1958 35hp Super Seahorse compression troubles

TLanglitz

Petty Officer 3rd Class
Joined
Jun 20, 2004
Messages
87
I think its been 7 years since I've had this one running. It's an electric start 1958 Johnson Super Seahorse. This motor came with my 16' Richline, and back then it took only points, a new coil and some head scratching to make it push the boat at about 25 mph, which wasn't bad. I remember the last day I ran it ... I had decided the carb needed a rebuild. It was difficult to start. Last night I did a compression test (first one since I've owned the motor), planning to get the boat back in the water soon, and I'm only coming up with about 25 psi per cylinder using the electric starter .. which is cranking very slowly. The motor has been in the weather,(covered much of the time), but I only had the lower unit off for all of this time so the power head should have been sealed up tight. <br /><br />Could the motor have been running before on only 25 psi compression, and that was making it hard to start at that time? I haven't pulled the head yet as I didn't want to open it up until I had a new head gasket in hand. I did tilt the motor so the cylinders were pointing upward and sprayed WD40 into each, and that made no difference in the compression which suggests to me that this may not be a ring or cylinder problem (unless its really severe.)<br /><br />This motor also has compression release, which shouldn't engage when using the electric starter, but I'm not convinced that isn't the problem. I think its strange that both cylinders are that bad, and with similar bad compression in each. Am I just thinking wishfully that this could be a compression release thing, or maybe just a blown head gasket ... or even possibly valves?<br /><br />Thanks in advance for any advice.<br />Tom
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: 1958 35hp Super Seahorse compression troubles

Thats it -- the valves are bad. Probably a broken valve spring or two. Bummer. Tough to find replacements. <br /><br />Seriously, the are no intake or exhaust valves. Its most likely showing such low compression because of the motor spinning so slow. Get the battery up or the starter fixed (gotta do that anyway) and check her again. I have a feeling the numbers will be better.<br /><br />Good luck!
 

alcan

Commander
Joined
Dec 14, 2001
Messages
2,505
Re: 1958 35hp Super Seahorse compression troubles

As Dhadly suggests use a fresh battery. Insead of wd40, soak up the cylenders with seafoam or some other brand of decarbon juice. Your rings may be stuck in the lands. Dhadly was correct your motor does not have intake and exhaust valves as in traditional 4 stroke engines. The compression release does use small traditional style valves. It is unlikly that they would cause the motor not to start. If you suspect this is the problem. remove the actuator rod and smack the valves open and closed with a soft faced mallet. Use the appropreate smack, don,t over do it. Also make sure all the linkage to the compression release is funtioning correctly.
 

TLanglitz

Petty Officer 3rd Class
Joined
Jun 20, 2004
Messages
87
Re: 1958 35hp Super Seahorse compression troubles

No valves? Ok, I just read a little on outboards and now I feel stupid, but if you're right about the slow cranking, its well worth it. lol<br /><br />Thanks for that amazingly fast response, <br />I was cranking the motor using jumper cables from my car directly to the starter ... (The weather wasn't kind to the wiring in the boat.) I may run into town to get the battery charger from my shop and use that instead .. it has a 100 amp boost for jumping. The starter jumped up and engaged the flywheel on the second try, but it definitely seemed weak when it did finally work. I sprayed it down with wd40 before I quit last night. Its not disengaging from the flywheel so I know its not right, but hopefully it will work well enough to crank the motor for a compression test. If not I'll pull it and take it apart tomorrow at work.<br />Tom
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: 1958 35hp Super Seahorse compression troubles

Hummmm...... either the starters a tad weak or theres something else keeping it from spinning freely. Your car battery certianly should have been good enough. I'm sure your jumper cables are in good shape.
 

TLanglitz

Petty Officer 3rd Class
Joined
Jun 20, 2004
Messages
87
Re: 1958 35hp Super Seahorse compression troubles

The jumper cables are new. The car was running at the time also. I connected the positive cable to the only stud on the starter that is there for wiring. I touched the negative to the body of the motor to complete the circuit and crank the starter. <br />Tom
 

TLanglitz

Petty Officer 3rd Class
Joined
Jun 20, 2004
Messages
87
Re: 1958 35hp Super Seahorse compression troubles

I think I'm going out there right now to try something. Last night, when I pulled the plug from the cylinder that I wasn't testing, the motor cranked slow still, but two pops instead of one if you know what I mean. I'm going to pull both plugs to remove all compression and crank it to see if the starter will spin it freely. It seems like it should even if the starter is weak.<br />Tom
 

TLanglitz

Petty Officer 3rd Class
Joined
Jun 20, 2004
Messages
87
Re: 1958 35hp Super Seahorse compression troubles

That was the first time I tried cranking with both cylinders open (plugs and compression tester out) .. The motor cranked fast. I think soaking the starter down with oil last night helped. Also, the starter is now disengaging from the flywheel every time. The compression now??<br />100 on the top and 105 on the bottom! Good enough?<br />I think I'll still pick up some seafoam tomorrow and soak the cylinders with it. It can't hurt.<br />Thanks to all for the help. <br />Tom
 

NathanY

Commander
Joined
Mar 16, 2002
Messages
2,408
Re: 1958 35hp Super Seahorse compression troubles

That is great compression on that old motor. Your compression will go up a little when the motor is warm.
 
Top