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1987 omc 3.0 L

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widi59

Member
I'm rebuilding a 1987 Cobra 3.0 engine for a winter project. Valves, springs, pushrods, piston rings and bearings all are readily available at reasonable prices. I'm replacing the pistons .020 OS. Got a new set on ebay at a reasonable price compared to what the standard prices are, but still too high in my opinion.

The connecting rod dimensions seem to be a closely guarded secret. Can anyone tell me what the exact rod length is? and, width at the crank pin journal? I'm hoping a standard sbc 5.7", 2.10 journal, pressed wrist pin rod will work?
 
Re: 1987 omc 3.0

The connecting rod dimensions seem to be a closely guarded secret. Can anyone tell me what the exact rod length is? and, width at the crank pin journal? I'm hoping a standard sbc 5.7", 2.10 journal, pressed wrist pin rod will work?
Click to expand...

Ayuh,... Why not just have the originals resized at a Machine Shop,..??

Your already having the block bored,... Resizing the rods ain't very expensive...
 
Re: 1987 omc 3.0

bondo said:
Ayuh,... Why not just have the originals resized at a Machine Shop,..??

Your already having the block bored,... Resizing the rods ain't very expensive...
Click to expand...

I'm keeping the original piston/rod assemblies to sell on ebay for $100 per assembly. What goes around, comes around.
 
Re: 1987 omc 3.0

off the top of my head no. but i will look into my books and see if i can find it after i dig my wifes car out of the snow so she can go to work, and then i have to get the kids up for school and out the door.

Maybe around noon time i can get to the books and have a look see.

Or maybe someone else will look it up for you and post it today.

Oh yea your welcome i didn't know you already saw the free d/l for sure i won't ever put it up again.
 
Re: 1987 omc 3.0

I'm keeping the original piston/rod assemblies to sell on ebay for $100 per assembly.
Click to expand...

Ayuh,... a Hundred a piece,..?? Used,..??

That's funny,... No, Hilarious....

I wouldn't pay a Hundred for all 4...
 
Re: 1987 omc 3.0

I wouldn't either. But that's what these jokers on ebay are asking.

New= $150 for one rod and $150 for one piston.

A used assembly is a bargin at 100 bucks!

That's what happens when "M" is the prefix/suffix.
 
Re: 1987 omc 3.0

widi59 said:
I'm rebuilding a 1987 Cobra 3.0 engine for a winter project. Valves, springs, pushrods, piston rings and bearings all are readily available at reasonable prices. I'm replacing the pistons .020 OS. Got a new set on ebay at a reasonable price compared to what the standard prices are, but still too high in my opinion.

The connecting rod dimensions seem to be a closely guarded secret. Can anyone tell me what the exact rod length is? and, width at the crank pin journal? I'm hoping a standard sbc 5.7", 2.10 journal, pressed wrist pin rod will work?
Click to expand...

Well I guess I'll just have to answer my own question.

No, a sbc rod will not work. SBC big end rod width = .940. OMC 3.0 big end rod width = 1.029. The OMC rod is also chamfered on both sides of the big end.

If you run across older 3.0/140 engines, buy em up and part em out later. You'll do better than investing in the stock market by a long shot. Especially the blocks, seems like people crack the blocks faster than they could make them.
 
Re: 1987 omc 3.0

I have the 140 in my boat right now. You sitting down ?

My 2.5 went i bought the whole boat, bad drive, sitting on the trailer for 400 bucks cash.

The idiot had the flapper blocking the exhaust . When i stripped the boat down, i found it.

Got rid of the hull and still have most of the pieces.

So what i would recommend is getting a good running 140 drop it in the boat and be done with it.

If you must rebuild your block then go 30 thousand over, complete package kits are available.

Oh yea if you found any parts such as connecting rods not marked m please post the site.

See the 140 / 30 was never installed in a auto. Some bobcats, forklifts, and postal trucks yes.

But then again it was not a 3.0 it was a 2.5.

There is only one machine currently using a 3.0 marine engine.

So i will throw this out to the world to reply to. Just for fun what machine not manufactured, in great numbers but most people will have seen in use. And most people will know the name.

What machine would it be ?
 
Re: 1987 omc 3.0

The Zamboni model 525
All other Zamboni models are Ford powered, including the most popular 520
Olympias are GM powered, but I don't know if they use the 3.0 or not.
 
Re: 1987 omc 3.0

Must be one fan-tastic hull to be worth rebuilding the 3.0. Are you really ready to put 2 grand (or more) into a rebuild? Is the engine seized up or otherwise not running that it has to be rebuilt? I don't recommend any do it yourself kind of engine reconditioning. Have you gotten an estimate from the machine shop yet? If they are anything like the ones around here, they are probably not too interested in a one time job doing a boat engine. They are busy doing work for dealerships and repair shops with far more volume. They'll put it in the corner and get to it when they are darn good and ready, and every time you call asking how much longer they tack on another week. When you get fed up and threaten to come pick it up whether it's done or not they suddenly find time to do it as fast as they can. I've been down that road enough times. If you absolutely MUST have a rebuilt engine, get one that is already done. There must be a lot of 1986 vintage boats around your parts that are in good condition that can be had for 2 grand.
 
Re: 1987 omc 3.0

http://www.michiganmotorz.com/base-marine-engine-19672010-replacement-p-67.html

This is the way to go new, upgraded flywheel, coupler and if you want another 100 for the dist.

The have reman. 1600 use the old stuff if you want.

So guy is going to rebuild, ganna go with a new mani ? What else is going to be new ?

This is my 4th year with my 140 86' vintage. Runs great.

400 dollars for the boat, trailer, that went under my 76' arrow glass bowrider.

Second boat i got, i was looking for a trailer and found one for 300 bucks , i had to take everything.

Funny how life is.

Then i turned around and sold the trailer under the bowrider for 300 bucks.
 
I bought this 3.0 engine fully dressed 3 years ago for 100 bucks. Bought it for spare parts for my 3.0 as the year and model are the same. It had a burned intake valve and broken 2nd compression ring.
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For "something to do" I want to rebuild it. Who knows, it might take 3 more years or never.
*
Initial investment, $100.
Four new "quicksilver" GM pistons .020 OS, paid $70.
Full set of moly rings .020 OS, paid $40.
Four new "quicksilver" GM connecting rods, paid $75.
Four 1.6 high performance exhaust valves, paid $40.
Four 1.94 high performance intake valves, paid $30.
New valve springs, caps*and locks, paid $50.
Machine work $?? $etc. $etc. $etc. $etc. $etc.
*
Yeah, I have a little money "sunk" into the project and it's alot of fun just learning all the in's and out's of this unique little four banger!
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*
*
*
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Re: 1987 omc 3.0

chiefalen said:
http://www.michiganmotorz.com/base-marine-engine-19672010-replacement-p-67.html
*
This is the way to go new, upgraded flywheel, coupler and if you want another 100 for the dist.
*
The have reman. 1600 use the old stuff if you want.
*
So guy is going to rebuild, ganna go with a new mani ? What else is going to be new ?
*
This is my 4th year with my 140 86' vintage. Runs great.
*
400 dollars for the boat, trailer, that went under my 76' arrow glass bowrider.
*
Second boat i got, i was looking for a trailer and found one for 300 bucks , i had to take everything.
*
Funny how life is.
*
Then i turned around and sold the trailer under the bowrider for 300 bucks.
Click to expand...
*
Try Pertronics Flame Thrower electronic ingition with matching flame thrower coil. (coil runs on 12 volts, you'll need to unhook the resistance wire and tape it off) Super Stock plug wires (copper won't work). Bosch Platinum dual ground electrode spark plugs. Run 93 octane and set the timing 4 BTC. I run 20 miles up the lake at WOT and she never skips a beat.*Points are ok if set properly, for about a day.
*
Oh, and unhook that stupid shift interupter switch. It's more trouble than it's worth. Going in gear will be no trouble. Coming out will be hard so just slow down and*allow for that when you're under way. Set the idle down as low as she'll run.***
*
*
*
 
Re: 1987 omc 3.0

my esa has been unhooked a week after i got the boat. My idle is 600 helps.

I love the points. Want to spend money on hi tech coil and wires and dist thats ok with me.
 
Re: 1987 omc 3.0

chiefalen said:
http://www.michiganmotorz.com/base-marine-engine-19672010-replacement-p-67.html

This is the way to go new, upgraded flywheel, coupler and if you want another 100 for the dist.

The have reman. 1600 use the old stuff if you want.

So guy is going to rebuild, ganna go with a new mani ? What else is going to be new ?

This is my 4th year with my 140 86' vintage. Runs great.

400 dollars for the boat, trailer, that went under my 76' arrow glass bowrider.

Second boat i got, i was looking for a trailer and found one for 300 bucks , i had to take everything.

Funny how life is.

Then i turned around and sold the trailer under the bowrider for 300 bucks.
Click to expand...

A new mani?

Remove riser and block exhaust and water jacket with flat plate and gasket. Hook up 230 F water to inlet with drain cock open. When manifold get up to temperature, throttle back on drain cock and bring pressure up to 20 psig. Watch intake and exhaust ports. If it doesn't leak, highly unlikely it's going to leak. Same for the block
 
Re: 1987 omc 3.0

chiefalen said:
I have the 140 in my boat right now. You sitting down ?

My 2.5 went i bought the whole boat, bad drive, sitting on the trailer for 400 bucks cash.

The idiot had the flapper blocking the exhaust . When i stripped the boat down, i found it.

Got rid of the hull and still have most of the pieces.

So what i would recommend is getting a good running 140 drop it in the boat and be done with it.

If you must rebuild your block then go 30 thousand over, complete package kits are available.

Oh yea if you found any parts such as connecting rods not marked m please post the site.

See the 140 / 30 was never installed in a auto. Some bobcats, forklifts, and postal trucks yes.

But then again it was not a 3.0 it was a 2.5.

There is only one machine currently using a 3.0 marine engine.

So i will throw this out to the world to reply to. Just for fun what machine not manufactured, in great numbers but most people will have seen in use. And most people will know the name.

What machine would it be ?
Click to expand...

Melted flapper indicates lack of cooling and elevated exhaust gas temperature.
 
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