Logo
FULL SITE MENU

Evinrude 70hp 1995 Oval Port Black top Carbs

P

phillnjack

Regular Contributor
I have a 1995 Evinrude 56 cu in triple with 70hp carbs, these are the newer black top carbs and the motor is the oval port 56 cu in.

originally this motor was fitted with the smaller 60hp carbs from new, but wanting a bit more performance I switched up to the
larger bore/venturi 70hp black tops.
this way am using the identical looking carbs and linkages etc .

But today while cleaning out the carbs I looked at the jets !!!! oh dear wrong jets

it seems the jets in the carbs are wrong for this motor, the jets fitted in these carbs are
top jet in the back plastic is 55D and the bottom/main jet in the bowl is 50D ?????.

what benefit would i get with fitting the correct jets i.e 60D up top and 52D on mains.

would this going up in sizes give me more top end rpm/power.


.
 
I'm not so sure the jets are wrong.

It looks like your carburetors are #0435385 70hp 1992 late production. Those are equipped wirh 55D/50D jets.
Between 1992 and 1995 there have been quite a number of changes to the jetting. 1995+ 70hp cabs (#0437087 and 0439452) are equipped with 60D/52D jets.

I am pretty sure the changes of jets correspond to different shapes/sizes of the venturi and internal passages. So it might not be useful to replace the jets in your carbs with those used in 1995+ carbs.
 
Hi WernerF

How can I tell what the part number of the carbs are ? there does not seem to be any numbers on the carbs that I remember.

These are definitely the large venturi 70hp carbs that are bigger than my 1995 60hp carbs in venturi and bore at the back of the carbs.
 
phillnjack said:
How can I tell what the part number of the carbs are ? there does not seem to be any numbers on the carbs that I remember.
Click to expand...

If there aren't any numbers, you can't I fear. My 1989 carbs had metal tags at the bowl showing some numbers.


phillnjack said:
These are definitely the large venturi 70hp carbs that are bigger than my 1995 60hp carbs in venturi and bore at the back of the carbs.
Click to expand...

No doubt you have 70hp carbs. I thought about minor differences not easily visible. The difference between 50D and 52D wouldn't be visible either.

Either OMC had experimented with jetting on the same carb body from 1992 to 1995 or all the carb bodies differ slightly. In the latter case you should keep the jets.
 
what I am thinking though is the small 50D jet is not letting through enough fuel, likewise the 55D top jet not letting enough air to make the mix right.
this would cause the top rpm range to not be what it should be.

when i changed out the smaller 60hp carbs for these I got an increase in bottom end , and increase in md-range, but no gain at all In the top rpm.

it gets around 6,000 and falls flat no matter what prop, there is no chance of getting near the limiter of 6700 rpm.

comparing the 1992 carbs to 1995 carbs there is nothing different to see everything looks identical.
repair kits are also the part number.
 
phillnjack said:
when i changed out the smaller 60hp carbs for these I got an increase in bottom end , and increase in md-range, but no gain at all In the top rpm.

it gets around 6,000 and falls flat no matter what prop, there is no chance of getting near the limiter of 6700 rpm.
Click to expand...

In theory a 70hp should gain 8% planing speed over a 60hp engine. BUT 6000 rpm is already beyond the peak power operating point i. e. you will lose power with rising rpm. At 6000 rpm your 70hp engine won't produce much more than 60hp. At 6500 rpm there will be as low as 50hp.


phillnjack said:
what I am thinking though is the small 50D jet is not letting through enough fuel, likewise the 55D top jet not letting enough air to make the mix right.
this would cause the top rpm range to not be what it should be.
....
comparing the 1992 carbs to 1995 carbs there is nothing different to see everything looks identical.
repair kits are also the part number.
Click to expand...

The secret in the air/fuel mixture is in the matching of the jets and the position/sizes of the drills in the brass tube. You can't see any difference unless you can look at both carb bodies side by side.
 
You won't see a difference unless you have them side by side. The secret of air/fuel mixture is in the matching of jets and the positions/sizes of the tiny holes in the brass tube.

6000 rpm is already beyond the power peak. Engine torque drops faster than rpm rises. At 6700 rpm your engine won't produce even 50hp.
 
ha ha ha ha ha

you obviously have no idea how much horse power the 56 omc can pump out at high rpm.

who told you the horse power and torque of a omc 56 power drops off at over 6,000 rpm ?

at 6700 rpm the engine hits the limiter, take off limiter and she will carry on producing power an torque until about 8,000rpm.
it dot last too long at 8,000 but will produce over 90hp.

thousands of people are running way over 7 grand with these motors all day long.
 
Back
Top