks. Last year we rebuilt the drive train. New shaft , coupler, cutless bearing , motor mounts and stuffing box. The prop was balanced as well. I had the yard do an alignment after we finished the work and I rechecked the alignment again at the end of the season and it was only slightly off. I did discover that the rear lag screw on the front mount has lost its bite and needs to be dealt with.
While going thru the owners manual last night I discovered a chapter on vibration that pretty much describes my situation as normal.
:rolleyes:.Maybe I should just drop in a larger lag screw and leave well enough alone!
 

EGregerson

Member III
prop

do u have a 2 blade or 3 blade prop? i think i heard a 3 blade turns better (smoother). My installer had to have new front mount flanges fabricated since the engine compartment wasn't designed for 4; and it was too far to the floor. I attached a pic; u can see where the forward mounts touch the floor; it's not reinforced at that point. Plates of some sort, aluminum, maybe starboard would strengthen it. This motor does run a lot smoother than the universal did.
 

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JSM

Member III
Looks like fun! I am going to try to get to my boat this weekend and eyeball everything. Looks like if I do this I would have to extend the stringers further forward.
(Maybe I should just stop talking to strangers at boat shows ):)
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Maybe I should just drop in a larger lag screw and leave well enough alone!

I'm for that. The M25 range inherently have vibration, and replacing the old rubber in the three mounts probably helps. Also selecting a happy rpm.

For me, going to four mounts sounds like a lot of work for an uncertain payoff.

It would be good to hear from somebody who has done it, and their report.


(For what it's worth, my current M40 4-cylinder is quieter and vibrates less, but I liked my M25 fine)
 
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EGregerson

Member III
just a thot

could u add forward side mounts and leave the single front mount intact? that might eliminate the need to build up/ reinforce the area for the new mount; u would have 5 mounts. Odd? maybe but i'd bet it would be the smoothest running 25xp in town.
 

JSM

Member III
Looking at the diagram it appears that the bracket for the front mount (#29) is bolted into where the new front brackets would have to go. Leaving it in place to provide a fifth mount doesn't look like an option.200142-3.jpg
Or maybe, just maybe those two "ears" at the rear of the forward mount bracket (29) will line up perfectly over the stringers to accept a new mount on each side. :rolleyes:
 

Kenneth K

Contributing Partner
Blogs Author
Since the payoff of going to 4 mounts is unknown, I'd want to minimize the labor & costs involved. Maybe you could have a bracket such as this fabricated, remove the center motor mount, and drill and bolt this to the sides of the existing mounting bracket. You'd have a lot of flexibility in designing the height (A) and ear-width of your fabricated bracket to accommodate varied placement of the new side mounts. Just a thought.....

Ken
 

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Ian S

Member III
Hi JSM. I have a 1990 E32-3 up in Waukegan, I see your in Chicago somwhere? I had a vibration issue that drove me bonkers! I am also happy to report that I have solved it! I checked alignment, coupler faces, prop balance, strut alignment,compression, injectors, and nothing worked and everything checked out ok.
The solution, involved ditching the factory cast three point engine bracket. I simply removed it and had two new mounts fabricated. If you look where the factory bracket mounts you will simply put your new brackets there. You will also find that you have plenty of room to set your new mounts on the engine bed just as the rear mounts are. I also replaced the existing mounts with new mounts from iso-flex. I dd not really document the process but I can certainly get you set up and going in the right direction. Also worth noting that I too had the lag screw slipping in its thread. The whole design is quite frankly junk! and poorly thought out. Every engineer I have spoken with on this matter says the same thing. You can NOT properly control the torsional and axial forces of an engine from three points with any repeatability or precision. My boat is smoother, quieter, and is a joy under power now. The alignment stays put- finally. Feel free to PM me and I will give you my PN. worth noting I also owned a rigging business for a time and have worked as a professional ship wright.

PS The post you probably read was my old post asking for help and received the Accept it and live with it method.
Not the way I roll! If you think theres something wrong there is, period!

Best Regards: Capt. Ian
50T USCG Master.
 
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bigd14

Sustaining Member
Blogs Author
The custom brackets make a lot of sense. Looks like they could just bolt on easily to the sides with four bolts. Capt Ian, is this where the new mounts ended up on yours?

Thanks,

Doug



Engine Mounts.jpg
 

JSM

Member III
Big thanks Capt.Ian ! PM sent . Here's shots of both the left and right sides of the engine. The two tabs that are part of the forward mounting bracket (#29 on the diagram) appear to be set up to sit on mounts.
My thinking is to build up the stringers/engine bed and add the new mounts.20170121_135739.jpg20170121_140016.jpg
 

Ian S

Member III
Hey Doug, My engine bed is a bit different than yours, but yes as long as you can clear the crankcase you'll be fine. I have a fabrication shop near me with a huge press brake. find a place that does structural steel. I gave them the drawing of what I wanted made, copied the mounting hole dia. / spacing from the original bracket (all metric FYI), and purchased the appropriate bolts. I gave the new brackets a quick rattle can of primer and gold paint to match. They bent the offsets, sheared the pieces (4 total) and performed the welding. The parts were all 3/8" x 2-1/2" bar stock. I think it cost me 50 bucks. Took me about three hours to get the new mounts installed and align the engine. The hardest part believe it or not was pre-aligning the new mounts & drilling the holes for the new lags. I had to jockey the engine off to either side to clear the drill and marked the holes with a sharpie. The bracket offsets / height and lengths were of critical dimension due to the limited vertical adjustment in the mounts themselves and having to hit the engine bed on the money athrwartships (no real adjustment there). Don't worry if the mounts do not hit the exact same relative spots on either side of the engine bed, as the beds are not all that true to the boat / log / strut angles. All that matters is the alignment of the shaft / engine I found the trick was to use a 12"+ bit so i could get over the top of the engine, the shank of the bit then cleared the crankcase and accessories.
I also supported the front of the engine with and extra block and tackle (handybilly) rigged through he companionway and supported the harmonic balancer /crankshaft. These engines are quite light and you are still supported on the rear mounts as you are doing all this. You will replace the rear mounts after you have dealt with the new fronts and then replace those one at a time. The engine is supported well enough on three to permit changing each one out individually. Of course I performed another alignment once the boat was back in the water for a couple of weeks. It should be stated and stressed that a true alignment (opposed to rough alignment) can ONLY be performed and checked with the boat in the water with average rig tension. Boats flex ALLOT!


I will try to dig up the drawings I made as well as some pictures when I find the time. Your brackets will be different than mine but Im certain if you give the whole process some thought, take your time getting the measurements you will get it all figured out. I assure you ditching that crappy aluminum front bracket and the single mount will make a world of difference!


Capt. Ian
 
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Ian S

Member III
a few rather vague pictures.

Hi guys, I hope this helps a bit, or at least gives a sense of what I did. Each boat model will be different but the premise remains the same and I believe can be accomplished on just about any model with a 3 point mount. Someone will have to help me figure out how to get these photos to load correctly oriented as they were in the raw files? sorry, just down load and rotate on your own if neccesary.

Capt. Ian
 

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bigd14

Sustaining Member
Blogs Author
Looks great Capt. Ian! Thanks for posting the information. I will have to play around with it for awhile to see if it would be better to build up the engine beds or just manufacture a weird bracket and have the mounts at a 45 degree angle.

Thanks again.

Doug
 

Keith Parcells

Sustaining Member
Capt. Ian,

What are the new motor mounts bolted into on the stringer? Is there plywood beneath? Did you use lag screws? If not, what was used? I take it that you are happy with how secure it is, right?

It sure looks good compared to the tree point mounting!
 

JSM

Member III
Thanks Capt. Ian. Your pics are exactly what I had in mind. My problem is that my engine bed is pretty much the same as Doug's and my stringers fall short. How critical is it that the front and rear mounts be parallel to each other ?
Would it be ok to extend the brackets downward and anchor the mounts to the engine bed as per Doug's diagram or would extending the stringers out using angle iron or building up the engine bed be more effective?
 

bigd14

Sustaining Member
Blogs Author
I mocked up two scenarios.

Scenario 1. The first photo shows a cardboard template of a steel or aluminum backing plate that would accept the engine mounts in line with the engine. Two problems with this scenario. First, the starboard mount has no forward clearance beyond the edge of the engine bed, due to the engine cover tucking up against this area. This would cause the mount to sit next to the dipstick (second photo), which would need to be moved. Second, the aft outside ends of the engine mounts have very little clearance against the inside of the upper engine beds. I could potentially chip some of this away, but I don't want to compromise any strength. This limits adjustment, and also does not give very much clearance beside the engine mount frame (which I plan to leave in place) to install an ear to attach to the mount (third photo)



Mounts and Plate Parallel.jpgStbd Mount Dipstick.jpgPort Mount Parallel.jpg


Scenario 2. This would simply angle the two forward mounts to align with the existing engine beds. I would use an aluminum or steel plate under these, tapped to accept studs and permanently lagged into the engine bed beneath. And a custom angle bracket that attaches to the forward part of the engine mounting frame. There is more clearance here for the mounts both on the beds and next to the mounting frame on the engine. The disadvantage is that the mounts are at a 45 degree angle to centerline and I understand that they are manufactured to resist forward motion, but allow some sideways motion. The angle may negate that design element. I could leave the forward center mount in place and have 5 mounts (first photo below), but that may complicate engine alignment.

Mounts Angled Front View.jpgMounts Angled on Beds.jpg

At this point I am leaning toward Scenario 2, simply because it's easier. I could also just leave well enough alone and stick with the three mounts. But, if I can find a way to reduce vibration, while I'm in there...:egrin:
 

Frank Langer

1984 Ericson 30+, Nanaimo, BC
Doug,
With your engine removed, can you determine the structure of the stringers that support the engine. Is it just fibreglass or is it wood converted with a thin fibreglass layer, or something altogether different? I am puzzling about the engine mounts on our 1984 E30+ and would like to know what those lag screws go into.
Thanks,
Frank
 
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