4.3 Engine Noise in neutral?

[PayForYourGas]

Hi all,

I just purchased a 2003 Crownline 180BR with the 4.3 Mercruiser, and have noticed an engine noise recently that I can only really hear in neutral . I first started hearing it at the dock when I'd put the boat in neutral and fast idle it at around 1000RPM. Its not as deep as a knock (from the knocks I've heard at least), and not as ticky as a valvetrain noise, it seems like it somewhere in the middle. It goes up and down with RPM's from what I can tell, though I don't like to rev it too much in neutral. .

Once I put the boat in gear I don't hear it (I'd have to have someone else drive and stick my head in there to confirm 100%). I have good oil pressure at 40+ PSI, and the boat starts and runs like a top. From what I can remember, I had the outdrive trimmed up as well.

I know its hard to diagnose over the internet, but is this an engine noise or is it possibly a cv joint or u joint making noise in neutral with the trim up? Thanks in advance.

 

[Bt Doctur]

under full trim the angle is not severe enough to damage the U joints. Now if you mean full trailer height , that not recommended

 

[AShipShow]

A couple things come to mind... one being your shift cable adjustment... The only thing not spinning through the entire drive in neutral is the prop shaft... If your shift cable is out of adjustment, the dogs might be slightly engaged and making a knocking noise... Also, as you suggested, could be a bad ujoint on the yoke... Try steering the drive left and right and up and down and see if the noise changes...

Also, when you say trimmed up, I assume you mean trimmed to the max up position with the trim button and not using the trailer button. Thats brutal on your ujoints running trimmed the whole way up like its being trailered.

 

[alldodge]

Howdy

Could be either the coupler has some wear on it, loose U joints or gimbal bearing.

When was the last time the engine alignment was checked?
Also when were the U joints checked and greased?

 

[PayForYourGas]

The trim was trimmed basically all the way up, not in trailer mode

I just purchased the boat so I have no clue when alignment or anything else was checked.

So I take it this is sounding more like a driveline issue?

 

[AShipShow]

If it only makes the noise in neutral and not in gear then that just about definitely isolates it to something in the drive.

Still sounds like a shift cable to me, but could be any of the above things...

Follow this video from a fellow iboater to check your shift cable.

https://www.youtube.com/watch?v=-s_tgevX2aI

 

[alldodge]

The trim was trimmed basically all the way up, not in trailer mode

With the drive being up (not trailer) its probably the U joints knocking. If the trim up is not adjusted correctly then it may be going up to high and the U joints are in a slight bind. If it quiets down with the drive full down then that would be the best guess right now

 

[PayForYourGas]

I'm going to have to give it a try in the water again and see if it quiets down with the trim full down; not sure if I'll be able to hear it with muffs on and the exhaust out of water.

 

[Rick Stephens]

If you have little experience with stern drive boats you might not know this, but never start a motor with the drive trimmed up higher than operating range. Raised higher than that and the CV joint is binding and the drive shaft is under pressure. This will tear things up and usually sounds pretty bad.

 

[R055]

And just making sure but you're not riding the boat with drive fully up correct?

 

[Rick Stephens]

And just making sure but you're not riding the boat with drive fully up correct?

Never even run the motor with the drive not down in operating range.

 

[andrewterri]

To expand on what was said earlier, when your in the water idling in gear turn the steering wheel from lock to lock. As you approach max left or right turn you will hear a clicking if your alignment is off or your u joints are bad. This is what I did with my boat and found out my alignment is bad.

 

[PayForYourGas]

I've never heard any sort of clicking before when turning max left or right while in gear