1963 Evinrude big twin starting issues

[sms986]

I decided to start a new thread for a new issue. I just rebuilt the big twin and tonight I started it for the first time. I set it in a drum of water and I began with choke on, zero throttle and cranked and cranked it in 5-8 second spurts. It sounded like it was running with the starter motor spinning it, but it wasn't very loud and when I killed the starter the engine would instantly die. Every few cranks I would get a nice loud exhaust backfire. I experimented with choke on/off for a little bit. When choke was on, same thing. It sounded like it was running with the starter motor. When I took the choke off, it did the same thing, but I did not get backfires. At one point, it was cranking/half running, and all of the sudden the engine jolted to a stop, like someone wedged a rod inbetween the piston and head. However, i hand turned it after this and it was free. I cracked the throttle to 1/2 and it started right up. I dropped the throttle down to zero and it stayed on until I killed it. Any suggestions? I'm going to check compression tomorrow. I don't want to start it again until I'm sure Im not going to destroy the motor.

 

[jbuote]

Well, I'm no expert by any stretch, but...

Not knowing anything about your rebuild, and not knowing anything else you've done,
​My first thought would be to check my flywheel key..

When you rebuilt.. Were the tapers clean and smooth?
Good mating surfaces?
​Torqued to spec?

​My 71' 50hp had similar issues in the beginning.. My key was sheared.. Couldn't believe it ran at all.. lol

My gut is thinking, pull flywheel and check key even though you just rebuilt..
At a minimum,
take plugs out and put #1 cyl at top of stroke and see if TDC on flywheel align with pointer on block..

Anyway...
Just a thought from a NON-expert..
​Might not apply to your 63', but..

​Hope it's worth something.. .

 

[oldboat1]

Throttle has to be advanced slightly for starting (fast idle). I'm not sure about "jolting to a stop", but the rest sounds like lean running. You have an adjustment needle for the idle air mix -- sounds like that may need adjustment (initial position about 1 to 1 1/2 turns open.)

The more radical stuff like jolting to a stop may indeed be a timing issue like jboute suggests. I believe the proper torque for your flywheel would be about 105 foot lbs or it can turn on the shaft (shears the key, but more importantly changes the timing).

 

[F_R]

Yeah, proper starting technique is to crack the throttle open a bit for starting. The loud backfire probably was the result of unburned fuel being discharged into the exhaust system. Then a bit of flame comes along and ignites it. Ka-Boom! Get it running and adjusted and it probably will be fine.

 

[sms986]

Okay, so I looked at it a bit closer today. It seemed to start with a little more ease than before. However, I have 60psi in both cylinders. On a fresh rebuild. I hear no grinding, etc. The motor will run once it's on. I'm wondering if my comp is really that bad or I was just scammed with another high quality Pittsburgh pro tool (had to buy a comp. tester because mine is at home.) Anyway, I also noticed fuel squirting out of what seems like the seal between the crankcase and cylinder. This, I don't understand. When the seal between the case and cylinder on a two stroke has an air leak, it does not blow fuel out, it sucks in air and the engine takes off to the moon. However, this fuel leak seems to be coming from the bottom corners where the crankcase, cylinder, and lower unit all come together. I tried to snap pictures of these leaks, but I'm not sure how well of a job I did.

 

[sms986]

Aaaand I can't get them to upload

 

[oldboat1]

bad exhaust housing gasket?

 

[sms986]

It's fuel that is spraying out. Would a bad exhaust housing gasket cause this?

 

[oldboat1]

Depends -- lot of unburned fuel exhausted. If it's obviously clear fuel, sounds like intake manifold to me -- believe there was a spaghetti style seal used, and that might be the issue.

 

[sms986]

It is not leaking from the intake manifold.

 

[F_R]

Okay, so I looked at it a bit closer today. It seemed to start with a little more ease than before. However, I have 60psi in both cylinders. On a fresh rebuild. I hear no grinding, etc. The motor will run once it's on. I'm wondering if my comp is really that bad or I was just scammed with another high quality Pittsburgh pro tool (had to buy a comp. tester because mine is at home.) Anyway, I also noticed fuel squirting out of what seems like the seal between the crankcase and cylinder. This, I don't understand. When the seal between the case and cylinder on a two stroke has an air leak, it does not blow fuel out, it sucks in air and the engine takes off to the moon. However, this fuel leak seems to be coming from the bottom corners where the crankcase, cylinder, and lower unit all come together. I tried to snap pictures of these leaks, but I'm not sure how well of a job I did.

That's where your understanding is wrong. A two-stroke has a partial vacuum in the crankcase when the piston is on it's upstroke, and about 4-5 psi pressure in the crankcase when the piston is on its downstroke. Therefor it will blow fuel and air out of a crankcase leak on every downstroke.

60 psi is too low on a 40hp.

 

[sms986]

Right, but I've seen it way too many times on two stroke motorcycles and such where there is a small air leak around a crank seal, case seal, cyl. Seal, etc, where the result was an uncontrollably high RPM. When the piston is on the upstroke and the vacuum is created, the a/f ratio should be more than lean enough to cause the engine rpm to go up. If the leak in the case is large enough to allow fuel/oil pass through, it should allow much, much more air to pass through under vacuum since air is significantly less viscous than fuel and oil. I don't experience any high idle at all. I'd imagine at lease some would be expected. As a matter of fact, the idle seems much lower than it should be.

 

[oldboat1]

Thinking the carb spray test could apply -- look for rpm change.

 

[sms986]

I will try that this evening. The only thing is I don't want to run this motor any more than I have to because of something is wrong inside that could very well lead to destruction. I did just check this new compression tester on my riding mower, 2 stroke motorcycle, and my truck. I got 60 psi, 60 psi, and 120 psi, respectively. This means one of two things: 1. My outboard, riding mower, motorcycle, and truck are all trashed, or 2. Pittsburgh pro strikes again with unbeatable quality. When I am up home next I will grab my functioning compression tester, but for now I am going to rule out low compression as an issue.

 

[racerone]

" rebuilt "----Means different things.-----The leakage at the joint is a concern.---Were the surfaces cleaned of all old sealer ?----What sealer was used on re-assembly ?---Have to ask---were bearings on the crankshaft properly located on the dowel pins ?-----60 psi is way to low

 

[F_R]

Not disputing your motorcycle experience, but I can tell you that I've seen countless outboards with crankcase leaks. Sure, it does allow air to enter, as well as escape. But runaway would be an unusual symptom. In fact, minor leaks usually show no symptoms other than making a mess. Worse symptoms are lower crankshaft seal leaks that allow water to enter the crankcase and destroy all the bearings. And the owner never knows it is happening until too late. Way, way common.

 

[sms986]

Like I said, I am almost certain that the compression reading was due to a fault comp. Tester. I will recheck it with one that I know works though. Surfaces were cleaned with acetone and all residue of old gasket material was removed beforehand. I added a thin coating of ultrablack to the case mating surfaces before installation. The dowel pins were indeed lined up as well. I primarily build dirt track engines, and I build a whole lot of two and four stroke dirtbike and quad engines as well. I've always used ultrablack on cases and I've never had any issues like this. With bike and quad engines, the cases are pressed around the crank. Bearings pressed into side cases, then the crank goes in. I've always frozen the bearings and crank before installation on these. However, on top and bottom half cases, like this one, and on auto engine builds, I never freeze the crank since the crank is 'clamped" in at the bearings. I had a bit of trouble getting the cases to mate on this engine. It seemed like the torque specs were met but the engine cases were still not completely sealed. I did not go over the torque specs. Could this be the reasoning? At this point, Im thinking that I need to pull the bottom case off and remove the crank from the rods, then freeze the crank before installing the rods and assembling cases.

 

[sms986]

Not disputing your motorcycle experience, but I can tell you that I've seen countless outboards with crankcase leaks. Sure, it does allow air to enter, as well as escape. But runaway would be an unusual symptom. In fact, minor leaks usually show no symptoms other than making a mess. Worse symptoms are lower crankshaft seal leaks that allow water to enter the crankcase and destroy all the bearings. And the owner never knows it is happening until too late. Way, way common.

I understand, and that's why I'm here. I value all of your inputs because one thing I've learned is that every engine is different, and like I said this is my first outboard build. I have no clue how outboards generally act under given circumstances. As a matter of fact when I opened this engine up at first I s*** myself when I saw no air filter. Later on I learned that outboards generally don't have air filters as they are sealed by the covers. This just shows my lack of experience with outboards.

 

[sms986]

I guess what I'm saying is that I know the cases did not mate. I can see that for myself. What I want to know is if I did something wrong when assembling the cases, as well as if the symptoms I described at first are all related to that bad sealing job.

 

[F_R]

Assuming the cases have not been modified, there should be no problem sealing them if you are using new spaghetti and trimming the ends square. I've never used that kind of sealer in this application, so have no opinion on that. Scotch 847 is the correct stuff, but I wouldn't call it a must use brand.

No need to freeze anything. The tapered dowel pins and bearing shells align everything, and the bolts hold it together.