250 ProXS Tuner

[clayc]

A year ago I bought a 2013 Triton 21HP w/ 250 ProXS 2s. Long story short, performance was off and finally located a chunk of flat metal in the lower units exhaust passage. The chunk of flat metal was the tuner or more specific the can in the midsection. What I learned was Merc went from an open can (on early Opti ProXS’s) to one with a divider plate that ran the length of the can to just above the lower. The problem is the last 4-5” isn’t supported and in time can break off and lodge in the lower, restricting exhaust.

From my understanding, the open vs divided require different “ECU” tunes due to the open design “scuffing” exhaust. Which tells me (the open design) requires a richer fuel ratio. And maybe that’s when the 250’s ran a bit stronger.

I’ve been running engine with the broken divider (remember, it’s the bottom 3-4’). I now have a new can with divider, just haven’t pulled powerhead to replace it.

The past two owners said my rig would run in mid-upper 70’s w/ a tournament load. Which it will not… And I’m only seeing about 5650 rpm w/. a B&B 25p Tempest, on a medium-lite load. And I have the prop both said it would run that speed with and have tried two others as well. And my set-up it right, so I’m looking at engine. Engine compression #’s are good as is the fuel and air pressure’s.

Question #1. Do you think losing the last bit of divider would kill the upper end power? (Or maybe overall power)?

Question #2. Have any of you encountered this and what was the performance change?

[XstreamVking]

I would start with a compression check and leak down. It passes then go ahead and fix the known issue. Also check that the engine is getting full throttle at the throttle body. Also there is a roller on the linkage that can wear and cause problems. Performance issues can be tuff to diagnose

[clayc]

Compression:
1) 120
2) 124
3). 120
4) 124
5) 122
6) 120

Leak Down on all 6 is 1-2%

buuuttt,, turning air pump by hand,,, gotta rattle.. and I hit a spot during compression and it has a “grinding” feel and a pop as it rolls thru… dammit

[clayc]

I’d post a video of rolling air pump by hand, but I don’t know how!

[XstreamVking]

Compression looks good change the tuner and hopefully you will find an obstruction the compressor is is usually good for 800 hrs as long as it’s not sloppy and makes pressure it’s ok. You can use soapy water on the fittings and hoses to check for leaks. How about the injectors?

[clayc]

Used soapy water a month ago to find a leaking air hose. At that time I had gauges on the air / fuel / and low pressure fuel,, all were well within spec.

Engine was running w/o any miss or other issues other than what I described in original post. What’s your opinion on pulling injectors and sending off for cleaning since I found this compressor issue? Any suggestions on where to send them or it is something I can do on a bench?

[clayc]

Update: Removed and opened compressor…. Only problem I found was the roller bearings in the connecting rod are shot. They are rough.. there was a little bit of glitter in there, but not much..

[clayc]

Rod journal on crank is damaged too.. new compressor time. Thanks for the input! I’ll update the performance issues after I get compressor replaced and injectors flushed

[clayc]

Since this post I made another post about direct injectors. Long story short, changed compressor and sent injectors for clean n flow tests, 5 were failed. After lots of research, reinstalled and running them as is. Same performance as it was prior to compressor failure.

Circling back to original post above,,, everything mentioned has been checked / verified. The “can” with divider has not been replaced yet. That’s next on list. Does anyone have an opinion on performance change with that divider missing the last 4-5”?

And, do you all know the acceptable “spark gap” would be from the ignition coils, measured with a spark gap tester. (I know I read it somewhere but can’t find it)

[clayc]

Well,,, new tuner installed and lake tested.. didn’t see much difference. 74.5 mph @5800…. 3/4 tank, empty wells, all gear! 71.5 at 5700 w/ full wells and into a headwind. Oh,, temp was 89 deg

[MrG]

Should cut the tuner at the mid glue joint like the 300 did this to the new 250XS opti from Merc I paid 6 k for each dressed powerhead had 225 opti’s 2002 with 3000 hrs were getting piston slap !! Now they run strong Ang push the 32 contender with TTop to 60 mph