1952 Evinrude 25 hp BigTwin

[ovnic1234]

I've pretty much had it with this motor. (if I really did you wouldn't be reading this post). All avenues that I know of have been exhausted, I could use some thoughts.

Here's what's been done:
-ignition- new coils and condensers, polished points, new marine plug wires
set points, and new plugs J4J or equivalent. (great spark)
-split the case, new seals top and bottom, between the halves, newer pistons,rings, honed cylinder, and new head gasket, lapped head.
-inspected leaf plates, all is well
-carb- rebuilt at least twice, needles are good.
-set the fuel timing, index mark making contact when tiller handle is in the
"start" region
-installed a Mikuni style fuel pump, pulling off a bypass cover. plugged the
old pressure supply on the intake

It's flooding out, needles are set according to Joe Reeves initial settings after a carb rebuild. Both plugs are equally wet.

There's a lot of pulling, followed by a backfire. A lot of fuel is coming out of the carb throat. It will act like it's going to start, but doesn't. I've tried closing of the high speed and gradually closing off the slow speed to no avail.

I don't get it. Could there be a hairline crack in the carb somewhere. I've tried closing of the high speed and gradually closing off the slow speed to no avail.

 

[tx1961whaler]

Re: 1952 Evinrude 25 hp BigTwin

Is there a cork float in it, or has it been replaced by a plastic one?

 

[jbjennings]

Re: 1952 Evinrude 25 hp BigTwin

The float question is right on.....

I just wanted to mention that on my big twins, I notice that if you choke it for more than one or two pulls and don't open the choke, it will flood. I choke mine and pull the rope. I then open the choke and I pull it until it starts. These big twins suck a heckuva lot of fuel in with the choke closed, moreso than the smaller OMC's of the fifties.

Also, if your metal tipped float needle is good, don't change it out with the neoprene tipped one in the carb kit. They're bad about sticking, whereas the metal ones are usually totally reliable if the fuel is clean.
Good luck,
JBJ

 

[ovnic1234]

Re: 1952 Evinrude 25 hp BigTwin

I have replaced the float, with another cork one. It was an unused, new old stock replacement.

Jbjennnings, I will try your starting procedure this evening. And will try to find the old needle. I've read on here that they are big drinkers, I hope to find out for myself, preferably on the water.

Thanks so much, this forum is a wonderful resource

 

[bigrockets]

Re: 1952 Evinrude 25 hp BigTwin

There is another posting on the forum for a 4HP evinrude where Rick (commander) responded that the cork floats are coated with a varnish or shellac that breaks down with methanol fuels. His suggestion to the poster was to get a new OEM carb kit that has a plastic float. Bits of sissolved varnish in the fuel bowl could be bad for future operation.

 

[ovnic1234]

Re: 1952 Evinrude 25 hp BigTwin

Hello again,

Beautiful day not to be on the water.

Does anyone know the sierra equivalent of OMC part #375792, it's the float. I am looking for the plastic replacement. Couldn't find it here.

JBJennings, you were right on. I goofed the last time I rebuilt the carb. Left the little spring clip off the float and needle. It was stuck nicely in the closed position, while the float was hanging down. Got my dad to mail me an all metal one.

Full on flooding, at higher rpm it pumps fuel out of the bowl vent.

Excuse the rambling, and thanks as always.

 

[steelespike]

Re: 1952 Evinrude 25 hp BigTwin

My guess is the pressure is too high on the pump.
Does it run normally with the fuel line unhooked.
If I'm not mistaken there is an OMC pump that will work.

 

[samo_ott]

Re: 1952 Evinrude 25 hp BigTwin

What did you do with the old bypass cover? Did you drill and tap it? The 35.7 cu in is a common engine into the 60's and a bypass cover with the boss to mount a proper pump on it would be available if you found one. If you determine that the mikuni is an issue.

 

[ovnic1234]

Re: 1952 Evinrude 25 hp BigTwin

I gave my arm a rest and went fishing for a bit.

I've used that mukini style fuel pump on a 55' 7.5 hp Aquasonic, with great success. Don't know why it wouldn't work in this situation.

I'll go try to get it started and try disconnecting the fuel line.

The bypass cover is a replacement from the 60's. So an omc pump will work. I hacked an old fuel pump (early sixties style-no rebuild kit-cracked anyway) to pieces cut the aluminum casting down, tapped a hole for a nipple in the center and bolted it on with the same gasket.

I have some older 50's style fuel pumps w/sediment bowl, I was wondering how serviceable they are. Are they relatively simple to rebuild.

I'll take some pictures of the set-up if it would be helpful.

I still wouldn't mind a plastic float. Although this one looks good.
Anyone know where to get one? marineengine had it by the part number but would it be just another cork one?

Steelespike: higher rpm=fuel pumping out of the bowl vent. Too much pressure makes sense. Thanks Ott as well.

 

[F_R]

Re: 1952 Evinrude 25 hp BigTwin

There is no plastic float for that motor. However, NEW cork floats are coated with something other than the shellac used on the old ones. They look pretty much the same, so it is hard to tell which you have.

 

[1946Zephyr]

Re: 1952 Evinrude 25 hp BigTwin

Forget about it. That motor is junk. Time to get rid of it. I'll give you my address and you can ship it to me.

 

[ovnic1234]

Re: 1952 Evinrude 25 hp BigTwin

Forget about it. That motor is junk. Time to get rid of it. I'll give you my address and you can ship it to me.

Good one, I've seen you post those same words before. Copy and paste. I'll pay shipping. I got a buick 225 out of an evinrude sportsman you are welcome to.

I had a spark plug strip out on the head, knew it was questionable, always careful. Finally over did it. Got the shop down the street putting an insert in.

Stole a working fuel pump off a 58' 35hp lark, tacked it on to the side. If it fixes the issue, I will fork out for a pump that mounts on the bypass cover. can't wait for the pulling to resume.

Take care. Too much time and love invested (and that currency), will carry on.

 

[asdasc]

Re: 1952 Evinrude 25 hp BigTwin

OK, reading this from the start, my first thought is to swap the plugs wires. I don't mean to overstate the obvious, but I have made that mistake myself and was POSITIVE I hadn't. But I had.

The discription of the problem you gave sounds JUST like the symptoms I had.

Good luck!

 

[ovnic1234]

Re: 1952 Evinrude 25 hp BigTwin

If this will help anyone, this is what I've learned.

If your father (whom I love very much) decides to stick his nose in your project and suggest a carb swap. Pay attention. From now on one person, one project. His idea of packing washers were rubber o-rings. I gave him a motor of his own. The carb swap required a change of the the plate of the throttle butterfly valve. Make sure you orient it in the correct position. Take pictures. If you install it upside down, the larger cut out area allows more fuel and air to be picked up from the high speed.

Thank you, steelespike for recognizing that it had too much fuel pressure. I changed out the mikuni to a omc fuel pump. I did this prior to flipping the plate, I am calling it done, although I think the mikuni setup is a cheaper alternative to an omc replacement and might have worked. It's output is comparable from what I've read.

There is little room to under that model's cowling. To mount the fuel pump I had to use a bushing on one of the intake manifold screws (unsure of correct terminology). Behind and to the left of the carb.

jbjennings: thank you, I switched back to an all metal needle, instead of a rubber tipped needle.

Had a great day on the lake yesterday, hard to start at the ramp, but got better as the day went on. I imagine as the new rings break in things will get better (90 lbs each compression)

13'6" boat with 25 hp is a pleasant combination, with two people and too much gear, it jumps on plane very quickly compared to the 18 hp I was running before.

Thank you so much, I started fooling with this motor in March, and am very happy with the results.... finally.

Take care all, thanks again

Attached is a picture of how it is supposed to be, turn it 180 degrees if you enjoy suffering and blisters.

 

[1946Zephyr]

Re: 1952 Evinrude 25 hp BigTwin

Good one, I've seen you post those same words before. Copy and paste. I'll pay shipping. I got a buick 225 out of an evinrude sportsman you are welcome to.

I had a spark plug strip out on the head, knew it was questionable, always careful. Finally over did it. Got the shop down the street putting an insert in.

Stole a working fuel pump off a 58' 35hp lark, tacked it on to the side. If it fixes the issue, I will fork out for a pump that mounts on the bypass cover. can't wait for the pulling to resume.

Take care. Too much time and love invested (and that currency), will carry on.

Ohhhh yea. Others here who are old outboard nuts have too.

Those old Evinrude Sportsmans are good little motors. I had a couple in the past. A '37 and a '46. Those '52 Evinrude BigTwins are awesome too. The oldest of those I had was a '56 though. I just sold a '53 RD Johnson last year that had awesome potential. I think the guy who bought it probably got 'er fixed up by now.

Take good care of that gem.

 

[jbjennings]

Re: 1952 Evinrude 25 hp BigTwin

A pic of the carb and no pic of the motor>????
Glad you got it running!
Happy boating,
JBJ

 

[1946Zephyr]

Re: 1952 Evinrude 25 hp BigTwin

90 psi?? seems kinda low, but its enough to run. Good to hear you got it running. A nice gem like that though, I would strip it down to the bare nuts and bolts and restore it.

Those early Big Twins are real classics and look awesome. I'm rebuilding a Ford 460 right now. Now thar's a rebuild project.

 

[ovnic1234]

Re: 1952 Evinrude 25 hp BigTwin

I'll post some pictures as soon as this crap weather clears out. I'm down in Huntsville, AL where I used to live, remodeling a bathroom.

That 90 lbs number was on a single pull. I shouldn't have posted that number. I was mainly looking for consistency, I had pulled the head to get the insert put in on the lower spark plug hole. Honed cylinders and new rings, it should have higher numbers than that.

It's not that pretty, when I first got it I was going to paint it immediately (nymarine). Getting it to run and run well first, then paint. That's a good winter time project.

I wrote a little contract to myself last night. No boat or motor purchase for one year. If there was someway I could block out Craigslist, like some sort of parental control program with a password, that I learn in a year.

There's at least 5 or 6 project motors hiding in the storage shed.

Rambling, back to tiling, I'll get some pictures up soon. Take care

 

[1946Zephyr]

Re: 1952 Evinrude 25 hp BigTwin

Hey, even when they look ugly, they look awesome. Personally, I think they look better than the old Johnsons. I prefer the old Evinrudes myself. Another one of my favorites is the 1957 Fastwin and 1957 Big Twins. There were no better motors than the old blues. Once my place sells, I plan on hunting down a couple of my favs and restoring them. Right now, I have to focus on my old truck, for when I move.

Can't wait to see those pics

 

[JimS123]

Re: 1952 Evinrude 25 hp BigTwin

Here's my '53. I didnt mess with the fuel pump though. Just rebuilt and restored the gas tank and she runs like a dream. Nothing wrong with the old pressure tanks IMHO as long as they are sealed well.