When I had my new Yanmar GM20 installed in my 1973 E-29 the mechanic installed the rear motor mounts at a 45 degree angle. My surveyor says that the motor mounts won't work this way, according to Yanmar, but if I install them inline then the motor will stick out into the salon. The engine runs well and when I watch the mounts they seem to be doing their job. Any thoughts about this, am I going to have some kind of terrible problems in the future?
jmoses
Member III
Engine mounts (?)
I guess I don't understand the scenario....are the mounts inclined 45 degrees (i.e. off the horizontal)? or are they 45 degrees off the centerline of the engine? I don't get the picture. Also, I don't understand how a small change in the engine mounts will make for a change in engine's location.....either the engine aligns with the drive/prop shaft or it doesn't. Jacking the engine or mounts around to fit the engine into a space is not the way to do it.
Also, WHY did the surveyor say they won't work....I dislike it when a surveyor, mechanic, etc. offers an opinion then doesn't back it up with a valid reason.....or a way to solve the problem "Hey that won't work......good luck!" is not professional advice.
If the mounts are 45 deg. off the horizontal (i.e. inlcined) then he/they are correct as the mounts will sag in the direction of the incline and cause the coupling and engine alignment to change for the worse and stess the whole engine and dirve train alignment. Yes, this will cause a problem later.
If they are 45 degree off the engine centerline, I don't see a tremendous problem with that as the mounts are intended to keep the engine from torquing around and keep it level. This is with a big caveat as all mounts are not created equal and may be damages if installed incorrectly - read the engine manual regarding mounting.....the manufacturer has done their homework and it's your warranty (which may be voided by an incorrect installation).
Also, maybe some shims are in order instead of jacking the mounts around. Usually there is a way to do the install correctly with out compromising the engine mounts....just have to think it through (laziness is no excuse!).
John M
I guess I don't understand the scenario....are the mounts inclined 45 degrees (i.e. off the horizontal)? or are they 45 degrees off the centerline of the engine? I don't get the picture. Also, I don't understand how a small change in the engine mounts will make for a change in engine's location.....either the engine aligns with the drive/prop shaft or it doesn't. Jacking the engine or mounts around to fit the engine into a space is not the way to do it.
Also, WHY did the surveyor say they won't work....I dislike it when a surveyor, mechanic, etc. offers an opinion then doesn't back it up with a valid reason.....or a way to solve the problem "Hey that won't work......good luck!" is not professional advice.
If the mounts are 45 deg. off the horizontal (i.e. inlcined) then he/they are correct as the mounts will sag in the direction of the incline and cause the coupling and engine alignment to change for the worse and stess the whole engine and dirve train alignment. Yes, this will cause a problem later.
If they are 45 degree off the engine centerline, I don't see a tremendous problem with that as the mounts are intended to keep the engine from torquing around and keep it level. This is with a big caveat as all mounts are not created equal and may be damages if installed incorrectly - read the engine manual regarding mounting.....the manufacturer has done their homework and it's your warranty (which may be voided by an incorrect installation).
Also, maybe some shims are in order instead of jacking the mounts around. Usually there is a way to do the install correctly with out compromising the engine mounts....just have to think it through (laziness is no excuse!).
John M
Because of the hull shape the rear engine mounts cannot be placed inline with the engine, you would have to shave an area out to get the mounts to be level. Unfortunately the area that you would have to shave is the hull so the mounts were installed along the angle, made by the hull, along the back of the motor. The Atomic 4, previous engine, had the mounts further forward and so could be installed in a straight line. The new type mounts produced for this new engine are a lot longer and are mounted a lot further back on the new engine. So imagine looking down, from above, at the engine. The front mounts will be inline, the rear mounts would stick out at 45 degree angles. They would still be level on the on engine bedding area but just would be mounted along the curveture of the hull along the back. Does this make sense to you?
As far as the surveyor goes he said that he called Yanmar and they said that the mounts have to be installed parallel to the motor, but when I checked in the installation manual they state that the proper mount has to be installed front to front and rear to rear but they don't say anything about parallel installation. When I had my 50 hr. service done the mechanic had to place taller shims under all of the motor mounts but he didn't have anything to say about the positioning of the rear mounts.
jmoses
Member III
Engine mounts- Take 2
I sort of see the picture but I am still not exactly clear.
Has the engine alignment been checked lately? I'm assuming that's why the mechanic shimmed the engine? I'd keep an eagle eye on the engine's aligment as that's what will be affected if the mounts are askew or installed incorrectly. Or the transmission will wear excessively due to stress of the engine moving around on the incorrectly installed mounts. Keep in mind, they may be fine.....but I'd get a second opinion and document everything (see last paragraph).
With any engine install it's most important to have the engine mounts (and engine!) as close to horizontal as possible. Most manufacturers have a limit on the angle of inclination an engine may take (most are no more than ~ 10 degres). I realize horizontal mounts are not always possible and with small engines it is not as critical as with 4 ton 3,000 HP engines.
If you could attach a digital picture that would help 1,000 %!
I quess I'd get another mechanic in from another Yanmar dealer and have them give it an eye ball (or a mechanically inclined surveyor - most will do a quick look-see gratis if in the area). Since I'm not there and can't envision the entire situation I'm at a loss. If this is a new engine installation and it craps out (transmission) or causes drive train damage later due to an incorrect installation I'd be getting stuff in writing from the dealer, take pictures and have the mechanic sign off on the installtion to CYA (Cover Your A**). The paper trail will be helpful later for the insurance claim if required.
Again, I hate to say it, but there is no easy "drop-in" re-power scenario (unless the same engine). Most are fought with issues such as this....please take no offense, but I've come across many repower problems that were sold as "Simple! Just drop it in" situations with the owner left holding the bag and no assitance after the check clears.
John M.
I sort of see the picture but I am still not exactly clear.
Has the engine alignment been checked lately? I'm assuming that's why the mechanic shimmed the engine? I'd keep an eagle eye on the engine's aligment as that's what will be affected if the mounts are askew or installed incorrectly. Or the transmission will wear excessively due to stress of the engine moving around on the incorrectly installed mounts. Keep in mind, they may be fine.....but I'd get a second opinion and document everything (see last paragraph).
With any engine install it's most important to have the engine mounts (and engine!) as close to horizontal as possible. Most manufacturers have a limit on the angle of inclination an engine may take (most are no more than ~ 10 degres). I realize horizontal mounts are not always possible and with small engines it is not as critical as with 4 ton 3,000 HP engines.
If you could attach a digital picture that would help 1,000 %!
I quess I'd get another mechanic in from another Yanmar dealer and have them give it an eye ball (or a mechanically inclined surveyor - most will do a quick look-see gratis if in the area). Since I'm not there and can't envision the entire situation I'm at a loss. If this is a new engine installation and it craps out (transmission) or causes drive train damage later due to an incorrect installation I'd be getting stuff in writing from the dealer, take pictures and have the mechanic sign off on the installtion to CYA (Cover Your A**). The paper trail will be helpful later for the insurance claim if required.
Again, I hate to say it, but there is no easy "drop-in" re-power scenario (unless the same engine). Most are fought with issues such as this....please take no offense, but I've come across many repower problems that were sold as "Simple! Just drop it in" situations with the owner left holding the bag and no assitance after the check clears.
John M.
Motor mount bases are generally glassed in to the hull to provide a
flat (not 45 degrees !) surface for the engine mount. This requires about
6" clearance from the bottom side of the engine to the furthest away
part of the shape of the hull (2" base angle + 2.5" motor mount + 1" clear)
Who manufactured the motor mounts (www.bushingsinc.com) ?
They will tell you the specs on how the mounts are to be installed.
I agree with John that 10-15 degrees is Maximum.
The exhaust riser is part of your wet exhaust design and the height is
provided by the engine mfg to keep water and water vapor out of your
engine. As you want to change it, get the new design BLESSED by the mfg
before you do ANYTHING !
flat (not 45 degrees !) surface for the engine mount. This requires about
6" clearance from the bottom side of the engine to the furthest away
part of the shape of the hull (2" base angle + 2.5" motor mount + 1" clear)
Who manufactured the motor mounts (www.bushingsinc.com) ?
They will tell you the specs on how the mounts are to be installed.
I agree with John that 10-15 degrees is Maximum.
The exhaust riser is part of your wet exhaust design and the height is
provided by the engine mfg to keep water and water vapor out of your
engine. As you want to change it, get the new design BLESSED by the mfg
before you do ANYTHING !
Randy Rutledge
Sustaining Member
The angle of slope front to rear of the mounting of an engine as well as the height is determined by the angle of the prop shaft. The prop shaft and the crankshaft must form a straight line and the prop shaft is the nonadjustable part. The transmission coupler and the shaft coupler must be in alignment. If the couplers are unbolted and drawn close they must align so that the gap between is the same at all points of the circumference and the couplers match. There will be a small amount of movement in the prop shaft. With the free movement of the prop shaft centered the couplings must align and make contact at all points round the bolt pattern. The only way to achieve this is by moving the engine by adjusting the motor supports.
First
Adjust the height of the back supports and side to side to match the couplings in line.
Next
Move the front of the engine up closes the gap at the top.
Move the front down closes the gap at the bottom.
Move the front of the engine left closes the gap at the left.
Move the front right closes the gap at the right.
Each move affects the others so you repeat until perfect alignment or the beer runs out.
(FOR BEST RESULTS DO NOT START THE BEER UNTIL THIS IS DONE)
The problems of a misalignment are bearing wear, seal wear or the real fear shaft flex that causes the prop shaft to break. At 2800 RPM the break would be bad; in ski boats I have seen hull damage. (Big holes).
Is there a way to make brackets to bolt to the engine and mount the rear mounts to the bracket forward of their current position and have then upright; instead of at an angle?
First
Adjust the height of the back supports and side to side to match the couplings in line.
Next
Move the front of the engine up closes the gap at the top.
Move the front down closes the gap at the bottom.
Move the front of the engine left closes the gap at the left.
Move the front right closes the gap at the right.
Each move affects the others so you repeat until perfect alignment or the beer runs out.
(FOR BEST RESULTS DO NOT START THE BEER UNTIL THIS IS DONE)
The problems of a misalignment are bearing wear, seal wear or the real fear shaft flex that causes the prop shaft to break. At 2800 RPM the break would be bad; in ski boats I have seen hull damage. (Big holes).
Is there a way to make brackets to bolt to the engine and mount the rear mounts to the bracket forward of their current position and have then upright; instead of at an angle?