Speed and RPM don't seem to match up - do I have an engine problem or....

[dmanmtl]

Ok, I originally was sure I just had a tachometer issue but now I am worried something else might be wrong.

The boat: 2003 Bayliner 175BR, 3.0 mercruiser inboard

The boat seems to run great - it had a full tune up before I bought it, start immediately from cold or hot, pulls out of the hole really fast (seems fast - I don't have a lot to compare to).

The issue I have is at full throttle with only me in the boat it does about 45-47 MPH (GPS verified), which seems acceptable, but the tach never goes above 3000 RPM. I checked the settings on the back of the tach it seems to be set correctly.

So, I either have a defective tach or my engine is not able to get up to full Max RPM. It seems to me however that if it was really an engine RPM problem the boat would not run as fast as it does.

Any advice would be appreciated. I have already received so much invaluable input from this great community, so thanks in advance!!

D

 

[Silverbullet555]

Re: Speed and RPM don't seem to match up - do I have an engine problem or....

You're not doing 45 at 3000RPM with that boat and motor. On the tach, you checked the settings. Go back and turn all the screws stop to stop a couple times then reset. This will usually rub off any corrosion and get them back to working again. If it doesn't fix the issue, then go to next steps.

 

[dmanmtl]

Re: Speed and RPM don't seem to match up - do I have an engine problem or....

When you say reset - what does that mean? is there a reset process? apologies a bit confused by that....

 

[dozerII]

Re: Speed and RPM don't seem to match up - do I have an engine problem or....

Turn the setting pot on the back of the tach slowly to each setting, then back to the correct one, He's saying it may clean the contacts and make the tach work properly.

 

[tdshepard]

Re: Speed and RPM don't seem to match up - do I have an engine problem or....

My tach did not work correctly on my 3.0 four cylinder until I set the tach at 8 cyl! Be sure to "push in" as you rotate the tach settings....you should be around 4600 rpm at that speed.

 

[QC]

Re: Speed and RPM don't seem to match up - do I have an engine problem or....

If that's an engine problem I want some uh 'dat