1986 Mercruiser 260 (GM 350) Cracked Block?

[LakeMichiganBoater]

Been rehabbing a 1986 Carver Santa Cruz and got the engine running and was testing the cooling system and it leaked a ton. Most were due to loose hoses, but I think I found a crack in the block. Just want to confirm this is not a seam where there should be a gasket that may have failed and it is indeed a cracked block.




Sorry about the pool quality of the photos, had to use my bore scope to see it and capture it. I cant get my head down there to see if it is indeed a crack... but looks like a crack to me.

If it is indeed a crack, what is the best option? Clearly it needs to be pulled, but do I just rebuild it with a new block, shop for used, or use this opportunity to upgrade to something better?

Thanks!!!

 

[Bondo]

Ayuh,.... That's a crack alright,......

Best, easiest fix is another running motor, from another '86 to '95, or a fully dressed '96, 'n up,......
'86 was the 1st year of the 1 pc. rear main seal blocks, 'n '96 was the 1st year for the vortec heads, 'n intake manifolds,....

 

[Scott Danforth]

that is a freeze busted block.

as Bondo stated, get another running motor and swap it.

 

[LakeMichiganBoater]

Yeah... I kinda figured...

Is this a good time to upgrade to FI or something bigger that is a drop in? Or just stick with the same engine, new block?

 

[Scott Danforth]

fuel injection will cost you a bunch of extra money for zero gains. however that is up to you.

if it was me, I would take this time to get a complete post 1996 mercruiser long tail and swap in the boat eliminating all OMC

 

[Bondo]

Yeah... I kinda figured...

Is this a good time to upgrade to FI or something bigger that is a drop in? Or just stick with the same engine, new block?

Ayuh,..... How big is this pile of money, yer trying to get rid of,..??..??..??

 

[kenny nunez]

Summit has 383 Vortec marine long blocks @ $4500.00 with just under 400 hp.

 

[Scott06]

Yeah... I kinda figured...

Is this a good time to upgrade to FI or something bigger that is a drop in? Or just stick with the same engine, new block?

Depends on how much you want to spend

you can get a reman or new long block of same generation, get a 96 and up Vortec 5.7 (needs new intake manifold) and gain 40 hp, go for the 383 that kenny mentioned for 400 hp, of get a new MPI bobtail .

From top to bottom for parts alone those options range from $4k to $20k.
Personally I stick with carbed engines because I dont care if it takes a few seconds to start after sitting and you can fix it with a carb kit and a screw driver...

Either way I would plan on replacing the exhaust manifolds, risers, elbows as they are likely cracked too

MerCruiser 383 MAG STROKER MPI with Freshwater Cooling - 350 hp

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www.michiganmotorz.com

 

[LakeMichiganBoater]

Well I dont want to spend a ton of money, but if I rebuild the engine with a new block I am probably above $1500 as I will probably end up replacing most internal engine parts. So if its under $4000 to upgrade it may be worth it to me. It looks like it may be much more than that.

Any go to places for a new/used 350 block? I am shopping around and they seems to be close to $1000 just for the block, which seems high to me.

 

[Scott06]

Well I dont want to spend a ton of money, but if I rebuild the engine with a new block I am probably above $1500 as I will probably end up replacing most internal engine parts. So if its under $4000 to upgrade it may be worth it to me. It looks like it may be much more than that.

Any go to places for a new/used 350 block? I am shopping around and they seems to be close to $1000 just for the block, which seems high to me.

go to a wrecking yard like LKQ just need to pay attention to the generations of SBC. A marine and truck motor are basically the same thing. That is usually the lowest cost option.

 

[Scott Danforth]

cheapest route would be a running boat with rotten hull and pull the whole assembly.

second cheapest route would be find a running motor in a truck. pull the heads and swap head gaskets to marine. swap out the core plugs to brass. get a new marine circulating pump. buy new exhaust, swap your accessories. inspect the intake. you may need a new intake as well.

In michigan, you should be able to find a rusty truck with a good motor for under $500

 

[LakeMichiganBoater]

Any popular vehicles that had this motor? What year range do i need to be looking for?

 

[Scott Danforth]

Any 1987-1995 GM pickup/van/suburban/Tahoe for your vintage motor

If you want more power, look at 1996-2000 gM trucks and get vortec heads

 

[LakeMichiganBoater]

Any 1987-1995 GM pickup/van/suburban/Tahoe for your vintage motor

If you want more power, look at 1996-2000 gM trucks and get vortec heads

Will that require any new parts to go with the vortec? Or just bolt in?

 

[Scott Danforth]

Will that require any new parts to go with the vortec? Or just bolt in?

New intake (vortec).

 

[Scott06]

New intake (vortec).

was Thinking flywheel size would be different too? If so coupler and starter may not work

 

[Scott Danforth]

was Thinking flywheel size would be different too? If so coupler and starter may not work

The OPs current flywheel and coupler will work on a 96-2000 motor