Mercruiser 3.0LX Rebuild

[maxumized]

As part of restoring my previously abused 97 Maxum 1750, I pulled the 3.0LX a couple of weeks ago and took it to a builder I've used in the past with my cars. Turns out he has experience with Mercruiser which is nice.

Long story short, it's time for a rebuild.

He's found a "hot" cam which I thought was interesting. As valvetrain stuff like guides, locks, springs, etc... are being replaced any way, the cam kit would end up costing only about $100 more than if I kept the stock cam. I believe he said comp or crane was the manufacturer. Problem is, I see nowhere that they make cams for anything other than v8 marine applications.

We also discussed milling the head down to up the compression, with the understanding that I'll be locked into premium fuel from now on. Although, no one gets into boating to save money, now do they. So, an extra 0.20/gal really won't make much of a difference.

The rebuild is quoted right at $1450. This includes all new bearings, rings, valvetrain, etc. Only the block, pistons, and rods will be original, but they will be checked / machined.

Any comments?

 

[IVAZ]

Re: Mercruiser 3.0LX Rebuild

$1450 and you will be reusing the pistons and rods. That seems a bit on the high side. I dont know much about the hot cam and milled head but those sound like mods for a street engine.

 

[fat fanny]

Re: Mercruiser 3.0LX Rebuild

Max I also own a 3.0lx and have read numerous posts on people who are considering increasing hp and performance out of this engine but if memory serves me correctly the concensus was you won't get much if indeed thats the plan besides getting it seaworthy again. I do though believe the rebuid cost is a little high especially when the rods and pistons are reused and no honing of the cylinder walls or deck being planned. But anyway I hope turns out well and she runs great post back cost and results for I'm considering the same on my 96 in a year so.

 

[fuzzybob]

Re: Mercruiser 3.0LX Rebuild

Max, You might want to do a forum search on cams. If your "hot cam" has a lot of over lap it could pull water into your engine. Lots of good info on the subject in the forum. Good luck on your project.

 

[Bondo]

Re: Mercruiser 3.0LX Rebuild

Ayuh,... I donno about this Hot Cam,... You need some #s to explain the term...

And,... I wouldn't deck the head, or the block anymore than necessary to Flatten them,...
If it's even Needed.....

3.0ls already have known issues with run-on,...
And,...
Detonation will Destroy a motor before you can even Hear it sometimes....

If I was going to Throw Away some money,...
I'd Waste it on having the rotating assembley Balanced......

 

[Howard Sterndrive]

Re: Mercruiser 3.0LX Rebuild

I pulled the 3.0LX a couple of weeks ago and took it to a builder
...
Long story short, it's time for a rebuild.

funny how that works.
If you took it to an insurance salesman, it would probably need life insurance.

He's found a "hot" cam

or a hot wallet to tap into
there's only 1 cam for a 3.0 marine engine and it's already the right hotness

We also discussed milling the head down to up the compression, with the understanding that I'll be locked into premium fuel from now on.

Find a rebuilder that's way too busy to talk about that sort of nonsense.

The rebuild is quoted right at $1450. This includes all new bearings, rings, valvetrain, etc. Only the block, pistons, and rods will be original, but they will be checked / machined.

sounds like the crank is damaged?

$1450 not bad with a reman crank.

Any comments?

just : diagnose before pulling an engine.

How was oil pressure?
What was the compression on all four?
What failed and why did it fail?

 

[Don S]

Re: Mercruiser 3.0LX Rebuild

I pulled the 3.0LX a couple of weeks ago and took it to a builder I've used in the past with my cars.

Wait till you find out that auto mechanics seldom realize that there is actually a difference in how marine and automotive engines work.

Personally, I say go for it, then let us know how many minutes of actual runtime you get out on the water.

 

[rodbolt]

Re: Mercruiser 3.0LX Rebuild

I agree with DonS.
and reuse a piston in a rebuild?
trust me bud your getting a patchem up by rusty bolt bob and a can of krylon not a rebuild.
ya coulda done a valve job without removing the motor.

 

[90sunbird]

Re: Mercruiser 3.0LX Rebuild

i just went trough what you are doing i have all the info you need it was a nightmare to locate all the stuff i shaved the head .40 uped the compression .75 of a point found a cam shop in washington state called delta cams who gound me a cam for 90 bucks then i installed 1.94 valves an 1.6 ex then i put a rodes lifter in to lessen the idle so i got no water sucked in. wich the cam guy assures me this would not be a prolbem i ported an polished the head and installed a msd ignition the cam gear should be replaced to a aluminum cuse it pressed on if you need help you can email me at

EDIT Don S Removed email address. Use the PM function no email addresses on the forums.

it does run very good now i think it was a 35 to 40 hp gain the engine is pretty much set up like 1/2 of a 5.7 the lifter boars are the same size and the head an chamber is the same size good luck

 

[Don S]

Re: Mercruiser 3.0LX Rebuild

wich the cam guy assures me this would not be a prolbem

Sunbird, Sounds like you just have the word of someone at this point, Have you actually run this on the water?

If so, did you record any varifiable numbers before the upgrade then after the upgrades?

 

[JustJason]

Re: Mercruiser 3.0LX Rebuild

Do some research and see if the volvo 3.0L 150hp uses a different spec'd cam.

 

[90sunbird]

Re: Mercruiser 3.0LX Rebuild

don s i did rebuild a merc 3.0 not a volvo, if you are asking if i dyno the engine no i did not but i have ran the boat for a season now and noticed an mph incresement from 40.5 to 44 mph i saw on gps, and i used the boat for wakebording and noticed much better pull out of the water i figure the horsepower has incrasement was about 35 to 40, so i have ran the boat at hi rpm for a time now i wont turn the engine over 4500 but the cam was set up to run in a wide powerband for marine engines with very little valve overlap it has a bit more lift and duration, that hurts low end and the larger valve 1.94s on the intake runs better at hi rpm but i installed bleed down lifters after my 2nd test run { i have ran them in cars before and saw improvements!!} it made a world of a diffrencefor lower end power i even increased my prop pitch form a 19 to a 21 with little or no loss of low end after the upgrades, and as far as compression i did take .40 of the head and raised compression to 9.3 to 10.0 so i am able to run pump gas 92 octane i did check the loss of cc on the head to mesure compression i dont recall the number. ive uped the acc. pump on the holy 2brl and keped the same jets, next i plan to install a spaceplate for the base of the carb then i ported an polished the head because th intake and exaust on the same side kills the flow opened valve bowls up a bit and wedge cut the flow stealing head bolt holes. i installed a set of timing gears and got rid of that dumb plastic cam gear. it was a bit of a chalange to do this because you cant open up your summit performance book to just buy upgrades you actually have to build a engine with your brain and take mesurements for piston valve clearence deck hight cyl cc. ect but i assure you it was done and tested by me a tech of 13 years in the automotive biusness there is no hearsay involved in this upgrade

 

[maxumized]

Re: Mercruiser 3.0LX Rebuild

As to whether the engine needed a rebuild? The compression readings were all below 100. And oil in the chamber helped the compression... rings. I think it needs it.

At the very least, I'll be dropping the cam idea.

I called to get the part number on the cam and the builder wouldn't provide it as it was a "custom grind" from Comp and they aren't allowed to release it to anyone but dealers? So the story goes. Next I asked for specs... I was provided with the following. 204i/204e duration, .454 lift, and 112lsa. This is where I got concerned. Is it reasonable to believe a cam with .454 lift was intended for use in a engine that had .252 lift as at stock?? Seems a bit extreme.

This whole deal has got me frustrated. No one likes to get taken for a ride, and that's exactly what I'm starting to feel like. I tend to do things myself most of the time, and this is exactly why. But, since I don't own a machine shop, my options are pretty limited.

 

[maxumized]

Re: Mercruiser 3.0LX Rebuild

Also - what about remans or new GM replacement engines such as the following:



http://www.perfprotech.com/store/pr...rrent-130-140-hp-NO-CORE-GM181BASE,24318.aspx

http://www.go2marine.com/product.do?no=196553F

http://www.perfprotech.com/store/product/Engine-GM-30L-L4-Stand-Rot-Non-Tin-GM181LC,75304.aspx

 

[Howard Sterndrive]

Re: Mercruiser 3.0LX Rebuild

I've never thought the 3.0 was a rebuild candidate.
If you can get a new one for $1900 why take any chances.

I can usually find a good used 3L runner with next to no hours on it. For the 25 hours/year most boats get used up north here, one can buy a 20 year old motor and it still young.
usually compression and oil pressure test fine.

One I picked up had 90 psi on one hole, but it was a valve - easy fix on a $100 motor.

Crack repairs on the block are what you want to be careful of...

 

[maxumized]

Re: Mercruiser 3.0LX Rebuild

This thread can be closed. Officially threw the rebuild option out when I purchased a new GM 3.0 today. I'm sure I'll be posting other questions later.

Thanks for all the opinions. I feel much better with this decision.