1974 evinrude 115 hp carb setup

[Nandy]

This motor is not performing as I expected and think the problem is the carbs. With two moderate size adults is not doing over 5200rpm/35mph with a 13 1/4 17 pitch that an evinrude 70 hp does not have problem turning 5500 rpms/30 mph with 4 grown ups in the boat. The top carb has a roller pin that that is hitting the carb assembly. I am not sure that is the way it should be. This pin does prevent the carb to open wot but then, I dont know if it is supposed to. My seloc is mia so I can check. Anyone care looking at their top carb and see if that roller pin is supposed to stop with the carb assembly? I include pictures...

 

[emdsapmgr]

Re: 1974 evinrude 115 hp carb setup

I wouldn't worry about that stop pin. Most OMC engines have enough butterfly shaft tolerance to actually permit the butterflies to over-rotate. Open to level, then continue to rotate, as if to start to close. I'd take the airbox cover off and set the throttle linkage so that at max throttle, the butterfly plates are visually level in the carbs. Suggest you get a factory manual for setting the sync and link. How does the compression check out on the new engine?

 

[Randyg123]

Re: 1974 evinrude 115 hp carb setup

I think the manual (OMC) recommends there be a gap between the pin and the stop when at WOT so you do not bend/break anything. That is, you are not hitting the stop before running out of throttle push. I don't have my manual with me but I think it recommends that a sheet of tracing paper should be used as a 'feeler gauge' to determine the appropriate gap.

But I agree with the comment that it isn't too critical due to the amount of play just so long as you are not pushing too hard past the stop. A proper link-n-sync will make sure both carbs are hitting the stop at the same time (both are wide open) so you are not putting added pressure on one of them. If you are using the Seloc manual, I think it has some errors in the procedure to perform the link-n-sync for that era of engines. At least it did for my 74 135HP. It sounds like, by your question, that you are saying only the top carb is hitting this stop and therefore it seems to me that the carbs are not linked properly.

BTW - I noticed that the linkage between the two carbs (bottom photo) is missing in the photos supplied. I assume that you removed it for the photo or some other reason (while playing with the carbs). Once linked, both carbs should 'hit' the stop at the same time. That's adjusted as described in your manual using the linkage on the bottom carb.

 

[Nandy]

Re: 1974 evinrude 115 hp carb setup

All the linkage is in place. Compression test was 125 or 135 in all of them. I have spark in all plugs.
I took the silencer off and both carbs are hitting WOT when the advanced screw hits the stop. I will decarb this motor asap but I dobt that is it.
The pin is not centered but even if centered I think the top carb pin will be closed to hit the carb body. The lower carb pin clears the carb body ok. I did checked the clearance of the pin afterward and it is not touching the body as stated before here.

 

[iwombat]

Re: 1974 evinrude 115 hp carb setup

The pin should only be in the top carb body and, as stated, it should not actually engage the stop. If you have a stop on both carbs, you've got two top carbs. (Somebody double check me on that, I'm going from memory)

Clearance between the pin and the stop at WOT is roughly the thickness of a piece of good copier paper. The manual gives specifics.

 

[emdsapmgr]

Re: 1974 evinrude 115 hp carb setup

Your compression is fine. These old 135's ran much higher compression than the later crossflows.

 

[Nandy]

Re: 1974 evinrude 115 hp carb setup

There is just one stop but both carbs has the pin. What else should I check? I will be damn if the book is not at the ex..

 

[iwombat]

Re: 1974 evinrude 115 hp carb setup

Make sure that the butterflies are working in unison. i.e. when they're closed they're both closed and when they're open (and parallel) they both are. Use the top carb for reference and adjust the bottom carb to it via the linkage.

 

[Nandy]

Re: 1974 evinrude 115 hp carb setup

They are sync. Being a bit familiar with the 70 hp I know the carbs seems good. Might try to do a decarb now that the rain stopped.

 

[Nandy]

Re: 1974 evinrude 115 hp carb setup

Did a decarb and the motor sounds a lot better and accelerates better and smoothly. Not sure that will make a huge different but Im telling you, the difference is very noticeable.
Put new plugs once I was done with the decarb and had run in regular gas for 15 min. Check the compresion again and it is all 120. I knew it was all one number but I could not remember which. I think I will see some improvement but not much.
we shall see after I use it again.

 

[Randyg123]

Re: 1974 evinrude 115 hp carb setup

The pin should only be in the top carb body and, as stated, it should not actually engage the stop. If you have a stop on both carbs, you've got two top carbs. (Somebody double check me on that, I'm going from memory)

Clearance between the pin and the stop at WOT is roughly the thickness of a piece of good copier paper. The manual gives specifics.

Now you've got me wondering if I have two top carbs on mine. I think they both had stops on them. Will have to check mine when I get home. Hmmmmm..I wonder if that is creating any problems?

 

[CARDNAL98]

Re: 1974 evinrude 115 hp carb setup

just to let you know that the plastic roll pin that is hitting up on your motor and preventing it from going fast. plastic roll pin is what you use to connect both the carbs so that they will excellerate at the same time. that is how you get the high and low speed on water looks like the shaft that runs threw carbs is to short. what you can do is remove the plastic clip pin and put the on the opposite side of the carb braket that you are showing in your pictures. on top and bottum carb then hookup the ajustable rod braket that will connect them so that they will axcellerate at the same time . by doing this it will not hit intake manifold and will let carbs work the way they should and you motor will excellerate and and slow down. this will fix your prob my freinds outboard had the same prob and that is how we fixed it and boat is running gtreat hope this will help.

 

[crb478]

Re: 1974 evinrude 115 hp carb setup

Did a decarb and the motor sounds a lot better and accelerates better and smoothly. Not sure that will make a huge different but Im telling you, the difference is very noticeable.
Put new plugs once I was done with the decarb and had run in regular gas for 15 min. Check the compresion again and it is all 120. I knew it was all one number but I could not remember which. I think I will see some improvement but not much.
we shall see after I use it again.

Let us know how it runs after, I've got a 1975 115 that I also thought would give a little more power than it does. It runs good just not as well as a newer model similar or slightly less hp. I keep playing with it to try to get everything I can out of it.

 

[joeyd50]

Re: 1974 evinrude 115 hp carb setup

Let us know how it runs after, I've got a 1975 115 that I also thought would give a little more power than it does. It runs good just not as well as a newer model similar or slightly less hp. I keep playing with it to try to get everything I can out of it.

Hows it running?

 

[Nandy]

Re: 1974 evinrude 115 hp carb setup

Last year I fiddle with it a bit but I had no improvement. This year my hauling vehicle broke down and I have not been in the water at all. So, no updates...

 

[Craig-]

Re: 1974 evinrude 115 hp carb setup

The roll pin is as it should be.