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Rabbit hole

Nov 18, 2010
2,370
Catalina 310 Hingham, MA
I dont understand the idling issue and how it can affect the damper. with the trans in neutral and the engine at idle, there can't be a lot of forces being imparted into the damper itself. its bolted to the flywheel and has a free spooling trans.. there's zero load. i can see where if you go in and out of gear and higher than idle RPMs will cause the damage... which i believe is one of the main purposes of the damper.. to dampen the slam of in and out of gear.. considering the impact of that, vs a free spooling transmission, i can't imagine idle is causing damage.. unless your idle is rocking the boat its so rough..
Old dampener plate
IMG_0906.JPG

Pile of pieces of the plastic ribon
IMG_0905.JPG

How much was actually left holding the plate together
IMG_0959-1.JPG

New dampener plate
IMG_0907.JPG
 
Apr 5, 2009
1,078
Catalina '88 C30 tr/bs Oak Harbor, WA
I dont understand the idling issue and how it can affect the damper. with the trans in neutral and the engine at idle, there can't be a lot of forces being imparted into the damper itself. its bolted to the flywheel and has a free spooling trans.. there's zero load. i can see where if you go in and out of gear and higher than idle RPMs will cause the damage... which i believe is one of the main purposes of the damper.. to dampen the slam of in and out of gear.. considering the impact of that, vs a free spooling transmission, i can't imagine idle is causing damage.. unless your idle is rocking the boat its so rough..
Damage done at idle is a possible theory for damage seen in these posts based on some loose forensics.

I am not positive if idling is harder on the damper plate than under power but have read many posts saying that the rattle is loudest at idle. The rattle would translate to impact which is most likely what causes the wear to the spline and output shaft. It takes a lot of constant force to deform metal but a hammer can get the job done with a fraction of the applied force.

At idle, with no load, the slow turning 3-cylinder engine with light-weight flywheel will not run at a constant rpm but will have turn in a series of micro accelerations every 2/3 of a revolution. The damper and transmission have their own rotational inertia and will want to spin at a more constant rpm. This difference without much load, will allow the splines to pound between thrust and retard side of the lands and hammer out the metal. The more wear you get the greater the hammering.
The spring type damper will have the ability to ease the hammering while still having the require torque capacity.
Just my theory but makes since in my own mind :huh::eek:
 
Dec 25, 2008
1,566
catalina 310 Elk River
I dont understand the idling issue and how it can affect the damper. with the trans in neutral and the engine at idle, there can't be a lot of forces being imparted into the damper itself. its bolted to the flywheel and has a free spooling trans.. there's zero load. i can see where if you go in and out of gear and higher than idle RPMs will cause the damage... which i believe is one of the main purposes of the damper.. to dampen the slam of in and out of gear.. considering the impact of that, vs a free spooling transmission, i can't imagine idle is causing damage.. unless your idle is rocking the boat its so rough..
The purpose of the damper plate has nothing to do with going into gear, it is not a clutch. The problem is that with a low cylinder count light flywheel engines creates excessive torsional vibration. Each time a cylinder fires the crankshaft accelerates then slows down until the next, fewer cylinders more time to accelerate and decelerate. This torsional vibration is tough on trannys, so the damper plate smooths out the variations in crank speed. The faster you run the engine the more momentum is stored in the flywheel so the damper does not get articulated as much. But at idle, it gets worked pretty hard.
 
Dec 25, 2008
1,566
catalina 310 Elk River
My engine is the M25XP with a Hurth Z50 and my understanding is that it has the spring type damper plate.
They started using the R&R dampers (poly ribbons) around 2000 so it is unlikely you would have one. This was a bad idea as the polyethylene eventually hardens and breaks. The spring dampers last longer but, wear the contact point between the springs and the disks. Eventually the springs fall out or break.
 

BillyK

.
Jan 24, 2010
470
Catalina 310 Ocean City, NJ
The purpose of the damper plate has nothing to do with going into gear, it is not a clutch.
I agree with you and wasnt trying to imply that it was. My thoughts are just that going into gear is one of the most impactful events of the entire drive line. you are taking all of the mass of the prop, the shaft and the transmission and connecting it to the engine spinning at 1000rpm instantly. The clutches i'm sure absorb some of that by feathering the spinning engine and the non spinning gear together slightly.. however, there is still a major force to be dealt with by the springs in the damper. There's a reason they mostly fail when you go into gear and not while you are already in gear. its because of that rotational force impacting the system. take something going 0 RPM and make it go 1000RPM in under 1 second. That force has to be absorbed somewhere and the only point in the system that i see is the damper plate.
 
Apr 5, 2009
1,078
Catalina '88 C30 tr/bs Oak Harbor, WA
I agree with you and wasnt trying to imply that it was. My thoughts are just that going into gear is one of the most impactful events of the entire drive line. you are taking all of the mass of the prop, the shaft and the transmission and connecting it to the engine spinning at 1000rpm instantly. The clutches i'm sure absorb some of that by feathering the spinning engine and the non spinning gear together slightly.. however, there is still a major force to be dealt with by the springs in the damper. There's a reason they mostly fail when you go into gear and not while you are already in gear. its because of that rotational force impacting the system. take something going 0 RPM and make it go 1000RPM in under 1 second. That force has to be absorbed somewhere and the only point in the system that i see is the damper plate.
This is true but the damper is made to handle these loads. It is the micro hammering that does the damage to the spline and output shaft. Have you ever used a palm nailer? They use a hardened steel pin that is the diameter of a 16d nail and are a couple of inches long. That little pin hits the head of a nail 2,000 to 3,000 times per minute and will sink a 20d nail into hardwood with only a small vibration felt by the hand. It is the little tap of the engine on the free spinning input shaft of the tranny in neutral that do the spline damage.
 
Dec 25, 2008
1,566
catalina 310 Elk River
I agree with you and wasnt trying to imply that it was. My thoughts are just that going into gear is one of the most impactful events of the entire drive line. you are taking all of the mass of the prop, the shaft and the transmission and connecting it to the engine spinning at 1000rpm instantly. The clutches i'm sure absorb some of that by feathering the spinning engine and the non spinning gear together slightly.. however, there is still a major force to be dealt with by the springs in the damper. There's a reason they mostly fail when you go into gear and not while you are already in gear. its because of that rotational force impacting the system. take something going 0 RPM and make it go 1000RPM in under 1 second. That force has to be absorbed somewhere and the only point in the system that i see is the damper plate.
Yea, it will flex going into gear for sure, but that happens infrequently compared to 3000 times a minute while idling and it is not an impact hit as the clutches in the tranny will be slipping initially. Once there is just a little play in the interface between the input spline on the tranny and the damper plate collar that hammering action starts to beat it up. So when replacing the damper that interface need to be spot on. Mine was worn like JKs, but I used a softer damper plate mounted to a custom made ring which pushed the collar further towards the bearing of the tranny to a spot that was not worn.
Input shaft wear.jpg
New Damper Plate Assembly side view.JPG
New Damper Plate Assembly top view.JPG
 
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Likes: Hayden Watson

BillyK

.
Jan 24, 2010
470
Catalina 310 Ocean City, NJ
Successfully fired the engine today after replacing the entire fuel system. The engine really is self bleeding. i filled the two filters with diesel, opened up the valves on the tank and turned the key to run.. i could hear the lift pump clicking away and blowing bubbles out of the return line in the tank.. i let it run like that for 10 minutes. After which i hit the glow plugs for 15 seconds and pushed start.. the engine fired immediately and idled for 2 minutes. i did coat the raw water impeller with some Vaseline so it wouldn't melt.

the new engine mounts also made a tremendous difference on the shake at idle.. and the new damper plate was also much quieter as well.. so far so good!
 
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Likes: DaveJ and JRT
Dec 25, 2008
1,566
catalina 310 Elk River
Glad you have things in better shape now. Just curious what was the condition of your input shaft of the tranny?
 
Apr 5, 2009
1,078
Catalina '88 C30 tr/bs Oak Harbor, WA
Successfully fired the engine today after replacing the entire fuel system. The engine really is self bleeding. i filled the two filters with diesel, opened up the valves on the tank and turned the key to run.. i could hear the lift pump clicking away and blowing bubbles out of the return line in the tank.. i let it run like that for 10 minutes. After which i hit the glow plugs for 15 seconds and pushed start.. the engine fired immediately and idled for 2 minutes. i did coat the raw water impeller with some Vaseline so it wouldn't melt.

the new engine mounts also made a tremendous difference on the shake at idle.. and the new damper plate was also much quieter as well.. so far so good!
I don't even fill the filters. I just rub a bit of diesel from the old filter on the o-ring and let the lift pump do the rest. Much less chance of spilling. I let it run until I hear the pump bog down which indicates that the system if full. When you close the thumb screw, the pump should slow down almost immediately to the normal approximate one tick per second. If it takes longer than that to slow down. open the thumb screw for a bit more time.
 

BillyK

.
Jan 24, 2010
470
Catalina 310 Ocean City, NJ
Glad you have things in better shape now. Just curious what was the condition of your input shaft of the tranny?
I had to replace the input shaft on the trans.. luckily there was a bloke on the boards here that had a trans that he no longer needed and sold it to me. So the trans got rebuilt with the new input shaft and a box of spare trans parts in the basement now.

Bad shaft
IMG-3789.jpg


Good shaft
IMG-3863.JPG


The title of this thread is very appropriate.. this boat has truly been a rabbit hole. Everything i repaired uncovered 2 or more other things that were needing attention. This past weekend i had to replace the hose the went from the raw water pump to the heat exchanger.. it is routed between the alternator and the block, goes past the starter and under wires and then over the engine mount and into the exchanger. i'm calling this satan's hose.. i had to remove the alternator and the face of the damn sherwood pump again to get this hose routed. a 2 foot hose took 3 hours to replace correctly. i have a problem with perfectionism so some of that time is on me making sure its perfectly routed.
 

BillyK

.
Jan 24, 2010
470
Catalina 310 Ocean City, NJ
I don't even fill the filters. I just rub a bit of diesel from the old filter on the o-ring and let the lift pump do the rest. Much less chance of spilling. I let it run until I hear the pump bog down which indicates that the system if full. When you close the thumb screw, the pump should slow down almost immediately to the normal approximate one tick per second. If it takes longer than that to slow down. open the thumb screw for a bit more time.
thumb screw? where's that and what does it do?
 
Apr 5, 2009
1,078
Catalina '88 C30 tr/bs Oak Harbor, WA
the M25xpb is self-bleeding, so there is no need to open a bleeder valve.
I know nothing about the XPB so my comments are only related to the XP engine. In my documentation, it says that the XP is self-bleeding so there is no need to use a wrench to open the injector lines to get the fuel up to the injectors. It does say that to fill the filters and remove the air from the fuel lines and system, the bleeder valve should be opened with the lift pump running which circulates the fuel through the system and returns it to the tank. When the pump speed slows down, close the bleeder valve which will slow the pump to once per second and start the engine.
 
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Likes: Tom J
Sep 29, 2008
1,783
Catalina 310 #185 Quantico
I will say cracking open the bleed bolts on the spin on filter and by the injector pump do help speed things up.

On a related subject how are folks finding that replacement transmission working out? My original transmission is working fine, but always good to know about new options.
 
Apr 5, 2009
1,078
Catalina '88 C30 tr/bs Oak Harbor, WA
I have a friend who installed one last year and he has not had any problems with it. One thing that I found out from him is that the HWB 50's usually fail by loosing the friction disks for the forward gear only. I have heard from more than one person who needed to back to a harbor after losing forward. His went out just before a long planned cruise and he didn't want to miss his opportunity "just because the tranny didn't work in forward." He bought and installed a second-hand left-hand prop and went on his cruise. He just needed to remember to shift into reverse to motor and left it in neutral when sailing.
I may need to see if he wants to unload his backwards prop. :biggrin: