Omc v4

[chucklf]

i have a 1983 140 v4 how much can you cut off the heads and still run 93 octane thanks

[terry taylor]

i have a 1983 140 v4 how much can you cut off the heads and still run 93 octane thanks

I did . 0030 thousand but I used the factory thicker head gaskets . The after-market gaskets were thinner and of poor quality thanks .

[chucklf]

if my 140 hp is rated at the crank how much hp is at the prop THANKS MUCH

[terry taylor]

if my 140 hp is rated at the crank how much hp is at the prop THANKS MUCH

HI. I think this is hard to be entirely accurate and would be an opinion only. the 140 bubble back put out good power at the time.Some say it was under rated or stickered ,However they were torque endowed so does this make for horsepower depending on application [boat weight and so on] thanks.

[Ronny Jetmore]

somewhere around 110-115 at prop, some years better (later 1970's heads better) and tuner is supposedly better on a 1977 only for top end. i think yours has the bath tub heads for low octane.

[JWTjr.]

On a propshaft dyno a 1984 140 produced an average of 126 horsepower over a series of pulls. This was done on my stock 1984 Evinrude at SEI back in 1985.

John

[Ronny Jetmore]

the 140 crossflow was that much power in the early 1980's? wouldn't that mean that the late 1970's crossflow 140's put out more like 130-135 then? i didn't think any crossflow v-4 did that much stock.

hey stoker, whats your experience on this?

[chucklf]

I got this 140 off a runabout with a bad transom run compression test 115 to 122o on cyls . I plan to build both carbs new water pump rebuild fuel pump new plugs - wires It is going on a 92 bumble bee bass boat 15 foot 4in boat has a 6inch hudrolic jack plate. boat with 90hp evinrude 2 batteries fuel tank full boat runs 49 mph. do you think this boat will run 60 mph with the 140 THANKS TO ALL YOU BOYS

[Ronny Jetmore]

possibly. if it is a fairly lighter bass boat with a pad. not familiar really with the make of yours. if the boat is loaded down with fishing stuff or people, no i don't see it happening, maybe 55-57. i would think a raker 13 x 20 or possibly 13x 22 would be good on that.

[chucklf]

boat is heavy 1357 pounds with me in it .motor has a wedge on jack plate that i should have removed .with a 22 raker on it only turns 4900 rpm. with 19 steel prop only5100 rpm. i think the wedge is keeping the trim from going high enough to get the rpms i need. it lugs all the time. i cant begin to make a rooster tail. if it would have turned 5800 rpm i think i could have gained 3 or 4 more mph thanks

[Ronny Jetmore]

With that much weight, you need to step down. Plus, based on the rpm you would need to step down anyway. Do a 20 raker. I suspect with the 20 you will pick up enough rpm to put you where you want to be (5500-6000) and yes, you will pick up 3-4 mph.

[JWTjr.]

the 140 crossflow was that much power in the early 1980's? wouldn't that mean that the late 1970's crossflow 140's put out more like 130-135 then? i didn't think any crossflow v-4 did that much stock.

hey stoker, whats your experience on this?

I just made that up for entertainment purposes...:rolleyes:

[Ronny Jetmore]

cuz it militates against everything i have ever heard from omc guys.

no seriously, i wasn't calling your accuracy into question, as you know a lot more about these things than i do, it's just that everyone i have ever talked to that raced and built these things, swears that even in the prime of the bubble back (good heads, intake stuffers) the motor never put out close to 140 at the prop. if that is true, then i would have thought that the later (bathtub head) bubbleback would be even less.

it is simply that something does not add up. if your 1983 (?) was that much h.p. at the prop, then how much for a 1978 140. i have simply never heard a single person that builds and runs these state the motors put that much out.

again, not trying to be a joker, just want to figure out the truth.

[JWTjr.]

cuz it militates against everything i have ever heard from omc guys.

no seriously, i wasn't calling your accuracy into question, as you know a lot more about these things than i do, it's just that everyone i have ever talked to that raced and built these things, swears that even in the prime of the bubble back (good heads, intake stuffers) the motor never put out close to 140 at the prop. if that is true, then i would have thought that the later (bathtub head) bubbleback would be even less.

it is simply that something does not add up. if your 1983 (?) was that much h.p. at the prop, then how much for a 1978 140. i have simply never heard a single person that builds and runs these state the motors put that much out.

again, not trying to be a joker, just want to figure out the truth.


Well...again, I guess that since I dynoed a sample engine at Second Effort, it somehow urges you on to "figure out the truth"? Give me a break. This is the kind of crap that makes people not want to answer questions.

The 1984 140 DID have the tight heads and intake stuffers. They never made a 140 with soft heads and no stuffers. The next engine from OMC with 140 porting was the 115 in 1985, which had (viola!!) soft heads and no intake stuffers.

How much for a 1977/78/79 (best years) 140? Maybe 5-7 hp more.

And...reread my answer. I never said it put out anywhere close to 140 at the prop.

John

[Riverman]

What do you think mine puts out John?

[Ronny Jetmore]

youre an ass

[JWTjr.]

Jeff: probably 155+/- powerhead, 145~150 propshaft (assuming relieved exhaust).

Jetmore: Fine, keyboard cowboy. Say it in person next time we meet.

John

[Ronny Jetmore]

what are you gonna take a bite out of me?

[chucklf]

thought i might put a set of boysen reeds in since i have carbs off will i need to re-jet and do you see any power gain ---also thought about opening exaust with a block from bobs so if it dont help i can plug it back off --------thanks

[Riverman]

Chuck, aftermarket reeds are always a good idea as they are composite and the stock reeds are steel. If the plastic ones fail the engine will eat 'em, the steel ones not so much!

Boysen reeds surely will not hurt any, as for rejetting go up 1-2 sizes and run it and see what the plugs look like. As for relieving the exhaust it won't help power in your case.