4.3L Alpha 1 Noise in Idle from Reverse?
 

Hello Fellow Mariah Owner's Club Members,

I am a newer owner of a 1995 Mariah Barchetta with a 4.3L Alpha 1. My wife and I have been loving our time this summer on the water (10 full days and 5 half days), but just as we were loading up from our last trip we started hearing this odd noise:

If the boat is driven in reverse for a minute or so, as soon as it is shifted back to neutral a noise similar to trying to start a car after it is already running is heard (sort of grinding if I had to pick one word). Then, if it is shifted to forward, the noise goes away.

This only happens in the transition from reverse to neutral (and the noise is only heard in neutral), and only if it has been previously in reverse for a while.

If you have any further questions, please let me know.

I greatly appreciate your help.

Thank you and have a great day,

Kris

Re: 4.3L Alpha 1 Noise in Idle from Reverse?
 

Re: 4.3L Alpha 1 Noise in Idle from Reverse?
 

Hi WW,

Thank you very much for your response. I will take her to our mechanic and let you know what he finds. Are there any other high probability causes that I could suggest if that is not the issue?

Thanks again and have a great day,

Kris

Re: 4.3L Alpha 1 Noise in Idle from Reverse?
 

I had the same thing happen on my last trip. Same noise and all, just with a 7.4L and a Bravo I! Towed it home (4hrs), dropped it off at the local Mercruiser service facility, mechanic states he couldn't find anything wrong with it. I insisted they test it further, he showed me the log that shows they shifted in and out of gear over 200 times in and out of the water, at various shifting speeds and couldn't replicate it.... He seemed to think perhaps the drive home might have "knocked something back into place"... So I've got an open appointment with them again just in case it happens again.

Re: 4.3L Alpha 1 Noise in Idle from Reverse?
 

Hi Chris,

I either hope to have the same situation as you, or I hope my mechanic finds the issue and it is relatively inexpensive to fix. I will let you know regardless of the outcome.

Thank you and have a great day,

Kris

Re: 4.3L Alpha 1 Noise in Idle from Reverse?
 

So, my mechanic dug into this issue and he came up with the same thing as your mechanic Chris...nothing.

He even had me stop in while it was running and it would not replicated the noise. At that time we did notice some slight vibration and we agreed to pull the outdrive.

I know you all are thinking it has to be the gimbal bearing or U-joint, but he checked those and said they were in good working order. The slight vibration even existed after he pulled the drive off.

He then checked the engine mounts and everything else and found that the power plant is an earlier 4.3L vortec that was labeled wrong. These earlier versions do not have a certain part (I'm blanking on the name) designed to reduce this slight vibration.

So, all in all, he charged me 50 bucks for this in depth inspection, which for the peace of mind is well worth it in this case. However, we still do not know why it makes the occasional grinding noise when going from reverse to neutral.

If any one else has any insight on this issue, please let me know.

Thank you for all your help and have a great day,

Kris

Re: 4.3L Alpha 1 Noise in Idle from Reverse?
 

'tis called a 'balance shaft'. Here's a little more info on the 4.3 history.

Identification Tips for MerCruiser 4.3L Longblocks

1986 - 1992, 14149R5
Non-balance shaft, mechanical fuel pump, roller camshaft, one piece rear seal.
A. Easily identified by metal 10 bolt short front cover similar to 5.7L.
B. Some nQn-balance shaft engines were produced without a manual fuel pump. This engine will fit either application with a fuel pump cover if manual fuel pump is not needed. C. All 12 intake manifold bolts are at 90 degree angle to cylinder head machined surface.

1993-1995 806347R5
Balance shaft, no mechanical fuel pump, roller camshaft one piece rear seal.
A. Easily identified by tall metal 10 bolt front cover different from 5.7L.
B. All 12 intake manifold bolts are at 90 degree angle to cylinder head machined surface.

1996- 1998 807736R5
Balance shaft, no mechanical fuel pump, roller camshaft, one piece rear seal, "Vortech" cylinder heads with rocker ball & stud valve train.
Note:
A. Vortech heads are easily identified by only 2 bolts per corner of intake manifold for a total of 8.
B. The older crankshafts rear flange are 0.123" longer and have a small pilot bushing hole in back.
C. Plastic 6 bolt front cover.

1999- 2002 864256A1
Balance shaft, no mechanical fuel pump, roller camshaft, one piece rear seal, "Vortech" cylinder heads with roller rocker arm valve train.
A. Vortech heads are easily identified by only 2 bolts per corner of intake manifold for a total of 8.
B. The cylinder head actually went to the "roller rocker arm" in 2000. Mercury Remanufacturing has elected to change coverage to coincide with the 1998/1999 crankshaft change as the customer would have to change flywheels to coincide with the crankshaft used. The 1999 customers will actually get a product improvement with the roller rocker arms and will not have to make any changes to their current parts.
C. The crankshaft has a 0.123" shorter rear flange and larger pilot bushing than previous versions.
D. Plastic 6 bolt front cover.

Re: 4.3L Alpha 1 Noise in Idle from Reverse?
 

Hi Mikey,

Great information, thank you.

The one thing that I am slightly confused by is that my Barchetta is a 1995 model, so I find it interesting that the engine in it was last manufactured in 1992.

I would be interested in the differences between mechanical and manual fuel pumps.

Thanks again and have a great day,

Kris

Re: 4.3L Alpha 1 Noise in Idle from Reverse?
 

Updating this thread after a very long time because we finally found the answer to our issue.

I do not believe I mentioned this before but, this symptom never occurred while I was driving.

It appears that our ignition switch is slightly broken, such that after the key is turned to the start position, it will not completely go back to the on/run position without an extra counter-clockwise twist (almost as if there is an extra notch that it gets stuck in).

This extra twist is something I have always done with any vehicle to make sure it is in fact in in the on/run position. However, my wife apparently did not do this extra twist and it appears in the right circumstance the boat will try to engage the starter while running.

So, for any of you that may have a similar symptom, check your ignition switch and hopefully that is your answer as well.

Have a great day,

Kris

Re: 4.3L Alpha 1 Noise in Idle from Reverse?
 

Hey Mikeyt, Do you have similar info on a 7.4L 454?