250xs looses power at 4000 rpm

[lucas16d]

2006 mercury 250xs 1E001460

I've had my motor at the mechanic and it did not throw any codes on the computer and it appears to idle fine. It seems like its slightly down on power during holeshot, mid range feels close to normal, however once it gets around 4,000 rpms it feels like it falls flat on its face. the power just cuts out and I have to really trim the motor to get it to touch 5000. it has new plugs, reeds and I had the fuel rails cleaned. however I am not too sure how well I trust that the guy that cleaned them did a good job. never received any data showing how they performed. mechanic is thinking I should send off rails to his guy to get tested and cleaned. anyone have any ideas what else could be causing this issue? motor only has 110 hours.

thank you!

[lpugh]

First verify full throttle at the throttle valve
Scan computer codes and freeze frame data
check available voltage to spark plugs
compression test
Drain vst to check for water and test alcohol content
check fuel/air pressure while under load including low pressure
Be sure the compressor belt is good and no slipping

[Jtreed99]

Start with the stickies: http://www.bbcboards.net/showthread.php?t=22490

[lucas16d]

All the fuel lines have been replaced, when I got the boat back from the mechanic I told him what it was doing and the throttle was the first thing he checked. He printed off the freeze frame codes and they did t show anything. Compression test was good but he said he’s going to do another one to double check. We both drained the vst but didn’t check alcohol content. The boat has two different tanks and I hardly ever fill them both up at the same time. So each tank has gas from a different station in it. Runs the same off both tanks. We hadn’t check the pressures while under load, just idling. And the belt appeared to be good. When I changed spark plugs myself after getting it back from him I forgot to put one plug wire back one. Hole shot was slow like it was on five cylinders, and topped out around 5k. Caught the loose wire, hooked it back up, hole shot was there along with mid range acceleration, but it still feels like it’s hitting a wall at 4K and tops at 5k.

[JOE54]

checked for broke reed or turned sleeve ???????? hmmmmm

[Savage]

+100 to EVERYTHING in post #2..... especially All the pressure tests.

[Savage]

And....post #5. Was motor overheated?

[lucas16d]

I saw another thread about a turned sleeve, spoke with mechanic about it and he said its possible for the sleeve to be turned but the motor hadn't been hot enough to really worry about it. he was gonna check them when he pulls the rails off. I replaced the reeds first when all this started, original reeds where carbon fiber and looked fine. I put a set of ccm reeds in it but there wasn't a difference in performance.

[EuropeanAM]

I strongly recommend Carbon Fiber reeds for the race model (and ProXS 225/250) engines.

In addition to the above VERY GOOD info that's been provided, here's a SIMPLE, and often over-looked item:

Get an INCH POUND (lbs/in) Torque Wrench. Set it to 75 lbs/in.

Insert it into the belt tensioner 3/8" square, and pull the wrench to relieve the belt tension. Does the wrench "click" BEFORE the tensioner reaches the end of it's travel???

Seeing a LOT of engines lately with springs that no longer keep the belt tight enough to support full-throttle operation.

[lucas16d]

I will check on that. Thank you! What’s the difference from the carbon fiber and the fiberglass reeds? I had just seen good reviews for ccm so i went with them.

[EuropeanAM]

CF are harder (overall), and overall are quite durable. The OEM CF reeds were a very high-quality reed (hard to make anything "better", other than perhaps being less costly).

Are the reed blocks still rubber-coated?

[lucas16d]

Yes they are, the only thing I replaced was the reeds themselves

[lucas16d]

well upon pulling heads #1 and 2 sleeves where turned. thank y'all for the help. looks like she's gonna be off to the machine shop.

[DewRonInc]

When sleeve turns do sleeves have to be replaced or what?

[Savage]

Depends on the condition of the sleeve.

[JOE54]

^^^^^^+1

[Rip Bass]

What would cause two sleeves turn? Those are in there pretty tight.

[lpugh]

Overheating, or improper installation

[lucas16d]

its the top sleeve on both sides of the engine, I was having overheating issues from wood stuck in thermostats, granted I never saw the smart craft gauge over 150 degrees. mechanic said its $250 a sleeve for a machine shop to put new ones in. so thats almost a no brainer. other than new rings and a rebuild kit, does anyone know of anything else that should be checked or replaced while its all torn apart? engine has 120 hours on it.

[silvertalon]

$250 should be just the cost of the sleeve. All said and done, $400 per hole is the norm. Expensive stuff!