97 Speedster twin 717 break in procedure?

[Robert Juliano]

I installed 2 new SBT premium engines, new carburetors, new oil lines, primed oil pumps, new fuel filters, added break in oil to fuel. I warmed up engines, then started 1st phase of break in never going over quater throttle never leaving throttle in one position. after 15 minutes I let it cool down. I then started to do another 15 minutes to use 1/2 of fuel in tank, I noticed a metalic ticking noise in one engine. I couldn't tell what the noise was coming from I was alone in boat. I preceded to break in and the engine that was making ticking noise engine blew up. I pulled spark plugs out and mag side plug was smashed. PTO plug was ok. I then pulled head and mag side piston looked to me like a lean melted piston. SBT sent me new engine, I had to replace rotary valve and oil injection cover due to damage when engine blew up. I installed new engine double checking all my work hoping I didnt do something wrong. I started both engines in my driveway to see if they would start and idle @ 3k RPM before putting in water. All ok so far. My question is what is proper break in procedure? Is it by time or gallons of fuel used. I have seen nothing anywhere for twin engine 717 speedster. I only see for single engine PWC. Any info would be appreciated.

 

[Robert Juliano]

Here are pics of failed engine.

 

[burtshaver2021]

See what others think but I’m guessing that the one cylinder ran lean, when you say replace ed the fuel filters, do you mean inline aftermarket fuel filters? I’m pretty sure my 98 Challenger has the same fuel filter/water seperator as all the pwc. Where did you get the new carb from? And did you verify the jetting and settings? I’m guessing lean, either not enough fuel or too much air.

 

[mikidymac]

That is mechanical failure.
Could have run lean but could have also been typical SBT quality....
You should not have pulled the head as sometimes they won't honor the warranty but you need to get them into the warranty process asap.

With any new engine always, always service the carbs with all new genuine Mikuni parts as that is 99% of what causes engines to fail in the first place.

Here is the Break In procedure....

Ok, first half tank don’t go over 1/4 throttle but get it up on plane, you don’t want the engine under a heavy load.
And always vary the throttle the entire time, never hold it in one spot for any length of time.
Next half tank don’t go over half throttle and vary the throttle. All on premix and oil injection.

Also give it time to cool off every 15 minutes to heat cycle the engine.

The next full tank is only raw fuel with oil injection. Half tank at 3/4 throttle and varying the throttle. The last half tank you can go full throttle but don’t hold it wide open.

And you are done.

Seadoo OEM rings don’t have Teflon coating like the Japanese ones so depending on what you used they can take longer to seat.

 

[Robert Juliano]

I installed stock fuel filters with new inserts. I ordered stock replacement mikuni carbs for 717 engine's. I turned low out 1 and 1/4 turns and high closed per seadoo specs. I did put aftermarket spark arrestors, my guess was too much air leaning it out. I installed OEM air / spark arrestors back on.

See what others think but I’m guessing that the one cylinder ran lean, when you say replace ed the fuel filters, do you mean inline aftermarket fuel filters? I’m pretty sure my 98 Challenger has the same fuel filter/water seperator as all the pwc. Where did you get the new carb from? And did you verify the jetting and settings? I’m guessing lean, either not enough fuel or too much air.

I installed stock fuel filters inserts. I ordered stock replacement mikuni carbs for 717 engine's. I turned low out 1 and 1/4 turns and high closed per seadoo specs. I did put aftermarket spark arrestors, my guess was too much air leaning it out. I installed OEM air / spark arrestors back to original.

 

[Robert Juliano]

I installed stock fuel filters with new inserts. I ordered stock replacement mikuni carbs for 717 engine's. I turned low out 1 and 1/4 turns and high closed per seadoo specs. I did put aftermarket spark arrestors, my guess was too much air leaning it out. I installed OEM air / spark arrestors back on.

 

[mikidymac]

You need to run the stock air filter or it will absolutely run too lean.
You also need to check the jetting, needle and seat and springs in those new carbs to make sure they are jetted correctly for you model. Don't assume box new carbs will be jetted correctly.