FF 200 after 50 hours on new rebuild

[VkingMike]

We rebuilt this FF 200 after a major failure on cylinder #6 about 18 months ago for my buddy's 20ft Shadow tunnel bass boat. Two new sleeves, all machine work, all new components. Rebuilt the carbs after this failure as well, along with new fuel hoses and filters. Even cleaned out the fuel tank and added a water separator.

Well yesterday on a straight run cruising about 45-50mph, 4,000 rpm or so it lost all power and stalled out. Cranked like it lost a few cylinders so we towed it back and pulled the heads. Although I told him which spark plugs to get when he went to service the boat, the auto parts store guy insisted he knew better with his "cross reference guide" It shouldn't have had Iridium's in it, but its too late now I guess lol.

After such a thorough rebuild, my buddy is obviously devastated with the time and money lost. No damage the the cylinder walls, so its repairable but still. Obviously top two went lean, but damn... Any insight on something like this? Mixes 40:1 and it sure seemed like plenty of oil everywhere when we just pulled it apart yesterday. No Hot spots on the rods, bearings look perfect. I guess I am just trying to wrap my head around what went wrong.

[Dave Strong]

Is it a Carb motor?

Dave

[XstreamVking]

Usually when the electrode goes poof, you have either heat (from wrong plug?) or timing went too high and caused detonation. jm2cts...

[VkingMike]

Carb motor.

Timing did come to mind, maybe those two had the highest numbers.

[25two.stroke]

They do.
Looks like an overheat or too much timing or both.
I saw a 200carb run at 32deg timing for hella long.

[LakeFever]

My guesses

1. Black boxes removed?
2. Too much timing, too hot plugs
2. crappy fuel Get some BND automotive ACES fuel additive
3. Jetting to lean

[Dave Strong]

Carb motor.

Timing did come to mind, maybe those two had the highest numbers.

Some carbs have a lean spot aroung 4000rpm , the race carb 245hp motors were always rich to the point of almost 4 strokiing at that rpm to prevet lean burn down. First 225 Pro Max motors had an ECU recall for being lean at that rpm. Also water pressure and volume does a strang thing at that rpm due to poppet opening fully and the water pressure at that speed.
Check timing on all cyl and set max timing on highest cyl. Make sure carbs are real rich at that rpm, replace the poppet.

Dave

[VkingMike]

Thanks guys, I'm going to help him get it back together and back on the water.

The odd part is it ran hard and good for months on the river. Then BAM, this.

[rjdubiel]

That should be a lesson to everyone! no part throttle running! Always WOT!

[VkingMike]

That should be a lesson to everyone! no part throttle running! Always WOT!

[H2OPERF]

Those look like long reach plugs, heat range is one thing and it looks like a hot plug but also sticking the whole end of the plug into the chamber is a recipie for diaster... I would think he noticed that plug was much longer than the originals.

[VkingMike]

Well, I am standing here looking over the disassembled engine and picked up the thermostats. They are full of what appears to be debris, grass, dried mud, etc. My now thought is he ran it shallow out of the ramp and sucked up trash.

[25two.stroke]

Very possible

[Jim Speros]

Those look like long reach plugs, heat range is one thing and it looks like a hot plug but also sticking the whole end of the plug into the chamber is a recipie for diaster... I would think he noticed that plug was much longer than the originals.

Looks like it was much longer. SHould not see combustion on the threads.

And never trust an auto parts counter guy on boat stuff.

[Mrzip]

That Trash Can Do It..