Mercruiser 3.0 1988

[alpha-newbe]

Is there a good reference manual or source that specifies the many specs for the 3.0 4 cyl.
I am in the midst of getting initially a non running engine running and things are going pretty well so far. I am looking for the correct idle speed for this engine currently. Also can someone verify that the shifter interrupt switch will not move back and forth if the boat is out of the water and running on muffs.

Thank you for your help.

 

[Scott06]

Is there a good reference manual or source that specifies the many specs for the 3.0 4 cyl.
I am in the midst of getting initially a non running engine running and things are going pretty well so far. I am looking for the correct idle speed for this engine currently. Also can someone verify that the shifter interrupt switch will not move back and forth if the boat is out of the water and running on muffs.

Thank you for your help.

yes shift interrupt should not trip while out of the water and no load is on the prop. If it does usually indicative of worn shift cable or corroded linkage in bellhousing.

625-650 is a decent SWAG idle speed.

Best place for info is the factory Mercruiser service manual which exact manual depends on your serial number. If you plan on working on it yourself get the engine manual and the drive manual

 

[alpha-newbe]

Thank you for your prompt reply,

I did go to mercury website and entered my serial number, no luck on the manual for some reason.

I am in the midst of a rattle sound that does not change with the RPM's. It is intermittent and generally starts at 2500 rpm. Then will stay clattering randomly as I decrease rpm. Then all of a sudden it will stop and I can rev the engine and it runs super smooth. But ultimately the engine runs extremely will other than this clattering sound. The engine does not appear to be bothered by the sound as it stays running smooth other than my concern for the noise.
View attachment IMG_8922.MOV

 

[Scott06]

Thank you for your prompt reply,

I did go to mercury website and entered my serial number, no luck on the manual for some reason.

I am in the midst of a rattle sound that does not change with the RPM's. It is intermittent and generally starts at 2500 rpm. Then will stay clattering randomly as I decrease rpm. Then all of a sudden it will stop and I can rev the engine and it runs super smooth. But ultimately the engine runs extremely will other than this clattering sound. The engine does not appear to be bothered by the sound as it stays running smooth other than my concern for the noise.
View attachment 408340

yes needs to idle a bit lower. Not sure if something is loose inside the flywheel cover or flywheel is loose (or the metal cover on front side of flywheel cover) ?

I would be inclined to pull the drive and run it ( connect water by jamming hose in bellhousing or connect to hose up from outdrive).

this would separate any issues gimbal U-joints or drive. hard to tell from keyboard but would be thinking its in the flywheel area

is this a new to you boat?

 

[Scott Danforth]

since your motor is older than 15 years old, you may have to call your local merc dealer for the manual. the website only goes back a few years

 

[Bondo]

Ayuh,...... Welcome Aboard,...... Is the drive on it,..??
If so, is the drive down,..??
Idle should be 650/ 700 rpms,....

If the drive is on the boat, 'n tilted up, my guess is yer shredding the u-joints,....

 

[alpha-newbe]

yes needs to idle a bit lower. Not sure if something is loose inside the flywheel cover or flywheel is loose (or the metal cover on front side of flywheel cover) ?

I would be inclined to pull the drive and run it ( connect water by jamming hose in bellhousing or connect to hose up from outdrive).

this would separate any issues gimbal U-joints or drive. hard to tell from keyboard but would be thinking its in the flywheel area

is this a new to you boat?

This is a new to me boat. The part that stumps me is that I have it running so smooth. Then all of a sudden the strange noises start happening then they disappear just as fast as they started. I did hear a video last night that sounded very similar and it was the timing chain someone had posted on youtube. I will continue to do some investigating. Mainly the approach is with minimal cost. I did buy the boat in non running condition. Being a 1988 Cimaron runabout 17ft it is all like new condition except for the normal wear and tear, and obviously the engine weirdness. I did get it running the day after I installed the battery. Determined it was not starting due to a bad solenoid or starter. Started with the 16.99 solenoid. Replaced it and the engine fired right up. So some things are going well at least.

 

[Scott06]

This is a new to me boat. The part that stumps me is that I have it running so smooth. Then all of a sudden the strange noises start happening then they disappear just as fast as they started. I did hear a video last night that sounded very similar and it was the timing chain someone had posted on youtube. I will continue to do some investigating. Mainly the approach is with minimal cost. I did buy the boat in non running condition. Being a 1988 Cimaron runabout 17ft it is all like new condition except for the normal wear and tear, and obviously the engine weirdness. I did get it running the day after I installed the battery. Determined it was not starting due to a bad solenoid or starter. Started with the 16.99 solenoid. Replaced it and the engine fired right up. So some things are going well at least.

Read bondo post above if outdrive is all the way up and you run above idle speed the ujoints will make noise.

before you spend too much time and money if you haven’t make sure your stringers and transom are solid.
would also pull the drive and inspect the bellows gimbal and ujoints, pressure test the drive

 

[alpha-newbe]

Ayuh,...... Welcome Aboard,...... Is the drive on it,..??
If so, is the drive down,..??
Idle should be 650/ 700 rpms,....

If the drive is on the boat, 'n tilted up, my guess is yer shredding the u-joints,....

Thank you for your input. I would never do that. I am not new to boating just this is a new boat to me. I do like your suggestion in taking off the lower unit and running then to see if it could be the problem.

 

[alpha-newbe]

Read bondo post above if outdrive is all the way up and you run above idle speed the ujoints will make noise.

before you spend too much time and money if you haven’t make sure your stringers and transom are solid.
would also pull the drive and inspect the bellows gimbal and ujoints, pressure test the drive

Thank you for your suggestion about removing the drive. The sound could be transferring into the engine possibly. I will be scoping through the spark plug holes tonight just to take a peak.
I can run above idle speed and the noise does not always occur.
This is a tricky sound do to its intermittent behavior.

I truly appreciate your help and insight.

 

[Scott06]

Thank you for your suggestion about removing the drive. The sound could be transferring into the enginep possibly. I will be scoping through the spark plug holes tonight just to take a peak.
I can run above idle speed and the noise does not always occur.
This is a tricky sound do to its intermittent behavior.

I truly appreciate your help and insight.

still not sure if the drive is up or not.... if up just trim the drive down and run it at that speed first see if the noise goes away.

re the comment about timing chain - the 3.0 uses a timing gear set

 

[alpha-newbe]

still not sure if the drive is up or not.... if up just trim the drive down and run it at that speed first see if the noise goes away.

re the comment about timing chain - the 3.0 uses a timing gear set

Drive is always down when running. Never up.

 

[alpha-newbe]

The shift cable is set correctly as well. Initially it was set at 5.5 with a pinned barrel nut. no adjustment could be made. So installed new stainless cable sleeve with adjustable barrel nut. Now the cable is set at 6.00" on the money. Forward gear locks in place and reverse locks in place. Before my improvement the shifter was not locking into gear correctly. I had thought that, that may have been the noise. Gears not meshing correctly. But now it is engaging perfectly.

 

[Scott06]

Drive is always down when running. Never up.

ok thanks. it seems to be coming from rear of engine.

I would think its either in gimbal bearing , ujoints or something in flywheel area is loose and rattling or flywheel and or coupler is loose. The latter will require pulling the engine or at least lifting it so you can get the flywheel cover off. to pull the engine you have to pull the drive hence pull the drive run it and see.

 

[alpha-newbe]

ok thanks. it seems to be coming from rear of engine.

I would think its either in gimbal bearing , ujoints or something in flywheel area is loose and rattling or flywheel and or coupler is loose. The latter will require pulling the engine or at least lifting it so you can get the flywheel cover off. to pull the engine you have to pull the drive hence pull the drive run it and see.

I will be doing a bit more checking with stethoscope and camera prior to any major removal of hardware. it sounds like it is coming from the left side of the engine. near the pushrod/lifter panel that can easily be removed. Do you know if the lifters are hydraulic lifters? I would think they are, but have heard about flat tappet style as a possibility.

 

[Scott06]

I will be doing a bit more checking with stethoscope and camera prior to any major removal of hardware. it sounds like it is coming from the left side of the engine. near the pushrod/lifter panel that can easily be removed. Do you know if the lifters are hydraulic lifters? I would think they are, but have heard about flat tappet style as a possibility.

yes they are hydraulic flat tappet. the lifters are accessed behind the two panels. You can pull the rocker cover and see if there is any play in the rockers arms. They can be mal adjusted or rocker stud can pull out or nut can loosen. noise doesn't sound like that to me.

I did see one time where a blown head gasket was letting a little water in and making almost a rattling noise under load. again hard to tell from a video noise wise

 

[Alumarine]

If your motor is a 1998 it should be covered in Mercruiser Service Manual Number 10, Publication Number 90-14693-1
Ebay has a number listed, some of which show which engine serial numbers they apply to.

Search for Mercruiser 90-14693-1

 

[alpha-newbe]

If your motor is a 1998 it should be covered in Mercruiser Service Manual Number 10, Publication Number 90-14693-1
Ebay has a number listed, some of which show which engine serial numbers they apply to.

Search for Mercruiser 90-14693-1

My motor is a 1988. I heard mention of the adult section on this website having manuals? Could not find it.

 

[nola mike]

My motor is a 1988. I heard mention of the adult section on this website having manuals? Could not find it.

They're gone unfortunately. For years brunswick didn't care until they realized that there was still money to be made by selling them.

 

[Scott Danforth]

manuals are copywrite protected

you can buy used on ebay.

Mercruiser Manual 10 for sale | eBay

Get the best deals for Mercruiser Manual 10 at eBay.com. We have a great online selection at the lowest prices with Fast & Free shipping on many items!

www.ebay.com

I believe its manual 10.