Transmission Failure

[csuggs]

I'm back in the repair column, this time with a broken transmission. We went out last night for a short session, the boat started fine and we went up the river about 300 yards to warm-up the motor. My oldest son jumped in with the wakeboard, and when I hit the throttle to pull him up, BAM! The trans broke and motor rev'd . . . then I had to get towed back to the ramp by a 1988 Mastercraft. At least we weren't too far from the dock and ramp.
The damper plate has been making noise for the past month, ever since we had a boat full of teenage boys, trying to pull up some inexperienced riders. I was hoping to put off any transmission repairs until after the season was over, but so much for that. I will try to disassemble the trans tomorrow so I can order parts on Monday. By the way, I told my son he needed to loose some weight! (He's actually very fit, but I couldn't resist the opportunity!)

Anybody know if this problem sounds damper plate related or am I going to get into more - like gears, etc?

[Supra-in-steamboat]

Ouch. Sorry to hear. What noise led you to thinking it was the damper plate? Did it offer any other symptoms other than a noise- ie. slip, vibration, grind? Hope all goes well with your disassembly.

[csuggs]

Here's my question for anyone that may know the answer: Will a faulty damper plate necessary cause an actual failure in the velvet drive, or could my problem simply be that the damper failed and is the broken link in the driveline? I know the damper plate was getting worn because I experienced the rattling noise from the bell housing at idle for about 6 weeks now.

[fastab]

The tranny should be a sealed unit but, the dampner plate will have to bolt up to the input for the tranny. Depending on what is wrong in there it could take out the input which would mean tranny would have to come apart

[csuggs]

Pulled the trans out today, along with the dampner plate and flywheel. The dampner plate is obviously damaged, but I think that it is transmitting power to the input shaft on the tranny so I'm guessing the failure is internal. Unless someone knows a fool proof method to be sure the trans is good, I will ship it out to someone this week. Any recommendations? I removed the flywheel becuase it has some worn teeth so I will take it to a machine shop for repair.

[Blackntan90]

I dont really know what to say... very sad indeed! Well it does appear that you have things well at hand! But I am a little surprised that you did not wrap the entire boat like you did the floor!! The interior detail looks awesome! Best of luck, and keep us updated!

[csuggs]

Got two opinions this morning from Jim at Viper and Chris at Hale Marine in Viriginia (Velvet Drive Service Center). Both say they think my problem is a simple damper plate failure so I ordered parts this morning.
Damper Plate from Hale Marine $61
Replacement shaft seal bellows from Lasdrop $120
XPC strut bearings from skidim $60

In addition I have a new prop shaft and coupling that I will install, as well as a newly refurbished 4-blade prop. Hopefully I'll be back in the water this weekend!

[87SunSportMikeyD]

Clint I was diagnosed with a failed damper plate too. Kudos for doing it yourself. My mechanic said mine was old and springs were worn so he is replacing it, but it was not broken and not the source of my problems. Have you had your boat compression tested? Very simple and cheap once you get the trans hooked back up. Best wishes.

[csuggs]

No compression test. Should I? Was your problem somehow connected to the motor?

[87SunSportMikeyD]

Well... the symptom was a knocking noise. Good mechanic took a ride on the boat and listened to the engine with a mechanics stethoscope. He said he thought it was transmission damper plate but he also heard some engine noise. Personally we think he was just incorrect.

I took the boat to a different mechanic who took it apart and said the damper plate was worn and springs loose, but not breaking or broken. So while I was messing around trying to figure out what the problem was, a compression test would have identified it right away, in my case anyways.

We are suspecting a thrown rod or failed main bearing. My problem is still technically unidentified because we decided to get a new engine rather than spend lots to have him tear it down and then have it rebuilt. We got a newly rebuilt 351w longblock from craigslist for $950. We get to keep our engine so we will have it rebuilt eventually and maybe resell it or something.

I also got the damper plate replaced because the mechanic recommended it, along with a whole new distributor and starter.

Naturally, my problem is likely not the same as yours. I have heard at least 3-4 people with SunSports in our age bracket describing similar symptoms, a knock only under load at higher rpms. Best wishes.