Compression Release Valve 1957 35 hp

[R. Bushie]

I have purchased a 1957 35 hp Evinrude that has Compression Release Valve system that the previous owner has disconnected and am planning to rebuild this motor. In doing a compression check #2 cyl. has low compression. Could this be due to poor seating of the Compression release valve? The engine's general appearance leads me to believe it had low hours and had been cared for. At this point I have not removed the head to do a further inspection. Is there another head that will fit this engine that does not incorporate this "valve" system? This is an electric start model and only in emergency would I use the manual start mode that the Compression Release Valve is associated with. To my limited knowledge base I'm of the opinion that being disconnected (as is) could lead to poor seating of the Valve and a compromise to compression. Again, is there an alternate head that will fit this engine. Any info on would be appreciated.

 

[WillyBWright]

Re: Compression Release Valve 1957 35 hp

I always took off the arm between the starter and rocker arm. I found it easier to start that way. It seemed to draw fuel better and start on fewer pulls. I doubt it's leaking. They aren't open all that much like the valve on a 4-stroke. They tend to carbon-up and seal quite well. Unless a chunk of carbon breaks free and keeps it open a bit. But I haven't run into that.

 

[R. Bushie]

Re: Compression Release Valve 1957 35 hp

As a follow up I have removed the head ( should have done this before). #2 cyl Compression release valve does appear to not be seated. On a measurement, the stem is a few thou shorter than #1. The cylinder walls look good, but the head gasket is showing signs of an improper seating, in that that the copper ring in most of it's surfaces is not discoloured but there is some sign of discolouration in spots. Can I resurface the Compression valve mating surface to assure a good mating? As a follow up is there a head that will replace this one that does not incorporate the Compression release sys?

 

[Paul Moir]

Re: Compression Release Valve 1957 35 hp

Can't help with the resurfacing question, but the later 33hp heads are the same as the 35s without the compression relief valve hole drilled.

 

[BoatBuoy]

Re: Compression Release Valve 1957 35 hp

Paul,<br /> I was under the impression that the '57 Javelin had the compression release, but the Seahorse did not. Did they both have the decompressors?

 

[R.Johnson]

Re: Compression Release Valve 1957 35 hp

You could lap the valve back in using automotive valve lapping compound. That should cure your leakage problem if you have one. I believe your engine is a 58, or newer, and would also have the thermostat in the head. I would not worry about changing the head.

 

[Paul Moir]

Re: Compression Release Valve 1957 35 hp

BoatBuoy, I was under the impression they did but I could certainly be wrong. <br />R.Johnson has a good point, if this is a '58 'Deluxe' (Super-Seahorse) or later 35hp with the thermostat in the head, the 33hp head is different. It matches the '57-'58 (Regular Seahorse) without the thermostat. It has bosses, etc, for the pressure releif system but none of it has been machined.

 

[R. Bushie]

Re: Compression Release Valve 1957 35 hp

The 35 hp in question is a 1957 Ser #25936-50134 and does not have a thermostat. <br /><br />Paul when you mention that a 33 would fit, is there a certain year...from my list of 33's, they were made from 1965 to 70? I only have a list for the Johnsons, so not sure about Evinrude. <br /><br />Even if I can certify the "valves" as no leak I just would like to get rid of them and simplify the system as I have no intention to utilize them.

 

[alcan]

Re: Compression Release Valve 1957 35 hp

Hi R Bushie<br /> You will be far better off following R Johnsons advice on this one. All that is really needed is to wire brush the valves and seats. Relap them if you feel it is necessary. As stated earlier there aren't many problems with these things. Then just simply disconnect the linkage. The main problem with this set-up stemed from the follower at the recoil starter wearing and jambing up the works. Mostly the starter. It is true, that these motors W/O the releese will tend to strain your milk when manual starting. The good news is it only takes a good pull maybe two. I wouldn't go to the bother of finding a new head, nothing wrong with the one you have.

 

[Paul Moir]

Re: Compression Release Valve 1957 35 hp

I agree completely with alcan - repairing the head you have should be a whole lot simpler than finding a good replacement. In fact I've got half an eye open for a setup for my 33hp even though it didn't come with one (33hp were economy models), and I don't plan to use the pull-start much. It doesn't appear to affect reliability significantly.<br />That said, to answer your question any 33hp head ('65-70) should fit fine.<br />EDIT: I missed that your posts above seem to indicate that they're is nothing actually wrong with the head. By all means, reuse it.

 

[Chinewalker]

Re: Compression Release Valve 1957 35 hp

A few thoughts....<br /><br />All of the 35hp Johnrudes from '57 to '59 had compression releases when they came from the factory.<br /><br />All of the 35hp Johnrudes from '57 to '59 had thermostats when they came from the factory. <br /><br />Lots of these 35s blew out head gaskets, particularly if the head was installed without the aid of a torque wrench. I don't recall the torque value off the top of my head, but I think it was in the neighborhood of 200 in.lbs. <br /><br />I don't think I have ever had a valve leak. If it was, enough to affect compression, you'd likely have an oil trail out of the back of the valve down the head, and you'd hear a squeak of air coming out as the motor was being pulled over.<br /><br />- Scott

 

[BoatBuoy]

Re: Compression Release Valve 1957 35 hp

Chine, Thanks for clarifying the years.

 

[Paul Moir]

Re: Compression Release Valve 1957 35 hp

I hate to disagree, but none of the '57 and only some of the '58 engines had thermostats. If you look in the parts guides, you'll see that there's a different impeller for the '57-58 35hp engines (379767) than there is for the '58-59 (w/Thermostat 379768, as it says in the OMC water pump guide). If you don't belive the guide, here's some quick ebay pics:<br /><br />'58 Head with thermostat on tower & compression relief <br /><br /> '57 Lark - although this isn't a great shot, you'll notice no thermostat tower. Clearly visible is the compression relief

 

[BoatBuoy]

Re: Compression Release Valve 1957 35 hp

Paul,<br /> The '58 head in the pic with the tower is exactly like the head on the '57 Javelin I used to have. Although not new in '62, it didn't look like it had ever been tampered with. At the time, I asked the Johnny dealer where I bought it, the difference between the Seahorse and Javelin. He told me the color, cowl, thermostat and decompressors. With that I exhaust my knowledge and defer to you and others with more vast experience.

 

[Paul Moir]

Re: Compression Release Valve 1957 35 hp

Huh. Ok I'm definitely missing something here then. I'm also finding pics of '58 engines missing the thermostat tower - just not the Super Seahorses/Larks. These are certainly not 30hps either since they have the 1 part head. I rather doubt you could retrofit the thermostat since it relys on the recirculating (two water tube) system - so that would mean a differnt mid-section.

 

[Chinewalker]

Re: Compression Release Valve 1957 35 hp

Thanks Paul,<br /> I stand corrected. As punishment for my oversight, I submit myself to attempt to start a 1937 Waterwhich 3/4 hp, or forty pulls of the rip cord, whichever comes first....<br /> It is indeed the Super Quiet models that had the t-stat, not the standard issue models of the 35s...<br />- Scott

 

[Paul Moir]

Re: Compression Release Valve 1957 35 hp

LOL - If I had known the consequences were so dire, I would have kept my mouth shut! Better than 40 pulls on a 35hp without compression relief though. Or three for that matter - the 28hp is bad enough.

 

[R. Bushie]

Re: Compression Release Valve 1957 35 hp

Thanks for the great discussion and the great info. I have to correct myself, my motor is a 1958 35 hp according to my model #25936. I was told it was a 57. It does not have a thermostat. After Chinewalker's comment about not properly torquing the head I checked the head and it was warped (have honed it true), also when I removed the head I did note that the bolts did not seem to have equal tension (several just snug may... have been my initial compression problem).<br /><br />My further question deals with the rings,the initial compression check showed an imbalance, can I check the rings with a feeler gauge for "ring to wall" clearance to insure they are within tolerance? Would this tell me if the cylinder and rings are in good shape since the head is already off, the warpage and compression release sys have been repaired? I'm new to this and need advise.

 

[Paul Moir]

Re: Compression Release Valve 1957 35 hp

There's not much you can tell by looking at the top of the pistons. All you really can see is the condition of the bore, and from that make some assumptions about the condition of the pistons and rings.<br />Scratches along the direction of the piston are bad - the more and deeper they are, the worse. You can get an idea for bore wear by feeling for a ridge near the top of the piston's travel or more accurately by measuring the bore. You will not be able to gauge ring wear (except to assume it's proportional to the bore wear) without removing them and measuring their end-gaps. <br />My '65 33hp surprised me. It had apparantly good compression (100 - 105 psi by my guage) but when I disassembled the engine I found the bores & pistons badly worn from use rather than abuse, and the rings were nearly completely worn out. The end-gaps could be measured with a ruler rather than a feeler guage. There were no gouges in the bore wall and little evidence of overheating on the pistons. It just goes to show that a _very_ thoroughly used 'Big Twin' will still produce good compression.<br />It seems to me that the most common cause of bad compression on these engines besides abuse like overheating or lack of oil, is simply caused by carbon or coke sticking the rings in their lands. Since they no longer press against the cylinder walls, compression is lost. The simple solution to that is to decarb the engine regularly. Occasionally this will cause a great gain in compression as a ring frees.<br />I have yet to see a 'Big Twin' head that wasn't a little warped (few thousandths), so I think that's par for the course. Go over the cooling system - particulairly the water pump - as that's a frequent cause of blown head gaskets. Like Chinewalker said, they're not exactly unheard of anyway. Especially with warped heads and poorly torqued bolts.