HIgh RPM's
 

So I just got my boat back and took it out last night, and it seems like the RPM's are running high. They are running around 4 - 5000 at riding speed. Maybe I just never noticed they run that high but I am almost positive they have never run that high. What could this be from if it is an issue?

That's high.....

I notice higher RPM's when I run more weight in the boat (people or ballast). If it was not the case I would check the trans fluid level or propeller...

It's not the weight as when I ran it with no weight full throttle it hit almost 5500 .

"just got my boat back"


from what? new prop? 5500 rpm's with no weight aint right.

When you say "you just got it back", I asssume you mean the dealership. Is it the same prop you sent it in with? I have heard of props getting switched at the dealership for test runs on other boats and other more nefarious reasons.

I just got it back from having a new rudder seal and bushing put in.

x 2

There are several possibilities. First one is that the Tach is not reading correctly now. A bunch of possibilities of different parts slipping in the driveline. Last possibility is that the dealer slipped you a different prop which will be great wakesurfing.
Things slipping in the driveline will get worse quickly. If it's the Tach reading wrong you could probably hear that the engine was not sounding any different than normal when riding, until you looked at the tach.

Engine sounded normal while riding. What ticks me off is the dealer charges to "water test" it so how did they miss this? I will snap if they switched out my prop. Is that really something dealerships do? The dealership seem like very nice people and I can't imagine they would engage in such shadyness. This is a new dealership I have been working with though and every time I have gotten the boat back (3 times) the past 2 months there has been a new issue. I guess this is what I get for not taking it to the dealer I trust (90 mins away) vs the new dealership (30 mins away) I have been taking it to. It is just with a baby now it is so hard to find the time to take the boat all the way to Orlando but It looks like I am going to have to find the time cause this is getting out of hand unless it is common for MC's to suddenly start having all kinds of problems at 3 years old/400 hours.

Probably the prop is the same and the tach is just off. If the dealer took off the prop to work on rudder there is a slight possibility that it was accidentally switched.

Can I hurt the boat running it if it is just that the tach is off?

You can if you are wrong

Good point. Better safe than sorry I guess.

Is there any way to troubleshoot it to figure out what the issue could be for probably one of the most un-mechanically inclined people in the world?

They could have shorted out the tach, or accidentally bumped a wire and its now not making good contact. And I say this because you have to remove all the interior in the rear lockers to get down to the rudder assembly. I would call them up and tell them about your situation. If it was working fine before hand and is now not, any reputable shop should fix it for you.

anything over 5000 rpms and youre pretty close to redline on most 350 based engines.

You should definetly know if youre close to that by the sound - it would be screaming pretty good at that vs. ~3000-3500rpms which would likely be closer to normal rpm at riding speed (20s)

doubtful rpm guage is off - this is tied very closely to engine electronics. my guess would be somewhere in the driveline slipping - maybe they didnt put the spline back in the prop on reassembly -easy miss.

Since you just had rudder work done I would take a good guess it is related to your prop. The slightest bend (even if not noticeable to the eye) can cause RPM's to fluctuate. I would pull that prop and check it out thoroughly and check the shaft as well. If something is bent it will throw your RPM's off and it's slightly ironic that this just so happened after having transom/rudder work done.

Do you mean the key-way turning the prop?

If it were mine, I'd check the right prop first. If it is correct, my next step would pull the prop and double check there is a key way there. If those checked out then I'd double check you RPMs. Do you have access to a timing light with a digital readout? If you do put it on plug wire number 1 and check the actual RPMs while on the water. If that checks out, its your Tach. Tachs do go bad, and it could be as simple as a loose connection.

I'm sure you would of mentioned this but is there any vibration?

1200 rpm idle is about right, but 5000rpm is almost full throttle. Any chance the prop shaft is spun loose.

Idle should be between 600-700, if it is 1200 then the tack is wrong. I had one on my old Nautique that would change to 6 cylinder mode and register as you describe.

Need more info to help you more.

mine idles @ 660