correct prop for 74 mercruiser 140hp

[Scott Danforth]

Most I ever got out of a 16-1/2 foot light hull with a 3.0 was 40 mph

If you want more too end, you need a different motor than a 3.0

 

[Chevyls6]

Yeah im mostly happy with the performance of the 4 cylinder. Just wish it ran a little smoother but for a 4cyl with no balance shaft thats probably asking too much.

 

[Scott Danforth]

Yeah im mostly happy with the performance of the 4 cylinder. Just wish it ran a little smoother but for a 4cyl with no balance shaft thats probably asking too much.

It's a forklift motor. Not the smoothest running one out there

 

[Texasmark]

You could stick a good old laser 2 on there, if you find a good used one.

I wouldn't recommend that......too many changes to prop specs.....if the same pitch might load him down too much......but the ports would help his hole shot even if his top end wound up suffering.....saying this since he said he has one shot to get it right.

 

[QBhoy]

I wouldn't recommend that......too many changes to prop specs.....if the same pitch might load him down too much......but the ports would help his hole shot even if his top end wound up suffering.....saying this since he said he has one shot to get it right.

Not sure I mentioned pitch there Texas. But generally a laser 2 like for like with the ally same pitch…will not have a detriment on rpms and can even raise rpms due to more lift and speed given. It’s also a smaller diameter in that size…to the ally black max. As we all know. There ain’t no rules for props though

 

[Chevyls6]

I found an oe replacement prop on ebay that says its a stainless laser 2 but its painted black like an aluminum? Its a 13 7/8x21 with the same part number as my old prop.

 

[QBhoy]

I found an oe replacement prop on ebay that says its a stainless laser 2 but its painted black like an aluminum? Its a 13 7/8x21 with the same part number as my old prop.

Be unusual to paint a stainless laser 2 perhaps. If it’s the same part number as your old prop. Are we saying your old prop is a laser 2 and stainless ? Or are we thinking that the one for sale isn’t a laser 2 Perhaps ? A laser 2 will have a different part number from any other prop, certainly.

 

[Scott06]

Be unusual to paint a stainless laser 2 perhaps. If it’s the same part number as your old prop. Are we saying your old prop is a laser 2 and stainless ? Or are we thinking that the one for sale isn’t a laser 2 Perhaps ? A laser 2 will have a different part number from any other prop, certainly.

I found an oe replacement prop on ebay that says its a stainless laser 2 but its painted black like an aluminum? Its a 13 7/8x21 with the same part number as my old prop.

Not unusual to see old demo props on ebay that are SS and painted, usually an obnoxious color so no one will steal them...

 

[Scott Danforth]

I bought a bunch of SST props 20 years back because they were black and no one knew what they were

 

[QBhoy]

I bought a bunch of SST props 20 years back because they were black and no one knew what they were

To be fair now…I think I have it in my head that Yamaha make some stainless props currently, that they paint for some reason

 

[Chevyls6]

The prop i broke is definitely aluminum. I think the ebay one may be in the wrong box. Sure was a lucky find after searching laser 2. Picked it up for $45 new old stock.

 

[QBhoy]

The prop i broke is definitely aluminum. I think the ebay one may be in the wrong box. Sure was a lucky find after searching laser 2. Picked it up for $45 new old stock.

That’s a bargain. Is it the older or newer type ? Easily told by the vents it has. Older has the square always open vents..newer has the round pvs vents that can be capped or incremental.

 

[Chevyls6]

Not sure what you mean by vents. It doesnt seem to have any holes by the blades. box says feb of 1991 if that helps.

 

[QBhoy]

Not sure what you mean by vents. It doesnt seem to have any holes by the blades. box says feb of 1991 if that helps.

So it will either have the older square type or the newer round type. See pics below. If it doesn’t…I’d be worried that it wasn’t a laser 2 at all !

 

[Chevyls6]

Yeah its definitely not a laser 2 then. Just in a mismarked box

 

[QBhoy]

Yeah its definitely not a laser 2 then. Just in a mismarked box

That’s a shame. Still likely a good buy…if she’s in good shape and a genuine merc prop.

 

[Chevyls6]

That’s a shame. Still likely a good buy…if she’s in good shape and a genuine merc prop.

Yeah its a real merc prop same part number and everything. Aluminum is ok for me since i dont want to break my gearcase the next time i hit something.

 

[Texasmark]

And the name is cast into the barrel so there is no guessing, regardless of the color

 

[jimmbo]

In the early 70s the 140 MerCruiser had a WOT range of 3900 - 4300 rpm

 

[QBhoy]

Yeah its a real merc prop same part number and everything. Aluminum is ok for me since i dont want to break my gearcase the next time i hit something.

Technically that should be unlikely these days. Gone are the older days of fixed hard splined to shaft stainless props. These days they have a sacrificial hub kit in them, that is designed to break, in the event of this. Wouldn’t let this put you off.