what should I do.....

[dave1]

You guys always have great advice. 1960 johnson outboard 40hp ran compression test. 105 on bottom cylinder 70 on top. Motor runs good at high speed not so good at idle. replaced points condenser wires spark plugs and rebuild carb.Thought Id be happy with the way it ran but its not perfect. Would the compression relief valve on that cylinder may be causing that problem. I don't know much about them. Should I pull the head and chance breaking off a bolt ahhhhh.It got hot about ten years ago but not hot enough that the paint is blistering off. shut it down pretty quickly. What would you do or just leave it alone????? Thanks

 

[bktheking]

Re: what should I do.....

I'd pull the head for starters, if you can soak the bolts for a day or so with PB Blaster you shouldn't have an issue. It sounds like you may have a bad head gasket, check the head for warpage, place it on a pane of glass to check.

 

[samo_ott]

Re: what should I do.....

If in doubt I use a propane torch on ever bolt where it goes into the block and it works well. Then when out, wire wheel all the bolts and they will go back in nicely.

 

[kenmyfam]

Re: what should I do.....

And a decarb would only do good.

 

[dave1]

Re: what should I do.....

I guess I'll pull the head. Anyone think those compression relief val;ves are a problem????

 

[bktheking]

Re: what should I do.....

I guess I'll pull the head. Anyone think those compression relief val;ves are a problem????

If anyone would know F_R would, I think he helped develop these motors

 

[dave1]

Re: what should I do.....

my 62 40hp evinrude doesn't have them. Im thinking they are problematic?

 

[bktheking]

Re: what should I do.....

my 62 40hp evinrude doesn't have them. Im thinking they are problematic?

Ok so here is an interesting fact, the release mechanism is built into the pull starter, is this thing electric start and did you test compression with electric instead of manual?

 

[samo_ott]

Re: what should I do.....

I've never heard of them leaking. But it's always possible. I have them on most of my 35's.

 

[dave1]

Re: what should I do.....

cranked it over with the electric start

 

[bktheking]

Re: what should I do.....

cranked it over with the electric start

I'd still lean on F_R with this one, I like Samo have never heard of one causing an issue.

 

[itsaboattime]

Re: what should I do.....

Dave.........before you pull the head, pull the plugs and squirt a little bit of oil into the cylinders. Then repeat your compression test. If your compression evens out then you can bet that your rings are the culprit. If compression doesn't change check for oil residue around the head gasket and your relief valves. If the gasket or the valves are leaking they will show the residue.

 

[dave1]

Re: what should I do.....

yes there is oil around the relief valves running down the head. what kind of oil should I squirt in the cylinders???

 

[itsaboattime]

Re: what should I do.....

I generally use 10W30. A little goes a lonnnng way.

If you already have oil around those valves, then I'd say they are the problem. I'm not sure how to seal them though.

That sounds like a question for Tashasdaddy, F.R. or Silvertip.

Sorry Dude........out of my area of knowledge.

 

[1946Zephyr]

Re: what should I do.....

Don't pull the head just yet!!

Those compression release valves can be an issue, but only if someone has messed with them. Loosen the locking nut on them, then back the stem out. Hand turn the stem in and set the valves at .010 and lock down the nut. Once you do that, then check your compression again. Proper settings can be best obtained, if the linkanges are not sloppy

I picked up an old motor that had one of these set way off and my readings were low on one cylinder too. Once I adjusted them, then everything was fine.

One clarification for dave1: Those compression reliefs were on the 35hp: '57 - '59 and 40hp '60 - '61. The '62 40hp was a redesigned powerhead without the compression relief valves and had a 2 ring piston set. The motors with the compression relief valves, had the 3 ring pistons and were pretty hard to hand start without them.

 

[samo_ott]

Re: what should I do.....

I always heard the compression valves were to be set at 0.020"?

 

[1946Zephyr]

Re: what should I do.....

yea, .020 should be about right. Just as long as there is a gap, you'll be good. These things are just like a valve in a car, but smaller. My old Datsun B-210 had the same stem and lock nut set up as these old big twins do

 

[samo_ott]

Re: what should I do.....

Hey. I used to have a B210 also! But I never adjusted the valves. I did however adjust the valves on my old VW camper vans a number of times

 

[dave1]

Re: what should I do.....

I checked and there is clearance there when not pulling the rope. hopefully someone will have some more insight on replacing these!!!:redface:

 

[dave1]

Re: what should I do.....

update...pulled cylinder head. found scoring at the bottom of my problem cylinder. scoring pretty deep toward the bottom of the cylinder. the top and sides are fine. what would cause this??