250pro xs loss of top end and rpm’s

[Savage]

Need to know the WOT RPM reading with each prop tested.

[Generator]

25 fury 5600 wot if you raise the jp boat slows down

24 fury 5800 if you raise the jp speed doesn’t change but you can get motor to hit 6000.

[lpugh]

That would indicate about 12% prop slip I would think even with the poles you should be able to get it down to 9 tp 10 which would equate to about 70. Try to borrow a 24 or 25 tempest as they may give you a little more lift freeing it up.
How high it the rooster tail at wot and trimmed for max speed
Does the boat require full trim up to get the speed up or slightly less, might check the striker plates for wear causing reduced maximum trim

I would connect a pressure gauge to the low pressure port and watch for any drop on that gauge as you approach max rpm and speed

After getting that information, I would consider either a 23 or 24 Fury and having it reworked. A reworked Fury will run higher and is not any more weight sensitive than a tempest and will out perform the tempest in all regards on most bass boats,
Be sure the poles are not dragging in the water at all

[lpugh]

Sorry I ran two different props last weekend. One was a 25 fury three blade the other was a 24fury three blade.both are known good props with less than 20 hrs and no damage. Both hit 70 and stopped. That’s going down stream on the river. Running up river they would only hit 67 mph. Fishing the Ohio river I get fuel almost every morning before going fishing and not always from the same gas station. I’ve run 87 octane with merc quick kleen #1 and #2 each time it gets fuel.

Now last sat night I got to run the boat on the water with mercury air/fuel gauges. At idle I was 110psi on fuel and 100psi on air. Ran the boat with gauges and pressure never changed at any speed from idle to wide open throttle.

I am very troubled by these pressures, are you sure these are accurate readings, as they would cause a loss of performance. should be seeing 109 fuel and 95 air +or- 1, 14.1 psi spread, this is critically important

[Generator]

Thanks for the replies. I haven’t tried a tempest but I do have a friend with a good one. My rooster tail has always been very low if none at all you can play with the trim and the boat lifts as it always has. The 25 fury is the original prop that used to run the boat 74-76 mph at 5750rpm. Mark croxton re worked the prop to stock as possible earlier this summer. I didn’t check the low pressure port on the vst I’ll try to get them ASAP.

The gauges are pretty new and borrowed from a mercury tech. I have a vidio of the motor at idle so I would have the 5,10 and 15 seconds after shut down. I can’t get the video to post so if I can email it to someone to post I’d be more than happy. Also I laid on the back deck to see if any water was spraying poles dragging or ladder wasn’t hitting the water. All looked ok.

[Macsimus]

I have a vidio of the motor at idle so I would have the 5,10 and 15 seconds after shut down. I can’t get the video to post so if I can email it to someone to post I’d be more than happy.

Upload the video to YouTube and then you can post the link here.

[Generator]

https://share.icloud.com/photos/0fqN...F4fpiCwnzxGNCw

[Generator]

I think this worked. Both gauges are on air and high pressure side of fuel.

[lpugh]

Reverse the hook up on the gauges and see if you have the exact same readings, If those gauges are accurate, you do have a problem. Also be sure there is no leakage at hook up points. Presure is low and leaks down to fast

[Generator]

https://share.icloud.com/photos/0Beh...QBQ_U2XFhyPJEw
this is the second trip. Did find the gauge for air was bad. The small gauge is fuel the big gauge is air. They stayed 13 psi different the whole time.

[Generator]

https://share.icloud.com/photos/0ec2...E9vzYXfWnbrSAw
this is checking low fuel pressure side. Big gauge is still on air small gauge is on the low side (vst)

[lpugh]

https://share.icloud.com/photos/0Beh...QBQ_U2XFhyPJEw
this is the second trip. Did find the gauge for air was bad. The small gauge is fuel the big gauge is air. They stayed 13 psi different the whole time.

To much difference,

should not exceed .3 psi variation from 14.1

You need to get these readings at WOT to be meaningful
The 22 psi at idle bothers me just little, again we need know to what it is at WOT. As 22 is getting very close to the minumum

In the video I a can not see the reading well enough to make any conclusions
I have installed high end 4in gauges, so I can see .5 psi easily, when anything is in question I check the gauges against a very acurate digital gauge on regulated pressure of 100 psi

[Generator]

To much difference,

should not exceed .3 psi

You need to get these readings at WOT to be meaningful
The 22 psi at idle bothers me just little, again we need know to what it is at WOT. As 22 is getting very close to the minumum

In the video I a can not see the reading well enough to make any conclusions
I have installed high end 4in gauges, so I can see .5 psi easily, when anything is in question I check the gauges against a very acurate digital gauge on regulated pressure of 100 psi

Sorry but I’m kinda confused. In post #24 you said I should have a spread of 14psi +or- 1psi. That’s right where I’m at the low pressure side of 22psi is also where it’s reads at wot. The readings in the video is dead on the wot readings.

[lpugh]

Sorry but I’m kinda confused. In post #24 you said I should have a spread of 14psi +or- 1psi. That’s right where I’m at the low pressure side of 22psi is also where it’s reads at wot. The readings in the video is dead on the wot readings.

should be seeing 109 fuel and 95 air +or- 1. …………………….14.1 psi .3 variation max, this is critically important. another words 13.8 to 14.4,

and if off I would prefer it to be on the high side!

I can see how that could have confused, hope this clears that up
Since the low pressure is still above minimum and does not fall off I think that rules out any starvation issues from that point back to the tank

If get what I was saying about reversing the gauges because they may not read exactly the same, you did state 13 psi difference, after switching the gauges around it show a 15 psi spread, that would mean you really have 14 psi difference most likely indicating a gauge issue

Hoping this is of some help Good Luck

[EuropeanAM]

95/109, +/1 1 psi. Variation is normally 14.7 @ 1000 RPM's.

Can't clearly distinguish readings on those gauges- definitely glad to see the pressures holding (that first video had the air dropping FAST).

22 psi on the low pressure side is not causing a problem.

[lpugh]

95/109, +/1 1 psi. Variation is normally 14.7 @ 1000 RPM's.

Can't clearly distinguish readings on those gauges- definitely glad to see the pressures holding (that first video had the air dropping FAST).

22 psi on the low pressure side is not causing a problem.

My service Manuel states 14.1 though it is a little newer than this motor, different specs or is there a revision?

[EuropeanAM]

That's from regulator calibration instructions (not in manuals).

[Generator]

Ok guys update. I took the boat 8hrs south to Don Weed and let him fix the boat. Turns out the belt tension pulley spring was bad/weak and letting the belt slip and chirp so that was replaced. My speed/rpm loss was due to the new compressor that was installed this spring. Don said the reed plate had lame/weak reeds only letting the compressor build up so much pressure it was essentially governing its self. So he replaced it under warranty due to being less than a year old. Took the boat out this past Friday and it’s back to full rpms and top speeds are back. Many thanks to Don for getting me fixed up.

[EuropeanAM]

Glad we could get you fixed up, Brian. Between the weak spring and weak reeds in the compressor, it simply couldn't produce enough air volume to allow the engine to "hit the high notes".