Questions about 1980 mercury 140 "tower of power" outboard

[Lukelona]

Just bought a 99 Larson 20' bowrider with a 1980 mercury 140 outboard
Story goes, it ran end of last season, but he was having problem reaching normal speeds.
It sat for the winter, I bought it yesterday but we couldn't get it to fire up. Didn't try too hard, just primed it and cranked for a min or so.

Now..... First question- when priming bulb, it doesn't "pump up" and get hard like I'm used to on previous smaller outboard motors. Instead it eventually leaks gas out of center of carb. Is this normal? Or should it pump up hard like I'm used to?

Second question- never had one of these engines so I'm not sure how much work is too much to put into it. It needs a prop, it's banged up and bad shape.
I have a spare Mercruiser SS prop in the shed. Are they the same? Will it fit?
My SS just needs a new hub, but cheaper than buying new prop I guess.

3rd question- the throttle is stiff, and he thinks that cables had to do with not reaching higher speeds last season. It appears they used Original controls to the boat (not positive)
But as stated it has a totally different motor now.
They're quicksilver controls with the fast idle lever and tension adjust knob on front.
I'm not sure how to choose a replacement cable to fit and work properly

Any help appreciated as always, thank guys and gals

 

[Texasmark]

I had an 88.

Bulb doesn't pump up hard, cracked fuel lines, hole in fuel pump diaphragm, carb needle valve not seating due to conical surface damaged or float sticking or sinking.

Prop, see if it fits. If so run it. If happy leave it, if not come back here with some numbers like pitch, mph, rpms, trim positon load, hull type and all that stuff....we know nothing much...name, length, engine make and hp is all, about your boat and your operation of it.

Look at the butterflies. If perpendicular to the venturi the throttle cable is not sticking. If not, remove the throttle cable from the engine and where the center conductor of the cable secures to the engine throttle linkage, move it all the way back by hand. If the butterflies do as stated you have cable problem. If not you need to do a link and sync adjustment inside your engine. If so, get a new set of cables....that year is well old enough to require new running gear.

 

[KD4UPL]

I had a '97 Larson 20' bowrider with a 210 HP V8. I would call the power adequate but nothing special. I would imagine that your boat with 140 HP would "have a problem reaching normal speeds."

 

[Chris1956]

The Mercruiser prop will have the larger hub, and will not fit that inline 6.

The primer bulb is either worn out, or as was suggested, the fuel pump diaphragm has a hole or the carb inlet needles are sticking open. Check it in a day or so , as sometimes the inlet needles stick during storage, but work themselves loose.

You will want to run a 15" pitch or maybe less pitch, to push that boat. Trial and error will determine correct prop,

Remove the wrap cowling and push the throttle forward. Observe the throttle plates in the carbs. At WOT, they should be nearly(but not quite) open all the way.. If not, the throttle cable/linkage needs some attention. I cannot picture the controls you describe, but if they are Quicksilver, they should work.

Sounds like you should take a compression test to see if the motor is worth fixing.

 

[jimmbo]

Fuel leaking out of carb is not normal. Either the float is stuck, is too heavy, not adjusted correctly, or the inlet needle and/or seat are loose, not seating, or contaminated.
The bulb should firm up, but since the carb is leaking...
When you say "having problem reaching normal speeds", what was the WOT rpm?

 

[Lukelona]

Sorry guys, thanks for the help so far!
Update, it stopped leaking gas completely, I got it running and it actually runs great. Bump the key and it doesn't turn twice before it's running. Throttle response is great also
I don't know RPM at wot the guy I got it from wasn't very observant lol he also barely used the boat. He only had it a year and I think he took it out once or twice.
The primer bulb gets hard now as it should.
However, it does appear to have choke plates hooked to a actuator at top of engine. But I haven't seen them move so I don't think it's working. I'll have to figure that out also I guess.

My new issue is the prop will NOT come off the shaft. I've tried hammer and block of wood, tapping and turning into my arms were tired lol tried a little heat on shaft, as well as pb blaster to no avail.
Can't get my hands on a puller so I guess the die grinder is next step lol

Dang was hoping the Mercruiser prop would fit, guess I'll be buying a new one ughhh lol

I found he had the motors trim pin at the highest position, between that and the torn up prop I'm almost positive that's where the speed issue was.
I plan on dropping trim pin down, replacing prop and re-test.

When y'all say experiment with different props, is there a way to do this without buying a bunch of props?

 

[merc850]

Does it have a tach? very important for prop selection - max. rpm should be 5000-5500, the choke is usually activated by pushing in and holding the ignition key or by a button on the control box. The motor should be only on the 2nd or 3rd hole from the transom. When you get a new prop put some anti-corrosion grease on the propshaft to prevent it from seizing on. Whenever I get a used motor I check the gear lube, the wiring, the waterpump and grease any moving parts. There should be a Coast Guard plate in the boat that tells the weight and HP rating you can use this to figure out which prop to use. Sounds like the previous owner was a total loser.

 

[Chris1956]

Tilt the motor full up. Fill the splines of the prop shaft with a good penetrating oil, and let her soak. Now take a 2X4 and pry between the gearcase and prop, on each blade, and see if you can work the prop off. Pry gently but firmly, and they will usually come off.

 

[Lukelona]

Does it have a tach? very important for prop selection - max. rpm should be 5000-5500, the choke is usually activated by pushing in and holding the ignition key or by a button on the control box. The motor should be only on the 2nd or 3rd hole from the transom. When you get a new prop put some anti-corrosion grease on the propshaft to prevent it from seizing on. Whenever I get a used motor I check the gear lube, the wiring, the waterpump and grease any moving parts. There should be a Coast Guard plate in the boat that tells the weight and HP rating you can use this to figure out which prop to use. Sounds like the previous owner was a total loser.

It has a tach but I don't think it's hooked up to the motor. It basically has just enough hooked up for it to run.
P.o was not very bright that's for sure. Now it's my job to get it right. I'm probably going to repower the hull later on but would like to get by with this one for now since it does run great!
The coast guard tag says it's rated up to 175hp.
Most I see online have 120-150 HP outboard.
The hull is a 1999 with this old a** mercury on it lol

 

[Lukelona]

Tilt the motor full up. Fill the splines of the prop shaft with a good penetrating oil, and let her soak. Now take a 2X4 and pry between the gearcase and prop, on each blade, and see if you can work the prop off. Pry gently but firmly, and they will usually come off.

I've had it soaking for 3 days so far. Still stuck. Although I didn't get a chance to try again today.
I'll try the 2x4 trick n see if I can get leverage enough to remove it.
The motor looks pretty good and clean, but damn it seems like the props never been off lol

 

[jimmbo]

The 140 had a WOT rpm range of 5300 - 5800 rpm, 5000 - 5500 was for the 115.
That "old a** mercury" was a very good engine. It is pushing 1.4 hp per cubic inch of displacement. You might have to cut the prop off if gentler methods fail. Cutting thru the rubber hub and then carefully cutting a couple of grooves lengthwise in the splined hub, then using a chisel or a big nut splitter. Heat can work, but then there is a risk of damaging the propshsft seals. A skinny hook puller might be fit down the prop hub and get behind the thrust washer

 

[Lukelona]

The 140 had a WOT rpm range of 5300 - 5800 rpm, 5000 - 5500 was for the 115.
That "old a** mercury" was a very good engine. It is pushing 1.4 hp per cubic inch of displacement. You might have to cut the prop off if gentler methods fail. Cutting thru the rubber hub and then carefully cutting a couple of grooves lengthwise in the splined hub, then using a chisel or a big nut splitter. Heat can work, but then there is a risk of damaging the propshsft seals. A skinny hook puller might be fit down the prop hub and get behind the thrust washer

I've heard nothing but good things about the ol "tower of power" engine...I mean hey if it runs good and is reliable I'll leave it on until I sell it lol in fact,I'd be happy to
I couldn't get it to budge still...Started with the cutting off process after work today.
Got some of it cut, (carefully) and chiseled big chunks off. Then it got dark and wife was yelling for dinner so I wrapped it up for tonight.
Should have it off tomorrow

Anyone know what prop fits this old girl?
That'll be my next step I suppose.
Having trouble finding a site that goes back to 1980 to find the right prop

 

[Texasmark]

I've heard nothing but good things about the ol "tower of power" engine...I mean hey if it runs good and is reliable I'll leave it on until I sell it lol in fact,I'd be happy to
I couldn't get it to budge still...Started with the cutting off process after work today.
Got some of it cut, (carefully) and chiseled big chunks off. Then it got dark and wife was yelling for dinner so I wrapped it up for tonight.
Should have it off tomorrow

Anyone know what prop fits this old girl?
That'll be my next step I suppose.
Having trouble finding a site that goes back to 1980 to find the right prop

I ran a Laser 13+ dia, 19P on my '88 115 on a 17 ? Ranger Fisherman. Excellent marriage. Plenty of places to find props on the www. You can start with Iboats at the top of this page under Boat Parts & Accessories.....in the section go to props, and they even have a tutorial to help you in understanding what makes your prop tick and what does what.

 

[jimmbo]

inline 140 on a 20 footer. You might have to put a 15 in. on there to keep the revs up. 16ft thru 18 ft boats usually take a 17 in

 

[Lukelona]

inline 140 on a 20 footer. You might have to put a 15 in. on there to keep the revs up. 16ft thru 18 ft boats usually take a 17 in

Can you explain further? I've only delt with props a couple times, and that was pretty much direct replacement with ss

 

[jimmbo]

I was saying a 140 on a 20 ft boat, would probably need a prop with a 15 inch pitch in order to get the WOT rpms in the 5300 - 5800 range. In my experience, the 140 on 16 -18 ft boats needed a 17 in pitch prop to run in that rpm range

 

[Texasmark]

Each rig is unique unto itself. Unless identical twins used by identical people, under identical conditions "taint no two de same". So, it's all a crap shoot till you "put the pedal to de metal". Anybody that says otherwise is just spoofing you!

 

[Lukelona]

Ok thanks guys. So is it just an expensive experiment? Buy a prop try it, if not happy, order another? Sheesh I'll exceed the value of the motor after a couple props lol
What pitch would be "standard" for this motor? Preferably around 20' hull?
Is this motor powerful enough for a 20.5' bowrider?

 

[jimmbo]

Mercury didn't ship their engines with a prop, as there is no 'standard prop'. As mentioned each is a custom fit to the boat and intended use. I would suggest a 15 in would be a good place to start. The aim is to prop that engine around 5700 - 5800 rpm, but the range as mentioned earlier is 5300 - 5800 rpm
As for the motor being enough power. You will probably see in the range of 38 - 42 mph. In 1971 the biggest production outboard was a 135, it was used on boats bigger than yours

 

[Texasmark]

Have a prop shop handy? Most will let you test props to find what you want and purchase it from them. Costs more, but in the long run worth every penny you paid. You take the prop, put it on, test it, and get it back off so that if you don't like it there is no damage to it and he can sell it to another customer and find one that suits you. Who knows, the one you find tunes in to your sweet spot, may have been tested by others, who knows how many times yet it is still a "new" prop.

Or if you get a prop and aren't quite happy with it, they can tune if for you if you aren't off all that much....how much depends on the prop and material. Great bunch of guys, give them a try. In Dallas it was James Propeller Service for me.