3.0L 140hp building

[John MD]

I have all but decided to go ahead with a quick tear down of a replacement 3.0L 140HP inline 4 before installation. Been looking at the service manual and it so far seems pretty straight forward. Going to do it myself.

Any pitfalls to watch out for on this motor? What parts need to be replaced that otherwise you might not on another motor...i.e. valve springs, oil pump, rod bolts, water pump, etc.?? Are the pistons, pins typically reuseable? How do the cylinders typically wear and what to look for with this motor?

Any head issues inside the combustion chamber? Where is the best place to get guides, stem seals, valves, bearings, gasket kits, etc? Are you guys using teflon, viton, or something else for stem seals....And are you using them on the exhaust side as well (old 73 140HP)?

Are the cranks nitrited? Do they typically wear evenly only requiring polishing...or require turning with undersized bearings?

Well I know this is quite a bundle of questions. Just looking for good solid building advice as to kind of what to expect.

Thanks in advance,
John M

 

[whywhyzed]

Re: 3.0L 140hp building

I'd mount a starter and compression test it. throw a gauge in the oil gallery while cranking. If it's tests fine, nothing will be improved by tearing it down. Look for rusty oil pan and timing cover that sort of thing.....

do that compression and oil pressure test regardless, and even if you DO tear it down, you'll know what to look for if for example, 1 cylinder was low on comp. ...


and if it doesn't start after it's back together you'll know what you started with for comparisons.

for engines that average 35 hours a year, I doubt it needs freshening even if it is a 73...it was either looked after or it wasn't...and if it wasn't there might be specific issues...like cracks... I'd be shocked if it's worn out.... the crank won't need work unless it's got a spun bearing and a rod knockin'... oil pressure test will show that

I might throw a rear main seal in for insurance... but I might not if it's dry there.

pitfalls?
1. fiber timing gears -easily damaged
2. the price of overhaul kits for these things.... seems the 3.0 has a "marine only" mark up - I couldn't find a kit for less than about $450.. with pistons and such it was getting real close to just buying a new engine...maybe they've come down in price but back when I was shopping it was that...

Is this going in that big Bayliner? You sure you don't want to repower to a V6 or V8 while the engine's out? wow those are big boats for the 3.0

 

[John MD]

Re: 3.0L 140hp building

Ha ha....well the car is small and the boat isn't that big!

But yeah would love to repower bigger, but don't want to do it now. She was an OMC cobra so she still has the small cobra drive. Won't handle a V6 or V8 unfortunately. I would have to switch it all over. The boat was slow to plane. Had to get the weight off the transom. But once up, she would top out in the low 40s on glass. MPH not knots. Good enough for cruising and really good on the gas! I think that boat weighs only 3400lbs or so.

Honestly, I am trying to do this on the cheap. I already did a compression test and found low compression between 2 & 3 cyls. 1 & 4 showed 120. So I am thinking HG. On 2 & 3 I felt compression coming out of adjacent cyl spark plug hole while compression testing the other. I was thinking of just honing the cyls, reusing the pistons, installing new rings, and maybe polishing the crank rod journals and install new rod bearings, for the bottom end. Inspect the mains by just pulling the cap. And on the top, clean it up, relap the valves if they spec along the stem, stick some new stem seals on her, plane the head and pressure test, and reassemble.

My old 3.0 never ate oil so I am of the assumption that the valve guides are pretty durable? What is your take on the water pump in general...leave or replace?

Thanks for the info on the timing gears. I was going to leave them alone.

Best Regards,
John M

 

[whywhyzed]

Re: 3.0L 140hp building

leave the water pump

But once up, she would top out in the low 40s on glass. MPH not knots.

gee, ya might want to GPS that...
My 87 Bayliner 21.5' Capri cuddy with it's 3.0L, did 34mph with a tail wind, fumes in the tank, and me farting as hard as I could

 

[John MD]

Re: 3.0L 140hp building

Its off the depth finder paddle wheel speedo gauge. I haven't GPS'd though. This one is a 2155...88 model. Oh...and WOT, no big wind, but glass. 14 x 13 prop.

Good deal on the water pump.

Best Regards,
John M

 

[achris]

Re: 3.0L 140hp building

Its off the depth finder paddle wheel speedo gauge. I haven't GPS'd though. This one is a 2155...88 model. Oh...and WOT, no big wind, but glass. 14 x 13 prop.

Good deal on the water pump.

Best Regards,
John M

John,

I've just run your numbers through my prop aoa program and I'm sorry but that don't add up....

Unless you have something very unusual going on there the best I can find with a 14 (diameter) x 13 (pitch) prop is about 30 mph, and that's at 5000rpm!!! (assumption is that it has the standard gear ratio in the leg, 1.98:1)....

You have a 140hp (Flywheel) in a 21 foot boat. I have a 220hp (propshaft) in a 20 foot boat and I max out at about 46mph.

Chris...........

 

[tommays]

Re: 3.0L 140hp building

I can fart my way Up to 41 MPH and can hit 39 with the top UP and a full tank and two people

The stingray hull hits 50 MPH witha small person and 8 gallons of gas


Tommays

 

[achris]

Re: 3.0L 140hp building

I can fart my way Up to 41 MPH and can hit 39 with the top UP and a full tank and two people

The stingray hull hits 50 MPH witha small person and 8 gallons of gas


Tommays

That looks like it was built for speed. What the power plant?

 

[John MD]

Re: 3.0L 140hp building

I'll have to GPS it guys......providing of course you keep helping me with this engine! The readings were off the bottom of the transom near center. I wonder if placement could be affecting the paddle wheel sensor while going in a straight line. The depth finder was new. So not reading from the defunct bayliner star wars gauge. This ole Ciera was the smallest of the forward/aft cabins sunbridges. She is relatively light compared to a comparable length celebrity or the like. Sub 3400lbs wet. Tow her with a Honda Pilot. No farting was required. If it is reading wrong, just leave me in my fantasy world as I have had the boat now for 10 years! Tach reading was at 4600 or so. Wouldn't read faster than that. And three blade prop.

Best Regards,
John M

 

[tommays]

Re: 3.0L 140hp building

1995 3.0 merc

I could not see spending 4000 dollars on a 15000 dollar boat so i would have a 4.3 motor that was cramed into to small of space


I like having 36 gallons of fuel on a 4+ mpg BOAT so when i venture out on a 90 mile day i dont have to worry about getting to a marina 1/2 way through


Tommays