Old Merc. 3.0L not 140hp?

[bill 22]

Recently in a thread about performance of an old Merc. 3.0L, 140hp. It was posted that the old 3.0L are not really 140 horse power (maybe 115-120hp). I guess MerCruiser over rated the horse power? At sometime they rated them at 130hp, now the new 3.0L is 135hp.

1. What did they change on the engine to get the horse power back up to 135hp?

2. Besides a complete and detailed tune up, is there anything I can do to increase the horse power of my 1985 3.0L?

I am not a pro but I think I am good do-it-yourself guy.

Engine: 1985 MerCruiser 3.0L, 140hp
Model: MCM 140
SN: 6922598
Outdrive: MerCruiser

Thank you,

 

[achris]

Re: Old Merc. 3.0L not 140hp?

Recently in a thread about performance of an old Merc. 3.0L, 140hp. It was posted that the old 3.0L are not really 140 horse power (maybe 115-120hp).

That depends on where/how the rating is taken. Some engines are rated as Horsepower at the crankshaft without driving any accessories (like alternator, water pump, fuel pump, etc). Some are rated at the crankshaft WITH all the fruit attached, and later Stern drive makers rated them at the prop shaft.

I guess MerCruiser over rated the horse power? At sometime they rated them at 130hp, now the new 3.0L is 135hp.

1. What did they change on the engine to get the horse power back up to 135hp?

2. Besides a complete and detailed tune up, is there anything I can do to increase the horse power of my 1985 3.0L?

1. I believe it is just tweaks to the carb jetting and timing curves.
2. You could do a lot to the basic engine and have it produce as much horsepower as you like. What suffers is the longevity of the engine. Merc are now offering EFI on those engine, and in the development process they upped the output, I think to about 155hp, but the engine just didn't stay together too long.

Chris.....

 

[Bondo]

Re: Old Merc. 3.0L not 140hp?

Recently in a thread about performance of an old Merc. 3.0L, 140hp. It was posted that the old 3.0L are not really 140 horse power (maybe 115-120hp). I guess MerCruiser over rated the horse power? At sometime they rated them at 130hp, now the new 3.0L is 135hp.

1. What did they change on the engine to get the horse power back up to 135hp?

Ayuh,... It more about the method of testin', 'n Marketing...
The 3.0l has changed very little in the last 40 years...

If ya want More horsepower,...
Sell yer boat, 'n buy the 1 you Really want...

 

[bill 22]

Re: Old Merc. 3.0L not 140hp?

achris,

OK..I can see that how they take the rating would make a BIG difference.

Thanks,
Bill

 

[Monterey10]

Re: Old Merc. 3.0L not 140hp?

Digging through the specs, they did list that motor at less HP early. Later, it was pushed up to 140. I cant say what they did to the carb, manifolds or cams to change it.

 

[bill 22]

Re: Old Merc. 3.0L not 140hp?

Bond-o,

Yes, a new boat could provide more horsepower. I am not looking for a miracle that would give a 4 cylinder engine some huge boost in hp. I know there is not one out there. I am looking to you the experts to find out if I can get my engine from 115hp to 135hp with some kind of modification (new head, new timing, electronic ignition, new intake/exhaust manifold…).

From what you’re saying “3.0l has changed very little in 40 years.” It sounds like NO. Whatever hp this engine is making 115 or 120 that is what I got.

Thank you,
This is a great place to get the answers to all the boating question us do-it-yourself guys have.

 

[Bondo]

Re: Old Merc. 3.0L not 140hp?

Bond-o,

Yes, a new boat could provide more horsepower. I am not looking for a miracle that would give a 4 cylinder engine some huge boost in hp. I know there is not one out there. I am looking to you the experts to find out if I can get my engine from 115hp to 135hp with some kind of modification (new head, new timing, electronic ignition, new intake/exhaust manifold…).

From what you’re saying “3.0l has changed very little in 40 years.” It sounds like NO. Whatever hp this engine is making 115 or 120 that is what I got.

Thank you,
This is a great place to get the answers to all the boating question us do-it-yourself guys have.

Ayuh,... Whatever yer horsepower ratin' is, from whichever method used to proclaim such,....

Any less than a minimum 20hp, Increase can't even be felt, much less appreciated...

Hence, my comment....

There just ain't another 20hp to be found in a 3.0l...

 

[bill 22]

Re: Old Merc. 3.0L not 140hp?

A guy at the local mercuiser parts counter said no larger engine (straight 6 cylinder or V6) could be swapped in for my 3.0L and work with my outdrive. Is this true? He said the gear ratio & bolt pattern are too different to make it work.

 

[Bondo]

Re: Old Merc. 3.0L not 140hp?

A guy at the local mercuiser parts counter said no larger engine (straight 6 cylinder or V6) could be swapped in for my 3.0L and work with my outdrive. Is this true? He said the gear ratio & bolt pattern are too different to make it work.

Ayuh,... Yes, the gear ratio is different....

Donno where he's talkin' 'bout a different bolt pattern...
While there are differences, most can be overcome...

 

[Tail_Gunner]

Re: Old Merc. 3.0L not 140hp?

There is a lot of beauty in that old 3.0. Great econ 30mph all day long real easy to maintian..cheap...Just like cars the answer to your question is to run lower gears..the 15p prop for sking along with tabs...and the 17 for running around. After that call it a day

 

[fishrdan]

Re: Old Merc. 3.0L not 140hp?

Newer 3.0's use several different parts to bump the HP, high flow head and matching manifold, increased compression ratio (something like 8.5-1 up to 9.2-1), electronic ignition - better timing curve.

I don't think any of these are going to be cheap or easy ways to bump the HP of an old "140HP".

 

[86 century]

Re: Old Merc. 3.0L not 140hp?

Make sure it's tuned properly and prop puts it in the upper part of the wot spec.
Those little 3.0l will do most anything but go fast.

 

[bill 22]

Re: Old Merc. 3.0L not 140hp?

There is a lot of beauty in that old 3.0. Great econ 30mph all day long real easy to maintian..cheap...Just like cars the answer to your question is to run lower gears..the 15p prop for sking along with tabs...and the 17 for running around. After that call it a day

Yes, I can see the beauty in the “kiss” theory, Keep It Simple! They are an easy engine to work on and are easy at the pump as well.

I plan to get some smart tabs this spring to help with the holeshot. I had a 15p prop and sold it because I thought it was too slow. Now I could kick myself for selling it. When I sold it I did not have many friends that slalom skied. Now that I have more and heavier friends that slalom I really could use that 15p.

Actually that is the only reason I have been asking questions about the horsepower of the 3.0l. I want the get slalom skiers up out of the water faster. For now this old 140 is what I have, I’ll enjoy it and make the best of it.

Thanks to everyone for your input.

 

[achris]

Re: Old Merc. 3.0L not 140hp?

Yes, I can see the beauty in the “kiss” theory, Keep It Simple!

The last 's' stands for 'stupid'... .. Keep It Simple Stupid....

They are an easy engine to work on and are easy at the pump as well.
I plan to get some smart tabs this spring to help with the holeshot. I had a 15p prop and sold it because I thought it was too slow. Now I could kick myself for selling it. When I sold it I did not have many friends that slalom skied. Now that I have more and heavier friends that slalom I really could use that 15p.

Actually that is the only reason I have been asking questions about the horsepower of the 3.0l. I want the get slalom skiers up out of the water faster. ....

Use a prop with ventilation slots, like a Laser II or a High Five... You will be stunned just how quickly you'll pull those guys up with one of those props.

Chris.......

 

[bill 22]

Re: Old Merc. 3.0L not 140hp?

Use a prop with ventilation slots, like a Laser II or a High Five... You will be stunned just how quickly you'll pull those guys up with one of those props.

Thanks for the tip, but I have ventilation holes in my Turbo 1, 14 1/4" x 17p x 3.

Bill

 

[LilRedNeckGirl]

Re: Old Merc. 3.0L not 140hp?

There is a lot of beauty in that old 3.0. Great econ 30mph all day long real easy to maintian..cheap...Just like cars the answer to your question is to run lower gears..the 15p prop for sking along with tabs...and the 17 for running around. After that call it a day

the 3.0 will also, depending on what your looking for, preform well with a 21 pitch. We run twin 3.0's with a 13.5 X 21 on them. our hole shot sucks, @ no water sking, But for fishing, tubeing, knee boarding, long river runs, etc, we get a better cruise speed vs engine speed, @ 25 foot boat, cruises at 3000 rpm doing 25 mph on the gps. fuel economy takes us near 100 miles on the river over the weekend, burning about 25/30 gallons of fuel depending on the load in the boat.

 

[achris]

Re: Old Merc. 3.0L not 140hp?

the 3.0 will also, depending on what your looking for, preform well with a 21 pitch. We run twin 3.0's with a 13.5 X 21 on them. our hole shot sucks, @ no water sking, But for fishing, tubeing, knee boarding, long river runs, etc, we get a better cruise speed vs engine speed, @ 25 foot boat, cruises at 3000 rpm doing 25 mph on the gps. fuel economy takes us near 100 miles on the river over the weekend, burning about 25/30 gallons of fuel depending on the load in the boat.

That's all well and good, but you need to make sure you are still running the engine at the recommended revs at WOT... NO EXCEPTIONS!!! For a 1985 140 the max revs must be between 4200-4600 RPM... Any less than that and you are overloading the engine, regardless of the engine speed. Here's another tip: Running a prop one size SMALLER than 'required' gets you up into the very top end of the rev range AND does not burn any more fuel than a prop one size bigger, for the same boat speed....

Chris......

 

[LilRedNeckGirl]

Re: Old Merc. 3.0L not 140hp?

overloading the engine, lol. so you buy a GM car with a 3.0. put two fat girls and some luggage in the trunk, and your overloading it? maybe in a sence, but engines are ment to handle a load. adjust the trottle you give on the start, and once up on plane, let the engine cruise at a comfortable pace.
i dont have a degree in mechanics, but after running gasoline engines for decades, i know enough to say, an engine run at a mid range rpm, will run fine, last longer, and require less repair then one run wide open every time you get on the drivers seat.
3000 / 3200 rpm has us up on plane, well within the speed range that keeps us skimming along with low resistance against the water. with two engines running, we are at what seems to be an effortless pace for the boat. increasing the engines to wot isnt nessessary for our type of running.
Its almost humorous to hear you say that less then wot is too much load on the engines. thats like saying less then floored is bad on your car, when all data say just the oppisite, @ mid range,. in the power curve, maintaining speed and momentum, is the best overall for fuel economy and ease of operation on the engine.

 

[LilRedNeckGirl]

Re: Old Merc. 3.0L not 140hp?

In regards to the starting post, HP rateing changes to the 3.0's
ive bought many vehicles, and nearl every one, has been made a year earlier then the "titled age".
I see hp rateings the same way. Its all sales hype.
The bottom line, if you need muscle, dont buy a 4 cyl with a rateing under 150 hp. If you want fuel economy, dont buy a big V8.
Past that, if the boat/ car/ truck does what you intended it to do, if it runs without major issue, if it is origional equipment from the MFG, then what is the worry about what the year or HP rateing is?
My boat is an 1985. it was built in 1984. my engines ate twin 3.0's rated at 140. are the rateings accurate? who cares ! it runs, it preforms as i would expect a twin 4 cyl to do, and it has minor issues that come with any boat, any engine.
Dont sweat the small stuff. Get out there and enjopy the boat....

 

[achris]

Re: Old Merc. 3.0L not 140hp?

... Its almost humorous to hear you say that less then wot is too much load on the engines. ....

Which I never said!

But again you misinterpret my post. Unlike a car, a boat has fixed gearing. Once you put a particular prop on, that's it, that's the load the engine will see THROUGHOUT THE REV RANGE, not just at WOT. If you are using a prop that is too big, it's too big for whatever throttle position you 'cruise' at, not just WOT. It's like cornering in a car in third gear, or taking off from the lights in second... Like not changing down to negotiate a hill....

As for lasting longer with a big prop on... Don't make me laugh!!! Go out and ride a push bike with fixed gearing. Which one would do you think you'd last longer on, one with high gearing that requires less revolutions, but more effort per revolution, or one with lower gearing, needing more revolutions, but less effort per revolution? I know which one I would prefer, and your boat engine is exactly the same!

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

Just one last comment... Why do you think manufacturers even specify a recommended rev range? It's to do with longevity, economy, drive-ability and reliability....