So I snapped a crank in my 311 memorial day weekend !
 

Sunday of memorial day weekend I snapped my crank in the starboard motor. The boat is an 88 311 with 420 TRS. I am gonna take this as an oppurtunity to upgrade to roller cams. I was running 69.8 gps @ 4950 with my 25 pitch mirage props. Any guesses on where I will be with a little massaging... Marine Kinetics is helping me with camshaft selection. Oh.. and the new crank will be from Callies.

You should gain a couple of mph with the correct cam,intake and carb. It takes a lot to do so little.good luck.

Not really looking for overall top speed on this one, just a little more reliability. I would like to spin my 25 pitch mirages at 5200 like I use to be able to with my 23 pitch props. I think that would gain me a few. The goal is to make 1 hp per cubic inch with the roller cam upgrade.

Post a pic of the crank when you pull it. It will be interesting to see where it came apart. I come from a family of metallurgist and we are always discussing dynamic failures in castings and the causes of. This sounds like an original flaw in the casting. Spinning that engine at 5000 rpm with good lubrication and cooling with no significant vibration shouldn't have caused that failure. I'm guessing it is a cast piece as opposed to a forged unit? I would wonder about the starboard engine as well.

A roller cam with some heavier springs ad a bit more lift should give you the power to put you reliably where you want to be.

Good luck with this.

The crank snapped across the counterweight ... Clean break and no pieces in the pan. My machinist said it was due to the previous engine builder taking all the radius out of the crank when they turned it down. It was a 4340 eagle crank.

On another note ... Does anybody have any input on the stage 1 teague cams ?

Had a great weekend on the lake with the new setup. Teague stage 1 cams seem to be right on the money for these motors. Still stock bore 454 but with merlin III's in aluminum. I spun my 25's to 5100 rpm for just a second and the dream o meter was buried solid. Boat feels a little loose up on top now! I need to get a gps so I can lay down some accurate numbers.

This is now sounding better!!

For future reference...how far down was the broken crank turned?

Sprink ... I will measure the crank up when I get a chance but I am pretty sure my machinist told me it was only .010".

I'f 454Captiva's doesn't work out let me know. I have a 4340 crank turned .010 with new rods and bearing I'd like to make somebody a deal on to get it out of my hair.

Snapped Crank

Another

This was the nerve racking part coming out of the boat!

WTF! Who does this?

Port engine still in the boat. This is the point at which I realized the heads were phucked. Hey, atleast it had the correct rocker arms!

New heads on port engine! Bling!

Starboard engine back from machinist sporting a new internally balance Callies crank. Degreeing in Teague Stage I Billet Roller Cam.

I just really like this picture ...

Ready to drop back in. Took me a whole Sunday to finish assembly with trans and offshore mounts. Was a pita getting it out with the accessories on so I left them off going back in. Way easier!

This is the point at which I took a big sigh of relief! While the Starboard engine was out I cleaned the bilge, tidied up some wiring, and added through hull flush kits since I am running TRS.

Intakes on, really wanted a set of Darts, maybe winter project....

In this pic I am just showing how I replaced the 2' section of 4" exhaust hose with 4" S.S. pipe. I think it looks better, Won't burn up either!

Done!... And now I can bury the speedo!

In this pic you can see where I placed the through hull fittings for flush kits. They are just above each transom assembly through one of the holes that held the old silent thunder platform on.

How bout now

AWESOME JOB TYLER!!!!!:bunnydance:

Thanks Jeremy!

Before you broke the crank, what kind of improvements had you done to your 420's? Your GPS speeds with TRS's and 420's seem very fast for fresh water.

When I bought the boat five years ago it was a turd! First year went through two motors on the right side, warranty covered both times. While going through this I went to the imco exhaust. The first winter project I tackled was getting rid of the silent thunder for the aluminum platform. Kinda funny, the boat would run exact same speed gps with 23's as it would with 25's. 69.8 mph light on fuel, and just two people.

If I was closer to a lab I would love to get that piece under an electron microscope. Something went wrong with this forging when it was in the mold. Could have been a bad metallurgical mix...maybe it was mishandled prior to annealing or some other process. I doubt seriously that this was due to abuse or extreme use/shock...properly forged pieces don't fail like this did. My take is this is a result of compromised QC at the mill.

My machinist pointed out that this crank was turned down .010" when they turned it down they didn't build the radius back in it at all. He said the bearing fit was very poor also. My guess is it was a used crank and somebody slammed it together without checking anything! You can feel the edge of the stock radius with your finger, actually you can see it !

Did this boat come from Gibbs? If so, when he had it he had one of the motors out sitting on the shop floor. That would expain a lot...

I went through two motors on the starboard side the first season I had the boat, same side with snapped crank this season. Jeff didn't build that motor. He did warranty it though and let me use their 31 imp for the season while mine was down. This boat has had numerous new cams replaced throughout it's life. The trail of receipts that came with the boat tell the story, it's quite something.

Looking good now.

Port starter went out so I took a little video clip last night after I got the new permanent mag hi-torque version installed.

Let Bob Madara do the cam and top end .....

I did talk with Bob about the cam kits but timing was going to be an issue. I went with the teagues because he had everything I needed in stock. I was really impressed with the quality of the cams from teague, they were the copper coated cores custom ground by andrews. Hindsight being 20/20 looking back on the project, it was really nice when working on the boat at 7 or 8 pm CST and being able to call the guys at Teague for technical questions. You just never know what you are going to encounter on a project like this.

Awesome Job..I recently purchased a 311 with the same power package 420 with TRS..she is a work in progress as well but seeing what you have done and dealt with has motivated me to keep plugging away and with some time money and sweat Ill be where you are in a few years! Ill be using some of your suggestions in here since I just want to squeeze a little more out of my engines when I pull them not punch them out..you mentioned putting in a flush kit because you have TRS drives..Im curious as to why when you run in freshwater..Im going to lose the silent thunder platform this winter as well and put on the tube aluminum like you have and go to true thru hull exhaust..great thread..I love to see engines in pieces and then come back to life..excellent work

You will love the sound after ditching the silent thunder platform! The only reason for the flush kit was so I can run the boat on the hose in the driveway. I can now just simply hook my garden hose adapter onto the transom and fire away, before I had to unhook the hose from the strainers and shove a garden hose down it ... what a pain in the A$$.

Any ideas on what color I should do the intakes in? I am going with the brass lined Merlin III's. I was thinking the reflective chrome powder.