Hey, im Justin just purchased an 02 black thunder 46 ec with twin merc 500 efi’s with about 160 hours on them. I am looking for any information I can get on these motors and or black thunders as this is my first one. Specifically I have heard that the valve springs should be changed and am curious what manufacturer makes the best kit for this. Any information would be greatly appreciated. It will have a long time to tinker with her till warm weather hits again looking forward to hitting the water next year.

The carbed HP500's were the ones with the premature valve spring failures. They used Crane springs and the inner springs were the ones that broke. The 500EFI's used Comp Cam 929-16 springs that had much better life.

Welcome. Checkout the Black Thunder forum on here also. As far as your 500efi ???'s, others that know more than me will chime in and help. Again, welcome to OSO

Chris

You shouldn't need to do anything to the 500efi's other than change the oil until about 250hrs. Then its about time for a leak down test to check the health of the valves and maybe a valve job, head gaskets and springs in the 250-300hr range.

My 250 Hr HP500EFI had 3 broken inner springs out of two motors.

I replaced them during last winter when I had to replace drive couplers. Not a hard job.

Cut open the oil filters ck for metal..do a leak down, if its ok and the previous owner took care of it ,Run it.

if ya have extra money,put the 929's in it,if ya pull the motors plate hone,rings. bearings,head job,put the felpro head gaskets in it.

hey post some pick of ya new ride
Rob

Welcome to ihe BT family. Going to pull my 500s out this week for inspection and couplings.
Bob

Is this the red one that has the Black Thunder logo on the sides? Been in that boat a couple times and my mechanic up in Lake George, NY serviced it. Talk about a condo on water!

First congrats on your new ride, you got a flying condo that can take the whole party on it

46 BT, be easy on your drives, that will be your weakest link on your set up, probably XZ or XR's.

500efi's Valve Springs are weak in them but not until 250 hours or so. I pulled mine at 320 and already had 2 inner springs broken. Replaced with Isky springs but I cannot remember the #'s. Not a big job at all, local mechanic should be able to do it for you.

thanks for the information it is very heplfull. I will post some pics as soon as it gets back from the detailer she was prety filthy. I am also looking for someone in my area to get paint fixed it must have sat in the water and the paint is bubbled at water line. I know mitcher t does alot of BTs but he is a good hall from milwaukee