Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha One

[Scott Danforth]

Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

Yes, its 60 year old technology

 

[Bondo]

Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

The 3.0 liter is a stroked 2.5 that was available in the 1962 Chevrolet compact cars such as the Chevy ii

Ayuh,.... Not to be confused with the 2.5l GM corporate motor, the Iron Duke, a Pontiac design, used in cars, 'n trucks,.....

 

[slag]

Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

So I can buy parts for the 2.5 liter engine for a chevy II at an auto parts store (non electrical) and they will fit the 3.0 liter engine or are there enough differences that you have to buy mercruiser or aftermarket?

 

[oldjeep]

Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

So I can buy parts for the 2.5 liter engine for a chevy II at an auto parts store (non electrical) and they will fit the 3.0 liter engine or are there enough differences that you have to buy mercruiser or aftermarket?

Easier and cheaper to just buy the marine parts (did I just say that?) Because they have been using the 3.0L forever, the parts are common and cheap.

 

[thecca]

Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

I timed it yesterday in base mode... It was at 6 degrees BTDC (supposed to be at 2 ATDC). Put some 91 octane fuel and ran it a while.

My issue dissapeared, we went wakeboarding and we didn't heard a single noise, even under hard load/acceleration.

I guess gas and timing caused the issue... Thanks again for the help and I'll let you know if it comes back. I'm sooo happy.

 

[Scott Danforth]

Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

Ayuh,.... Not to be confused with the 2.5l GM corporate motor, the Iron Duke, a Pontiac design, used in cars, 'n trucks,.....

correct, 153 vs 151 cubes.

So I can buy parts for the 2.5 liter engine for a chevy II at an auto parts store (non electrical) and they will fit the 3.0 liter engine or are there enough differences that you have to buy mercruiser or aftermarket?

you could, however your limited to gaskets, valve train, engine tin, and hardware. the pistons, connecting rods, block, crank, etc are all GM specific for the 3.0 liter which is made in Mexico. you do not have to buy Mercruiser parts if you want core engine parts. that is GM industrial engine division. Available thru GM. however you need to go to a dealer that deals with industrial engines.

 

[Scott Danforth]

Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

I timed it yesterday in base mode... It was at 6 degrees BTDC (supposed to be at 2 ATDC). Put some 91 octane fuel and ran it a while.

My issue dissapeared, we went wakeboarding and we didn't heard a single noise, even under hard load/acceleration.

I guess gas and timing caused the issue... Thanks again for the help and I'll let you know if it comes back. I'm sooo happy.

Didnt I say put good fuel in it like on post 17 back on page 1

 

[thecca]

Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

Didnt I say put good fuel in it like on post 17 back on page 1

Yep but I don't know if timing or gas were the problem (probably both) since it took a while for the new gas to get in the motor (it blended with the 87 octane one for a few rides I guess...)

8 degrees off is way too much, the spark plug ignited the fuel way too early, the piston wasn't even at TDC when it did. No wonder why it made this sound.

As long as my engine works fine now, I don't mind which one was the problem...lol

Thanks

 

[81 Checkmate]

Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

Good news..........Keep us posted!

Now you know much more about your motor and how it works! Preventive maintance will be so...much better.

Good Luck!

 

[sti1471]

Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

That is great that you got your problem fixed. It is always good to hear a positive outcome, especially for issues that sound like it is a season ending issue.

After following this post from the start, I see you joined the forum here just this month. So welcome aboard.

I felt a little welcome hazing is in order to officially welcome you.
Hazing Theme: Always check the easiest solution, and listen to the advise given, it can save you some grays hairs and boring dry weekends.

Hi... I went on the water yesterday and noticed a strange sound coming from engine

Run the highest octane gas. You could be hearing pre-detonation rattle from low grade of gas.

Could be pinging from fuel. Try an octane booster or changing to a premium fuel. Confirm Timing. My 3.0 L with poor fuel sounds like it has marbles in it.

I switched from 91 to 87 octane gas 1 week ago (manual says it's tuned for 87 (regular) so I did put some in it...)

I think that maybe my timing gets off when engine is hot and under load...?

I think you may have answered your own question:

"I switched from 91 to 87 octane gas 1 week ago"

Strange coincidence the problem surfaced shortly thereafter???

I doubt this would make this kind of noise. I mean, knock or ping is not THAT loud.

Gas is good, I fuel at the same place since a couple of years and got the same fuel in my car, everything is fine.

Sound is really coming from the flywheel area. Timing maybe?
[/B]

my first thought is fuel since it is only under acceleration and only since you went from 91 to 87

I don't think a detonation / pre-ignition could do that kind of noise, not that loud.

Did a ride with the mechanic. He said that it's probably my timing that was off and fried the motor after a while...They're gonna check with the light to see where it is currently and call me back.

Did this call never come?

like Bondo said, going lean and detonation going on. Check the timing. You have to eliminate the possibility’s one by one….. instead of just guessing.

I am thinking that readjusting it back to factory will fix the problem. I think that the timing is off maybe 10 degrees.

I'm thinking it's a timing problem. He’ll time it.

Make sure you lose this guy’s number.

I timed it yesterday in base mode... It was at 6 degrees BTDC (supposed to be at 2 ATDC). Put some 91 octane fuel and ran it a while.

My issue disappeared.

I have seen way more times on this board than you can count where boaters were sure it was not this or that. After 3 pages of posts, it turned out to be something mentioned back on the first page.

Start with the fuel, you stated before you changed from 91 to 87 and now the problem is here, I don't think that is a coincidence.

And finally, my personal favorite.

Didn't I say put good fuel in it like on post 17 back on page 1

 

[cbrcolt45]

Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

ok so my boat is doing the same exact thing... everything is the same even the engine... I run 87 octane... (didnt know any better).. so if i drain my gas and fill with 97, think it will go away? or would i have to adjust timing? only asking because i have no idea how to adjust it....

 

[thecca]

Re: Strange noise coming from motor under acceleration... Mercruiser 3.0 with Alpha O

Hi there! Try easy things first. I know this is not easy to deal with, but yes try to use 91 instead AND check timing.

To adjust it, you need a timing light and a jumper wire (for the special timing procedure).

The procedures are available on this forum and almost everywhere else on the internet . If you have the same motor than me, your timing (in base mode) needs to be -2o BTDC.

Good luck and don't hesitate if you have other questions, people here are really helpful!

 

[1985 Century Mustang]

I'm experiencing a weird sound as well. But before I go crazy with everything, I'm considering to do higher octane and timing check. Maybe I can do an octane boost since I have 3/4 of a tank of 87.
Question: Was this the same or similar sound you had?

 

[Bondo]

I'm experiencing a weird sound as well. But before I go crazy with everything, I'm considering to do higher octane and timing check. Maybe I can do an octane boost since I have 3/4 of a tank of 87.
Question: Was this the same or similar sound you had?

If you don't stop posting in these antique threads, I'm going to ban you from iboats,.....
You don't have detonation, you have a bearing knock,....
Pull the motor, tear it down, 'n see if it's rebuildable,.....

Please read, 'n follow our posting rules, 'n guidelines,....
There's a link in my signature,.....