3.0LX Rebuild

[maxumized]

Background:

Bought a 1997 Maxum 1750 w/ 3.0LX this summer. Boat always cranked extremely slow, went through a few starters, had problem with hot starts, and never would reach operating RPM at wide open throttle. A compression test showed even psi across cylinders, however, all were around 100psi, low according to the manual specified 140psi. Also burned a little bit of oil. I'm guessing its already a reman engine as it has a Jasper Engines decal and serial #.

I've rebuilt a few automotive engines and consider myself fairly handy so I'm thinking of tackling a pull and rebuild on the motor. Will have the machine work done at a shop I've worked with over the years.

Questions:

If it's truly a reman, who knows what Jasper Engines bored over... if they went .030 over, how much more tolerance is there in the walls to allow for another bore? Do they make .060 kits, etc.

Anyone increase the compression on these engines?

Anything to stay away from with the head work?

I'm looking for a very strong running 4 cyl and will probably be rebuilding the carb myself. This engine has the delco est ignition... is this simialr to HEI and can it be or should it be upgraded with a coil?

I'm hoping for a strong, worry free season in 2009.

Any recommedation or advice is appreciated.

 

[chiefalen]

Re: 3.0LX Rebuild

Measure the bore, however i would be lookin at he head to see why the compression is low.

Do a leak down test, might not be the cylinders at all.

 

[Bondo]

Re: 3.0LX Rebuild

Ayuh,...

Some or all of your questions will be answered upon tear-down...

If overbored, the pistons will be stamped so,+ Yes, .060 kits Are available if needed...

As for the Head,... Raising the Compression is easiest by just cutting the head,.. Shave .010 or so off it...
Your Machinest will know how much...
Anymore than that,.. Porting, polishing, port-matching, oversized valves, etc,...
Hey, Whatever trips your trigger,... Just come on back,+ let Us know if it's Worth the effort,+ Expence....

And lastly,... That Igntion will service Whatever motor combination you put together,.. Just Fine....

 

[chiefalen]

Re: 3.0LX Rebuild

You do know you ain't turning that little 3.0 into a monster 300 hp motor.

Your gonna get the most 140 hp out of it.

Why though 2 rebuilds on a 97' im thinking ?

Could someone:
1- Ran it at wot all the time everytime.
2- Never took care of it, with oil changes and such.
3- Or a combination of 1 and 2.

Keep us posted.

Good luck !

 

[maxumized]

Re: 3.0LX Rebuild

thanks for the tips.

I'm going to try and determine if the valves/heads are leaky or if its the cylinders before deciding to do a rebuild or maybe just a head rebuild.

Chiefalen, I only know of two owners before me.

The guy I bought it from owned it for less than a year and had it in the shop frequently. They did all sorts of work to new starters, new prop, outdrive bearings/bellows, etc... but never on the motor itself. Apparently the shop never thought it was a problem that the boat would never turn anything above 3000 rpms. Needless to say, I do my own work now.

The guy that owned it before him I have no idea how he treated it other than it sat out for a long time.

Does anyone know if jasper engines was a supplier to Maxum for new builds in 1997? If not, I'm assuming it was a reman replacement motor.

And don't burst my bubble about the power of the 4 cylinder ... I know its not gonna be a monster, but squeezing the most I can out of a good running 4 cyl will suit me just fine. It's just a 17' boat, so it should be fine for me. Hell, if it will reach opearting RPM at WOT, it will be a massive improvement over current conditions.

 

[DJ]

Re: 3.0LX Rebuild

Sick engine aside, make sure someone wasn't monkeying around with outdrive gear ratios.

 

[chiefalen]

Re: 3.0LX Rebuild

I stayed away from asking.

You check the compression the right way ?

Don't get insulted ok ?

How did you do it ?

A lot of people are a bit touchy on here lately .

And what kind of gauge did you use.

 

[maxumized]

Re: 3.0LX Rebuild

DJ, good point. Will check into that.



Chiefalen - did another compression check, but this time the engine was cold (60'F ambient temp). I was seeing around 120-130 on all cylinders. Although, it took about 3-4 compression strokes to reach max pressure.

Adding a bit of oil to the cylinders never changed the max pressure, but it did allow the pressure to build in 2-3 strokes rather than 3-4.

Last time I checked, all 4 were under 100 (around 95 or so) when I checked on a somewhat warm engine. Those numbers are what got me thinking about the rebuild in the first place.

Both times I checked with a rented compression test tool (Brand name "OEM"). I followed the procedure referenced in Mercruiser Bulletin 97-25. The only deviation was the first time I did the test, the engine was a little warmer than "room temperature."

Now I'm not sure which test was more accurate. I'm still considering checking the head with compressed air to see if there are any leaks.

 

[maxumized]

Re: 3.0LX Rebuild

Oh, and I should have mentioned that when I come asking for advice, my pride is checked at the door. I don't get insulted. I recognize my knowledge gap in marine power and that's why I'm here!

 

[chiefalen]

Re: 3.0LX Rebuild

You know there might not be anything wrong with that motor.

Maybe all you need is a good tune up and a set of ac plugs. And timed right.

Want to try one last thing, at night pitch black out, start the motor with water to it of course, and see what it looks like in the engine bay.

If you see lightning storm in the bay you know where to start changing in new wires and such.

Good luck, i am trying to help. Just as all the people here.