250 XS runs good up to around 4000 rpm and tops out @ 5000rpm

[topwater1956]

2004 TR21 Triton 250 XS---ser. # 0T818359---idle, hole shot and acceleration is normal to around 4000 rpm then slowly pulls to 5000 rpm. Tested coils while wot, all firing good, fuel pressure 115psi,
air pressure 105psi, boost pump 30psi, compression 118-120 on all, spark plugs look great. The motor has 521hrs total and rebuilt by mercury @ 452 hrs.
so has 69hrs. The man I got it from had it 8 years and thought 5000rpm @ wot was normal.
The run history on the DDT shows the motor has never been more than 5000rpm. No codes and I sent the PCM to Simon to get tested. Tested good and no code history.
Changed PCM from a good running 250xs and it ran the same. Motor is smooth as a sewing machine, but is real lazy after 4000 rpm up to 5000rpm tops.
I sold the exact boat and motor combination about 4 months ago and it would tack 6100rpm with same setup.

Any help would be greatly appreciated.

[Savage]

Put on a smaller pitch prop, as a test, and see if RPM increases. What prop is currently on the boat?

[lpugh]

What is the top speed at max RPM and what prop is on it
Check fuel pressure while problems is occurring, check to be sure it is getting wide open throttle, verify TPS and Maps sensors are within proper range.

[topwater1956]

I did and it was still lazy from 4000 up. It gained 200rpm. From a 27trophy down to a 26 Tempest.

[topwater1956]

The fuel pressure, air pressure, TPS, map are all within range @ wot

[Basshead35]

I have a 2007 Mercury Pro XS 250 on a Blazer 202 Pro V. The engine would drop out at WOT several hundred RPM. No warnings or codes. Sent my injectors and fuel rail assembly in to Don at European Marine. Don stated I had 3 bad air injectors. I replaced the fuel rail, air injectors, and he cleaned and tested the fuel injectors. Motor does not drop out and runs like new. 5900 RPM with a 27p fury.

[Savage]

I did and it was still lazy from 4000 up. It gained 200rpm. From a 27trophy down to a 26 Tempest.

27P Trophy is TOO high of a pitch for that boat and motor combination.

[EuropeanAM]

27P Trophy is TOO high of a pitch for that boat and motor combination.

100% agree.

Also suspect you're using an ANALOG tach (which is not going to be very accurate).

Additionally, the provided air and fuel pressures indicate a PROBLEM. Recheck, verify, and swap gauges to triple check readings, then report back.

[topwater1956]

27P Trophy is TOO high of a pitch for that boat and motor combination.

I'm going to have to disagree with you on the prop. I currently own 2-TR21 Tritons 2004 and 2005 with 250XS motors and owned a different one
a couple of years ago and all 3 of these boats I set up the same. The other 2 would turn this 27 Trophy 6000-6100 and
this one will only turn it 5000 @ 60mph GPS. The other 2 boats would GPS 78 mph with same load. I did try a 26 Tempest and gained 200 rpm.

[Savage]

I'm going to have to disagree with you on the prop. I currently own 2-TR21 Tritons 2004 and 2005 with 250XS motors and owned a different one
a couple of years ago and all 3 of these boats I set up the same. The other 2 would turn this 27 Trophy 6000-6100 and
this one will only turn it 5000 @ 60mph GPS. The other 2 boats would GPS 78 mph with same load. I did try a 26 Tempest and gained 200 rpm.

And I'll disagree with your reported RPM'S from an analog tach using a 27P Trophy.

I own a TR-21 as well with a 250 HP, that runs over 80, and have tested and used every Mercury prop made, while dialing in my setup....

[topwater1956]

And I'll disagree with your reported RPM'S from an analog tach using a 27P Trophy.

I own a TR-21 as well with a 250 HP, that runs over 80, and have tested and used every Mercury prop made, while dialing in my setup....

I had a DDT hooked up and The analog tack @ 6000 was off 5rpm, DDT showed 6005 rpm. Something you might not have thought of is our altitude difference. All boats run fast down here.

[tomloans]

make sure you have full throttle at the motor when you step on it.

[topwater1956]

make sure you have full throttle at the motor when you step on it.

That's the first thing to check when you buy a boat new or used.

[tomloans]

IN other words, without the motor started, give it full throttle and see if the butterfly is fully open. if you grab the butterfly and you can open it even more when you have your hot foot pedal to the metal, then you are not getting full throttle. I bet that's whats going on here.

Nevermind it looks like you already did this. :)

[Savage]

I had a DDT hooked up and The analog tack @ 6000 was off 5rpm, DDT showed 6005 rpm. Something you might not have thought of is our altitude difference. All boats run fast down here.

I'm confused here IF the motor tops out at 5000 RPM, then how did you verify that the RPM's at "6000 was off 5 RPM"??

Seems impossible to do without the motor actually turning 6000 RPM, but you say it can only turn 5000 RPM.....

[EuropeanAM]

I'm confused here IF the motor tops out at 5000 RPM, then how did you verify that the RPM's at "6000 was off 5 RPM"??

Seems impossible to do without the motor actually turning 6000 RPM, but you say it can only turn 5000 RPM.....

I thought the same thing- then I remembered where the RPM limit was on his engine, so.....

[leonreno]

I took it as on his old boat he had the ddt was hooked up that is how he knows that prop will run that boat to the speed he stated, on his original boat with the same setup.

[topwater1956]

I'm confused here IF the motor tops out at 5000 RPM, then how did you verify that the RPM's at "6000 was off 5 RPM"??

Seems impossible to do without the motor actually turning 6000 RPM, but you say it can only turn 5000 RPM.....

I still have my other boat and took it back out with the DDT to check the analog tach and it showed 6000 rpm and DDT showed 6005 rpm. I have already
checked the boat i'm having problems with and @ 5000 the DDT showed 4999 rpm which is pretty accurate for a analog tach.

[topwater1956]

I took it as on his old boat he had the ddt was hooked up that is how he knows that prop will run that boat to the speed he stated, on his original boat with the same setup.

Your right.

[EuropeanAM]

Terry- I guess the "exact same boat and motor combination" is where the confusion is coming in. This engine, as configured from the plant (or any "exact same" engine) will not achieve 6000 RPM's as that is well in excess of the RPM limits.