Problem with PS 37 engine mounts

[waypt1]

The following pertains specifically to PS 37’s with a Yanmar 4JH2E engine. I have no idea if the same condition exists with other engines or other PS models.

The short version – The engine bed on a PS 37 is almost four inches too short to install a Yanmar 4JH2E engine as Yanmar intended it to be installed. To get around this problem Pacific Seacraft reversed the aft engine mount brackets. In this configuration the engine bed is still almost one inch too short. The solution to this problem (at least on my PS37 #347) was to force the rubber (flexible) engine mount over so the stud on the rubber engine mount would go into the hole in the aft engine mount bracket. There is a picture of a “good” and a “bad” rubber (flexible) engine mount installation in the Yanmar operation manual. My rubber (flexible) engine mounts were forced so far over the metal top of the mount was almost touching the metal bottom of the mount. The rubber was so compressed, there was no flex remaining for vibration isolation.

The longer version – The front to back, center to center distance for the studs on the rubber (flexible) engine mounts for a Yanmar 4JH2E engine is 19.39 inches. By reversing the aft engine mount brackets this dimension is changed to 16.60 inches. The front to back, center to center distance for the studs on the rubber (flexible) engine mounts on my boat is 15.75 inches. If the engine was lowered down with the studs on the forward rubber (flexible) engine mounts aligned with the holes in the forward engine mount brackets; the studs on the aft rubber (flexible) engine mounts would miss the holes in the aft engine mount brackets by 0.85 inches (16.60 inches minus 15.75 inches).

I discovered this problem when I was installing a set of new rubber (flexible) engine mounts. I had noticed that the old mounts never looked “right” but having bought an almost new “Mercedes” I did not expect there to be major engineering faults with the boat. Now, having invested $600 in a set of new rubber (flexible) engine mounts, I became intimately involved in learning how these pieces were supposed to fit together. The old rubber mounts were totally destroyed with the mounting studs sheared off on the forward mounts and the rear mounts bent and distorted. The mounting studs on the new rubber mounts weren’t lining up with the engine mounting brackets and nothing was making sense until I got out the engine parts manual which has detailed drawings with dimensions of the engine. You can imagine my surprise when I got out the tape measure and discovered my 15.75 inch center to center dimension when the book showed it should be 19.39 inches. By studying the pictures I also discovered the aft engine mount brackets had been reversed (and swapped side to side). I still had trouble believing that Pacific Seacraft installed the engine like that but the tape measure didn’t lie.

The solution – I bought new aft engine mount brackets (the old ones were bent out of shape after being forced on a leaned over stud for 2500 engine hours) and had a machine shop modify the new brackets by welding on an extension and drilling the hole in the correct location. I also had a gusset welded on the one side of the brackets. The pieces all fit and my rubber (flexible) engine mounts now look like the “good” picture in the Yanmar operation manual. More importantly, we can not believe how quiet the engine is now. For the first time ever, our engine truly has flexible engine mounts.

I have discussed this issue with the current owner of Pacific Seacraft, Steve Brodie. Pulling out a few quotes from his response to me:

“It would appear that your situation is not entirely unique”

“I believe the gusseted bracket is the proper fix and is similar to the brackets that we are currently using for other models. “

“We will work to try to identify which model years may be effected by this issue to make sure we have good answers for customers experiencing the same problem.”



This wasn’t an easy fix but it needed to be done. After a few weeks, all the nicks, cuts and bruises on my hands have healed and my hands no longer have grease imbedded in them. Now all that remains is the very, very quiet operation of the engine. A quick check with a tape measure will tell you if you have the same problem. Better yet, look at the rubber mounts and see if the installation is "good" or "bad".

Roland Snyder
s/v Wayward Wind
PS 37 #347

[SVArgo]

Hi Roland,

I replaced my front mounts after ripping them in two on a submerged mooring pendant. I bought two aft mounts and had planned to get them on this summer or fall. Do you have any pictures of what your final installation looked like? Or better yet, specs for the mount you had fabricated? I thought my mounts were just worn down in the back, but I see what you mean and they definitely won't balance right and provide the noise and vibration dampening that way.

Ryan

[waypt1]

For some reason I can't attach pictures. When I try to upload a 14 kb photo I get a upload failed message. I will post photos if someone will tell me how.

Roland

[RainDog]

You can find instructions and help here: http://www.sailnet.com/forums/sailne...-pictures.html

[waypt1]

Old rear motor mounts. Note how they have been forced over.



Motor mount installed with new modified bracket. Note how hole in engine bed line up with holes in motor mount.




Comparison of new modified engine bracket and original engine bracket.



Another comparison of new modified and old, slightly bent, engine brackets.

The new bracket was modified by cutting off the short (horizontal) leg of the bracket to get rid of the misplaced mounting hole; welding on an extension to permit drilling a new mounting hole 0.85" from the center of the old hole.

Roland

[SVArgo]

Thanks Roland. 0.85" Center to Center is the magid number then? I'll do some forensics on mine to check and see if the error was consistent.

Cheers,
Ryan


Another comparison of new modified and old, slightly bent, engine brackets.

The new bracket was modified by cutting off the short (horizontal) leg of the bracket to get rid of the misplaced mounting hole; welding on an extension to permit drilling a new mounting hole 0.85" from the center of the old hole.

Roland[/QUOTE]

[waypt1]

In response to Ryan's question "Is 0.85" the magic number?"

On our boat the installed, fore and aft, center to center distance on the rubber motor mounts is 15.75". With that center to center dimension for the motor mounts, the hole in the engine bracket needs to be moved 0.85". If Pacific Seacraft used a template to drill the holes in the engine bed, then the 15.75" dimension will be consistent from boat to boat and 0.85" will be the needed correction. If the center to center dimension for the motor mounts is not 15.75", then the needed correction will not be 0.85"

Roland

[SVArgo]

Originally Posted by waypt1

In response to Ryan's question "Is 0.85" the magic number?"

On our boat the installed, fore and aft, center to center distance on the rubber motor mounts is 15.75". With that center to center dimension for the motor mounts, the hole in the engine bracket needs to be moved 0.85". If Pacific Seacraft used a template to drill the holes in the engine bed, then the 15.75" dimension will be consistent from boat to boat and 0.85" will be the needed correction. If the center to center dimension for the motor mounts is not 15.75", then the needed correction will not be 0.85"

Roland

After much procrastination, I'm getting ready to tackle this issue. The best I can measure, the end to end distance of my flexible mounts, as installed is 24-3/8". Assuming the mounting bolt is centered on the flexible mount means that my center to center distance is 16-5/16" (24-3/8" - 8-1/16"). If the correct center to center is 16.6" then that would mean my mounts are out 0.2875".

I'm not 100% on all of this yet, but can say that my aft mounts are such that the after edge is bottoming out, so something has to be done. If my mounts are bent as Roland's were, those measurements may not be as surefire as I'd like.

Ryan