Cracked block...Replace or upgrade?

[AdellAdam]

I have a 1986 MerCruiser 140. Bought the boat with water in the oil. I figured it wasn't goin to be pretty. Now The questions I have are:

Where can I find a new block without spending a ton of money? GM doesn't have any 3.0L engines in cars. From what I can tell it is similar to the 2.5 Iron Duke, but what's the difference? bore? stroke?

Or would I be better off just upgrading to a 4.3L? What's involved in swapping? I believe the bellhousings are the same between the 2 blocks so I'd be looking at mostly just exhaust manifold changes. Or am I missing something?

I don't have money to spend on a brand new block or engine. Anything I get would be used parts from the junk yard. I only paid $600 for the boat and trailer. And it's in good shape other than this issue.

Any ideas? Thanks guys!

 

[atomb]

Re: Cracked block...Replace or upgrade?

upgrade to 4.3 will require moving of the motor mounts-obviosly doable but i didnt and just replace or search craigslist for a 3.0 . I think youll be hard pressed to find a block maybe ebay but in august your probably not going to find any deals i just went thru this and rebuilt mine but i didnt have to find a block it was just a rebuild. but maybe youll get lucky good luck. You might need new gears for your outdrive someone should correct me if im wrong. Since your only 600 bucks in and sounds like u have a nice boat your way ahead of the game Good luck my 2 cents. In my opinion its hard to be in the water for under 3000 grand unless you have a dingy with a small outboard or someone gifts you a boat. I really want to give you some more positive info but i just went thru this and it was either open the wallet or in my case cc which i will be paying off all winter

 

[ChrisCraftJohnny]

Re: Cracked block...Replace or upgrade?

If you are going to use a car engine from a junkyard. You must install brass freeze plugs. Change to a Marine water pump. Marine Starter. Marine Alternator. Marine Distributor. Marine Carb. Marine Fuel Pump. And change the Cam to a marine grind. Which will not be a drop in procedure, If I know anything about cams.

You may be able to use the old parts from your 3.0. But by the time you hall out some beat 4 banger from the boneyard and then do all this work. You may not have anything that is worth a damn.

I would get a REMANUFACTURED long block from a reputable engine shop. Guys on here rave about Rapido marine. They look low tech (I am in the machining Business) but seem to do good work.

Johnny

 

[Alpheus]

Re: Cracked block...Replace or upgrade?

If you are going to use a car engine from a junkyard. You must install brass freeze plugs. Change to a Marine water pump. Marine Starter. Marine Alternator. Marine Distributor. Marine Carb. Marine Fuel Pump. And change the Cam to a marine grind. Which will not be a drop in procedure, If I know anything about cams.

You arent going to find any GM 3.0 car engines anywhere. No such thing, unless they got an old generator or a forklift layin around with one in it...

If I know anything about cams.

 

[roncoop75]

Re: Cracked block...Replace or upgrade?

Deleted.

 

[tschmidty]

Re: Cracked block...Replace or upgrade?

Well the 3.0 was installed for about 2 minutes in some old novas, but no you won't find it in a junkyard. You can find them online for roughly 1800 or so, Rapid Marine is one. I'd start by tearing down the old one and figuring out why you have water in the oil, where is the crack, etc. You may be able to get away with repairing what you have depending on the condition of the block/heads.

 

[AdellAdam]

Re: Cracked block...Replace or upgrade?

At this point I don't have money for a reman block. I'm hoping that I might be able to braze the crack if it's not too bad and in a not so critical area just to get onto the water this year. I think I'm going to be upgrading to a 4.3L in the end anyway. The boat is a 19ft Glastron and I wanna go fast

I was kind of thinking that GM might have used the 3.0L as an industrial engine. I'll look around at the scrap yard because that guy takes anything metal. There's always weird stuff out by him.

I did notice while looking at remaned engines that the 2.5L has similar casting numbers to the 3.0L. The bore on the 2.5L is 3.875" and the 3.0L is 4". If it comes down to it I might be able to find myself a 2.5L and bore it out. The whole engine will only cost me about $50 so if it doesn't work, it's no big deal.

As far as condition of everything, the head appears to be in great shape and the manifold looks great. The riser is a little rusty, but it doesn't look all that bad. The block seems to be in good shape as well.

I know plenty about cams. You need to replace lifters and springs when you do a cam and that's about it. And that's only if the lifters are worn and the springs aren't strong enough. Sometimes you get away with what's still in there.

The engine had an hourmeter on it. It read 42 hours. Not sure how accurate that is, but if it is accurate it would explain why the boat is so nice.

 

[zbnutcase]

Re: Cracked block...Replace or upgrade?

Well the 3.0 was installed for about 2 minutes in some old novas, but no you won't find it in a junkyard. You can find them online for roughly 1800 or so, Rapid Marine is one. I'd start by tearing down the old one and figuring out why you have water in the oil, where is the crack, etc. You may be able to get away with repairing what you have depending on the condition of the block/heads.

Nope, that was the 2.5/153 used in Novas, not 3.0. And you can forget about the Iron Duke, it is a totally different engine made by Pontiac, the 2.5/3.0 as used in boats, is a Chevrolet engine.

 

[AdellAdam]

Re: Cracked block...Replace or upgrade?

Can anyone tell me if I switch to a 4.3L do I need a different outdrive? or at least different gears?

 

[Bondo]

Re: Cracked block...Replace or upgrade?

Can anyone tell me if I switch to a 4.3L do I need a different outdrive? or at least different gears?

Yes...