Top End RPMs

[sten76]

I have a 2002 ProStar 209 Sammy with the LTR engine. Just took it in for the Spring Tune/Clean. Before the service, last weekend, I was running around 4900 RPM top end with a speed around 50 MPH. Now after the service I am running around 4700 RPM with the top end speed still at 50 MPH.

Does this make sense? Why would my RPMs go down and speed stay the same?

Thanks for any input.

Not to me, 200 RPM's isn't much, but I would call the service manager and see what he says.

[DanC]

What are you using to check your speed with?
If it is the speedos, the calibration could have changed on them. They also are inaccurate above 39 mph.
If it is with the Perfect Pass or GPS, I got nothing.
Leroy has the best idea, call the manager and find out what new fangled gas saving device he installed.

[sfitzgerald351]

I'm not at all familiar with the LT-1, but every 350/351 motor I've driven, in boats or cars, usually topped out at 4500-4600 rpms... 4900 seems high to me. Maybe the tach isn't all that accurate as well?

Let us know what you find out.

[Stritt]

My LQ9 shows about 4950 WOT. I think my MCX was in that range as well. I don't think he really has a LT1, I think he meant to say LTR.

[Footin]

Old gas in the tank?

My LTR1 is around 5000 RPM and 44.x MPH at WOT.

[BarefootWt]

This does not make sense off hand. Are you reading an analog gage or digital gage? Maybe the calibration changed? Maybe they swapped props by mistake? Maybe the speedometer is partially clogged giving false indications (don't know how dirty the water was where the marina may have test drove your boat). Maybe they changed the timing and it is a combination of things like timing and gage calibration? Just some off-hand thoughts...but I would call and ask your repair center.

[sten76]

I called the dealer and they were going to ask the techs. The boat had not been run for about a year before I put in the water last weekend. So maybe after they changed the oil, fixed a skeg, the front skeg was bent, it may be running the same speed but lower RPMs. The prop has not been changed, although I will be putting an Acme prop on soon. It runs great, with no vibrations, but just at a lower RPM.

Any ideas? Oh yeah, I just put in a full tank of 93 octane gas.

[sten76]

The tech stated that RPMs can changed as much as 200 depending on many variables. From how much gas, to the type, to the weight of those in the boat. They said it was fine.

Thank God.