To compliment other posts about the M35B damper plate, here is my experience. At slightly over 700 engine hours, I discovered black/grey power in the starboard rear area of my engine compartment. I first though it was from the alternator belt but not so. Shortly later I noticed a chattering sound in idle that would decrease when engine rpm increased. I think the clattering had been there for some time but I just did not pay attention to it. Based on other posts, I decided the problem was likely the damper plate. I disconnected the transmission output shaft from the prop shaft, raised the engine rear, removed the transmission, and removed and replaced the damper plate. The damper plate has a non-metallic center which was coming apart with chunks in the bell housing bottom. These chunks were being ground into fine power that was blowing out the timing mark viewing hole in the starboard side of the bell housing. I replaced the damper plate and problem solved. Upon request, I will email a fairly detailed summary with pictures of how I raised the engine rear and removed and replaced the damper plate. I did all the work and the damper plate cost $404.32 at R. B. Grove, Inc. in Pensacola. Below is a description of the pictures.
DP01.jpg: New damper plate on left and old on right.
DP02.jpg: New damper plate.
DP03.jpg: Old damper plate.
DP04.jpg: Old damper plate showing chunks removed from bell housing.
DP05.jpg: Part number tag for new damper plate.
DP06.jpg: Port rear engine mount area showing bolt used to raise engine rear.
DP07.jpg: Wood piece used to keep pressure on dripless seal.
DP08.jpg: New damper plate installed in bell housing.
DP09.jpg: Another shot of new damper plate in bell housing.
DP10.jpg: Transmission reinstalled and engine rear still raised.
DP11.jpg: Another shot of transmission output shaft and prop shaft flanges disconnected.
Damper Plate Replacement Procedure:
Remove exhaust hose from muffler then from exhaust elbow and set aside. Observe about one cup clear water in hose which spilled into prop shaft sump.
Siphon water from shaft sump and sponge dry.
Make alignment marks on transmission output flange and on prop shaft flange with file.
Using 17 mm wrench, loosen four bolts connecting transmission output flange and prop shaft flange. Bolts not very tight and nuts & lock washer are to front. No play between flanges so remove all four bolts. Now can turn flanges versus each other but no fore/aft movement of either flange. Clearance between flanges less than 0.003 inches all points.
Remove seizing wire from two prop flange set screws and loosen screws using 3/8-inch open end wrench. Screws not very tight.
Use flat screwdriver to pry prop shaft flange from transmission flange but prop shaft moves back rather than flange moving on prop shaft.
Remove prop shaft flange set screws and shoot WD40 into holes and into cotter key hole but still can not slide flange on prop shaft. Tap flange with hammer but no good.
Using 15/16-inch wrench, remove nuts & washers from rear motor mounts.
Break for lunch.
Begin trying to raise and block rear of motor but can not get a jack or lever board under engine so decide to use a screw mechanism to raise engine.
Remove some of the engine compartment air exhaust hose and blower and push aside.
Using a 6-inch long 3/8-inch diameter carriage bolt with nut and fender washers, raise engine rear to gain sufficient clearance to remove transmission. This means the transmission and prop shaft flanges will barely pass each other when the transmission is pulled back from the bell housing. No need to loosen front engine mounts. See pictures which were taken after transmission was reinstalled. The bolt was put through a hole in the port engine mount flange located behind the hole the mount bolt goes thorough. Block the starboard engine mount flange with wood blocks after the engine is raised as a safety measure.
Disconnect transmission shift linkage and associated bracket and lay on engine compartment floor. Can be seen lying on floor in picture DP_11.jpg.
Remove six bolts holding transmission to bell housing then pry transmission loose using screwdriver at partially unscrewed bolts. Note that two bottom port bolts must be inserted before transmission is fully splined up. Otherwise there is not sufficient clearance to insert later.
Observe chunks of damper plate in bottom of bell housing and remove chunks.
Using 3/16-inch allen wrench, remove five cap screws holding damper plate in place and remove damper. This requires bumping over engine with starter because only one or two screws can be accessed at any given engine rotation position. Exercise extreme care to ensure allen wrench is removed and that ensure engine does not start before bumping over engine with starter.
Note engine rotation is clockwise looking at engine from front or water pump end and counterclockwise looking at engine from rear or transmission end.
Clean bell housing and engine compartment using vacuum cleaner.
Use short board to secure prop shaft in aft position to prevent dripless seal from leaking. See picture DP_07.jpg.
Stop for now and wait on new damper plate.
Receive new damper plate from R. B. Grove, Inc. See picture DP_05.jpg for part number.
Observe hole in starboard side of bell housing, probably to view timing marks. This is where black/grey powder escaped from bell housing.
Install new damper plate using five set screws requiring 3/16-inch allen wrench. Use Permatex Threadlocker Medium Strength Blue which says allows for disassembly or adjustment with normal hand tools. Elect to not use Loctite Threaderlocker Red 271 which says to disassemble, apply localized heat for five minutes at 450°F and disassemble while hot. Tighten each screw as tight as seemed possible without stripping threads or breaking allen wrench.
Drain and flush transmission.
Install transmission using six bolts with lock washers and 17 mm wrench. . Put Permatex Anti-Seize lubricant on transmission shaft splines before inserting into damper plate. Note that two bottom port bolts must be inserted before transmission is fully splined up.
Lower engine rear and, while doing so, simply push motor mount vertical bolts side to side to line up with brackets on engine.
Connect transmission output flange to prop shaft flange with four bolts with nuts and washers to front. Use 17 mm wrenches and tighten as much as possible.
Install two set screws in prop shaft flange and seize with wire after tightening screws fairly tight.
Install shift linkage using two bolts with washers and ½-inch wrench. Grease snap-on connector.
Install two 5/8-inch motor mount nuts and washers using 15/16-inch wrench after cleaning with wire brush and coating exterior very lightly with Vaseline to inhibit rust.
Install exhaust hose using two SS hose clamps each end.
Put duct tape over bell housing hole on starboard side.
Check transmission fluid level.
Crank engine and observe no clattering.
- DP_04.jpg (852.81 KiB) Viewed 6181 times
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C350 # 351
Lake Lanier, GA
I read Jerry Ross detailed write up on replacing the damper complete with pictures of the process.
Great presentation but the job is way beyond my pay grade.
Has anybody hired a mechanic to do this job and what was the cost ?
Punta Gorda Fl.
I have done the job several times alone. It takes about 5 hours by following the instructions posted above.
This should provide a guide for the cost for the install. Have the mechanic see the above posting before you get a quote.
The only special tools you need are an Allan wrench head socket to remove the cap bolts holding the damper plate.
The raising of the engine is straight forward. The bolt jack is the key.
The entire job was with the boat in the water.
The price for the damper plate should be about $100-$230.00 used/new plus shipping.
Please read the other posts about which damper plates can be used. If your engine/transmission was quiet at low speed before the part failure use the same OEM part ( I got mine from PYI directly)
How many hours on the engine?
Do you spend lots of hours at slow speed?
At what speed (RPM) do you cruse?
Good luck with the job
Leigh Weiss Brisa #155
Georgetown, MD. USA
Thanks for your quick reply.
I have 780 hours on the engine
very few hours at low speed
cruise at 2500-2700
I have a mechanic coming over next saturday.
He came a few years ago when I had transmission problems and told
me I had overfilled the transmission fluid.
Told me to take out some fluid and that was it.
A no charge visit.
S/V KITE, C350 #72
Habor Mobile Marine, http://harbormobilemarine.com/, replaced my damper plate. The old one looked just like the new one - no apparent deterioration. He also replaced the damper plate on Two If By Sea, a Catalina 36 on P Dock.
I ordered the damper plate from PYI and new cap screws from Torresen Marine, http://www.marinedieseldirect.com/catal ... el=M-25XPB M-35B M-40B&manufacturer=Universal&title=BELL HOUSING AND TRANSMISSION&quant_position=&catalog=201021&printparts=201021&printservice=&printoperators=&comment1=
I replaced the cap screws on advice from a friend.
Reason for having a mechanic do it is simple, after we had the gearbox replaced a bit over a year ago ( bad BAD design ) and the new PSS ( Positive Sinking System ) shaft seal installed, there was less than 1/8" between the PSS seal and the end shaft plate. I did not want to try to hoist the engine out to do the job.
Thank you very much for your posting on the damper job. Invaluable. That being said, very much not fun. I am convinced there is a sadistic side to the engineers who come up with this stuff. Upon pulling the old plate it appeared to be in pretty good shape. After being able to see how it functioned I was able to understand where and why the chattering was coming. I guess mine was in good shape because I would not let it chatter. I would either increase the RPM's or put it in neutral. The chatter seems to be occurring when, just before the plastic stretches enough that the opposing plate rest on the other plates pins, the plates are bouncinig on the pins. The new damper has horizontal springs between the plates.
My Hurth continues to fail after being rebuilt in 2011 - that's twice in four years - and option being offered is to rebuild again (at yard expense) or go for a new Hurth transmission. The latter is not an attactive option based on history.
The boat has about 40 hours on the engine since last rebuild and I run it at 2400 rpm max with original 15x 9 fixed 3 blade propeller.
The change in design of damper plate is interesting but prior to failure there was no unusual noise.
The original gearbox that we had failed at a bit over 500 hours - and it failed due to a really poor design item.
Instead of a thrust bearing, Hurth uses a thrust washer. This washer wears every time the shaft goes around. It's a guaranteed failure item. The only thing that an owner can do is change the fluid more often than spec'd. In our case, we change the gearbox lube every 100 hours. So far so good.
As for a replacement gearbox, we had conversations with two diesel motor boat mechanics who said we'd have to rebuild the engine mount because the angle required for the only box that could fit in the space was so much greater. Bottom line, as we understand it, is that we're stuck with Hurth.
I have heard from three sources that the Hurth's can fail in as little as 100 hours, and Hurth gets out of the warranty by saying it's operator error for not putting the gearbox in reverse when sailing or !!! at the dock !!! . None of blame for these failures can be placed on the damper plate.
Our advice... baby the dang thing until you sell your Catalina.
Another question I have is which damper plate to use. From what I can tell, there seems to be 3 different options:
1) the original Westerbeke 044624
2) the SACHS 1866 061 001 spring loaded style
3) the PYI high deflection 22 AA4
For those of you who have replaced the damper, which one do you use, and how long has the replacement lasted?
The Best of Times (Hull #422)
I replaced the damper plate myself and tried all three to find the best one to reduce noise at low speed (idle and below 1400 RPM).
The High Deflection damper is my top pick and have used it for about 50 hours. So far so good!
The job takes about 5 hours and from my experience can be completed in the water.
I got quite good at it after the third change!!! The instructions and pix in the above posting helped me and I made a slight variation on the bolt used to raise the engine. I also used two bolts one on each engine mount for safety. That took a little longer to jack up the engine but I felt better working alone.
Let us know if we can help and keep us posted on your progress.
Brisa Upper Chesapeake Bay
Georgetown, MD. USA
thanks in advance
Not to worry!!!, only the covers on top of the engine, the cover on top of the transmission( Under aft bunk) and the side door of the engine compartment. This will give you lots of room to do the job.
Let us know how it goes.
Upper Chesapeake Bay.
Georgetown, MD. USA
also, the first step is to remove the exhaust hose (2"). not sure HOW to remove it. I was thinking of simply cutting it off and replacing it with new hose line. Is this the method of choice?
thanks in advance.
The hose comes off by removing the clamps and twisting and pulling. I removed the hose from both the manifold and water lift for more room.
Cutting and replacing would be my last option!
If you have another snag please give a call out to the 350 community.
Leigh Weiss Brisa #155
Upper Chesapeake Bay MD
Georgetown, MD. USA
ps, I can sell you a two piece sections of used exhaust hose (can turn into a single line with duct tape) very cheap.
anyway, I was following Jerry's instructions - soooo helpful, but am wondering. If he never got the shaft flange to move backward, should i simple leave the set screws and safety wire in place and lift the rear of the engine only? or should I try to loosen the flange.
thanks so much.
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