Rhojo's '88 Johnson 70's J707TLCCA, updated... reed fix

[Rhojo]

Right on!  At this point I gotta believe the problem has something to do with the reeds, although reed problems aren't the most common problem in the outboard world.  Just can't think of another reason for THAT much fuel to be spitting back out of the carb.  

Either way, if a compression test does not show and issue you are going to have to pull the reed cages and have a look.

 Time to break out the tools.   :twisted:

I looked at the powerhead schematic and it looks good to try to do this without pulling the powerhead.

 Assuming Farley's right, this makes the job quite a bit easier.  Do you have a service manual?...or at least a good parts schematic to follow?

Thanks for the input G!

I do have a manual to consult.

OK, I'm going to pull the carbs and intake manifold, that's going to mean a new intake gasket and probably carb gaskets as well?    Then I'll get to see the reed block. I have it on good authority (Thanks Lewis! ) that if I need to replace reeds that I should go with the dual stage reeds from Boyesen http://www.boyesen.com/OUTBOARD. The difference is night and day according to Lew. Anyone else had expierence with these? Of course, if I do this to one of the twins I can't leave the other out in the cold so I will consider doing it to both, one at a time but collecting all the necessary parts at once.

 8)

[Georgie]

that's going to mean a new intake gasket and probably carb gaskets as well?  

Yup.  Pretty minor cost, just make sure you're careful removing the old gasket and preparing the surfaces for reassembly.  Use sealant only when instructed by OMC.  Fingers crossed you'll find an obvious issue in the middle of your reed block.

RE: Boyesen, I have a set and have researched them like crazy but I haven't installed them yet.  I've read many positive reviews, and it sounds like Lew has had positive experience, but then my local OMC mechanic who has owned the best OMC shop in town for 30+ years and used to race these engines all the time says not to use 'em, so to each his own I guess.    Since it appears you can replace yours without removing the entire powerhead, and since failed boyesen reeds don't chew up your pistons/rings like the steel ones can, I'd say go for it.  If you're unhappy or they fail, you can just pull them back off and reinstall the steel ones.  Make SURE you follow all OMC and boyesen installation instructions precisely.  

[fitz73222]

I've run Boyesen reeds on hopped up engines before and really didn't see any benefit besides the fact the engine can swallow them and live through it. The fact is that they will wear out; I've seen it. They are basically fiberglass and you will be replacing them again at some point. Factory reads are cheap and available. One other thing Jon; when you did the compression test, did you turn the engine over no more than 5 compression strokes with the throttle butteries held wide open or just crank it until the compression gage stopped moving?

[Rhojo]

I've run Boyesen reeds on hopped up engines before and really didn't see any benefit besides the fact the engine can swallow them and live through it. The fact is that they will wear out; I've seen it. They are basically fiberglass and you will be replacing them again at some point. Factory reads are cheap and available. One other thing Jon; when you did the compression test, did you turn the engine over no more than 5 compression strokes with the throttle butteries held wide open or just crank it until the compression gage stopped moving?

Not more than 5 turns , that's what I did. I did not do anything with the throttle butteries. What is that?  

[fitz73222]

Compression is all about air in and air out. By opening the throttle butterflies wide open, you allow the engine to suck in more air and hence it can actually raise the compression but for this excersize as long as it's even, we're OK

[Rhojo]

Compression is all about air in and air out. By opening the throttle butterflies wide open, you allow the engine to suck in more air and hence it can actually raise the compression but for this excersize as long as it's even, we're OK

Makes sense.  :)

Thanks Farley!

OK, I'll post my findings when I get the carbs and intake off!

[wingtime]

Another source for reeds is Chris Carson marine.  http://www.chriscarsonmarine.com/reed-valves.htm

[GoneFission]

I've read several studies on different reed setups and most find very little difference in performance of aftermarket reeds compared to factory original.  Rubber-coated reeds seem to idle a little better, and (as has already been said) fiberglass reeds will not destroy an engine if they break.  But it's rare that factory reeds break unless something else causes it, and both fiberglass and rubber-coated reeds do wear...   Think about the scientific method here of only changing one thing at a time - if you change several things and the problem is fixed - you don't really know which thing fixed it...

[slvrlng]

OEM reeds, pretty cheap.

http://www.marineengine.com/newparts/pa ... OMC0313420

[Rhojo]

Carbs off and peeking inside...I see a broken reed...


Having trouble getting the pics from the album to show in the post, here is a link to the album...
http://www.classicaquasport.com/gallery/showgallery.php?cat=684

My question now is where is the rest of that reed and what do I do about it?

[dburr]

When you get the reed block out Jon you may find that the reed is torn/cracked and all the pieces are still there..  I am going to cross the chicken bones and hope for that. GOOD find .

If stuff is missing, a bright light and a small mirror is a place to star.t.


 Farley, what say you?

[fitz73222]

Carbs off and peeking inside...I see a broken reed...


Having trouble getting the pics from the album to show in the post, here is a link to the album...
http://www.classicaquasport.com/gallery/showgallery.php?cat=684

My question now is where is the rest of that reed and what do I do about it?

It swallowed it. Now I have seen engines swallow a reed and never touch a thing on the inside, however yours is a big chunk. We did the compression test to verify there wasn't major damage assuming it ate the reed, but a cylinder leakdown test is the best way to determine if the rings are actually sealing and able to hold pressure.  But to truly verify no damage has occured, it's time to pull the cylinder head and visually inspect the cylinders and ports for damage. It is very rare for this to happen on a "fishing" engine and is more typical on 6500+ rpm HO engines, hence the composite reeds necessity. The head is easy to pull. disconnect the temp switch wire and just remove the outer perimeter larger bolts. I'm pretty sure there are no water cover bolts and plate since you have the lost foam cast cylinder head assuming a 1985 or newer engine. Take the bolts out and tap the cylinder head with a block of wood and a hammer to break the gasket seal; it may take several good raps to break it loose then take a look.

[slvrlng]

A little help. Hopefully the missing piece is sitting right on top of one of the ports.

[Rhojo]

Oh dear, well I didn't see the piece or any fragments at teardown so let me go back and look a little closer  

[fitz73222]

Interesting, look at the stress cracking on the reed cage face in the area where the reed contacts the cage. This may be the reason why the reed broke. The cage may have worn to the point that the reed petal started landing against the cage on one side of the petal and eventually split it in half. Look at the casting quality of that cage compared to the other two. Looks like a metallurgy issue with that cage. Fascinating...