.18 CVRM finally gave out

[Sean Bowf]

My CVRM finally failed on me. This is after about 4 gallons through it. I am VERY happy with this engine.

We were out running a couple days ago and my brother was driving, and said he had no throttle control. He was running at WOT and kept doing laps hoping to run out of fuel. As the boat burned off fuel it got lighter...and faster...and faster... It finally broke the flex shaft (with my best prop on it) and ran until it died. Tried to get to it as fast as possible, but it quit before I got there. When we got it to shore, I realized the LSN and housing had come out (which is why he had not throttle control...this held on the throttle arm), along with three other screws from the engine. Thought this was odd even with the rough ride.

Anyhow, got it all back together and went back out yesterday to see what the damage was. It was running slower than normal and I could hear a noise that sounded like a flex that needed grease...riding on its stuffing tube. Odd, since I still have my liner in my stuffing tube.

Stopped running it (was doing tuned pipe tests and only had one left to try...the cooper).

Tore the engine down this afternoon and found what is in the attached picture...the rear bearing is gone. Looks like the piston, liner, and crank all avoided damage. So might be able to get this thing going again on the price of a couple bearings.

Hind site being 20/20...I am guessing the bearing went, and caused the vibration that caused all the other screws (to include the LSN) to vibrate out.

Odd thing is...I keep hearing folks talking about the pinch on a new engine. They want to get their engine repinched to get that feeling back. Seems to take over a gallon to really loosen up a CVRM and lose that pinch...which is where it seems to run best. This engine has no pinch left and under normal conditions would push my stock Miss Vegas hull to 41-42 MPH on most days.

Anyhow...time to try to get them bearings out now...

Sean

 

[v-spec]

My CVRM finally failed on me. This is after about 4 gallons through it. I am VERY happy with this engine.
We were out running a couple days ago and my brother was driving, and said he had no throttle control. He was running at WOT and kept doing laps hoping to run out of fuel. As the boat burned off fuel it got lighter...and faster...and faster... It finally broke the flex shaft (with my best prop on it) and ran until it died. Tried to get to it as fast as possible, but it quit before I got there. When we got it to shore, I realized the LSN and housing had come out (which is why he had not throttle control...this held on the throttle arm), along with three other screws from the engine. Thought this was odd even with the rough ride.

Anyhow, got it all back together and went back out yesterday to see what the damage was. It was running slower than normal and I could hear a noise that sounded like a flex that needed grease...riding on its stuffing tube. Odd, since I still have my liner in my stuffing tube.

Stopped running it (was doing tuned pipe tests and only had one left to try...the cooper).

Tore the engine down this afternoon and found what is in the attached picture...the rear bearing is gone. Looks like the piston, liner, and crank all avoided damage. So might be able to get this thing going again on the price of a couple bearings.

Hind site being 20/20...I am guessing the bearing went, and caused the vibration that caused all the other screws (to include the LSN) to vibrate out.

Odd thing is...I keep hearing folks talking about the pinch on a new engine. They want to get their engine repinched to get that feeling back. Seems to take over a gallon to really loosen up a CVRM and lose that pinch...which is where it seems to run best. This engine has no pinch left and under normal conditions would push my stock Miss Vegas hull to 41-42 MPH on most days.

Anyhow...time to try to get them bearings out now...

Sean

Your lucky I been trying to kill my old OS 12cv in my rc car since 1999 I got a nice Lamberto Collari tuned Picco still sitting waiting since 2002 but it won't die.

 

[Dan Hydro]

Sean,

I did 7 gallons before one bearing gave up.

easy fix, your good to go.

Dan.

 

[procat]

Sean - Same thing happened to me, Replaced mine with Boca bearings ENK164HP Front 17x7x5 Rear 21x12x5 high performance bearings, so far so good , hey check your connecting rod , I spotted a hair line crack on the bottom of mine after 4 gal's

 

[Sean Bowf]

I wound up buying a new CVRX engine off Tower's scratch and dent. For now, I swapped all my parts into the new case with new bearing in it. So I am using the old P/L, crank, head, and carb. I felt like there was some play where the rod went over the crank pin, so I put the new rod onto the old piston. Still seems like a lot of play, but I guess if it was too tight no oil would get in there.

I have not run it yet, but I think I am good to go now, and have a spare P/L out of the deal. Seemed a lot cheaper than buying the bearing alone, then wind up buying a new P/L after a couple more gallons.

I will probably Ebay the excess parts (short threaded crank, air cooled head, etc, etc) to recoup a little of the money I spent on the engine, but even without that, it was cheaper to go this route.

Sean

 

[socco72]

sean mine did the same thing today at the races sounded like a shaft but it was the rear bearing also no damage to anything im replacing them with boca as well there the best i use them in my os .21 xm outboards there great.