pulse/vacuum hose replacement johnson/evinrude 18hp

Daveparm

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I have a 1965 johnson 18hp in which had a hardened (to the point of it cracking off with slight pressure) hose/tube that runs from the pulse fitting (oppisite the fuel pump) to the intake manifold to the left of the carb. The nipple on the fuel pump side is very small (1/16 inch or smaller) while the other end is quite a bit bigger (1/8 inch or larger). Is the oem hose pre stectched for the different diameters? If not, can I get away with over the counter general hose replacement? I also have a 1972 evinrude 18 which appears in similar condition.

There is also a hose from the lower portion of the crankcase to the upper ( I suppose to help lubricate the upper bearing) that also appears hard and probably brittle.
 

Crosbyman

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the side oiler hose is sometimes replaced with clear fuel line hose ...to see the oil flow up

1/16... ? seems small but ...
​the difference between 1/16 and 1/8 in not much ... get what fits and clamp the hose at each end with tye wraps
 

Joe Reeves

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The line for the main bearings..... you can use speedometer hose.

The line with two different diameters... give us a part number. I or some other member may have one left in stock.
 

racerone

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Does the 1965 model 18 hp have the original powerhead installed ??
 

F_R

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Does the 1965 model 18 hp have the original powerhead installed ??


Doesn't sound like it. That describes the 1973-ish crankcase drain hose leading to the upper bypass cover, doesn't it? Yep, it is a special hose with two I.D.s
 

F_R

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The crankcase drain hose is part number 0317120 hose, manifold to cover. They are mighty proud of it ($).
 

Joe Reeves

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317120 Hose..... If you have a problem finding one, PM me.
 
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Daveparm

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Sorry I couldn't get back sooner. I ran home during lunch and checked the two motors. Pretty sure the 65 is the original powerhead, but have no idea on the history of it. The paint looks to match a little to perfectly. The 65 does have a metal tube that connects upper and lower bearings, the 72 is plastic. They both have the tube that runs from the pulse area to the intake, but the 65 has the hose connected to the bottom cylinder and the 72 has it on the top. Obviously this means that the fuel pump is on the top on the 65 and bottom on the 72. $15 for a new one sounds fair enough. On the 65 I show a hose/tube part number 308506, but that could very well be the metal one (hard to make out from the diagram exactly where it goes). The diagram I am looking at doesn't seem show the other hose on the 65, which is why I guess you are thinking a different vintage. Again If I was a betting man I would say it's original. Joe, Do you have 2 new ones? (both motors)
Thanks. I will also try to post a few photos.
 

Daveparm

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BTW, the original sizes I gave for the hose end sizes are approximate (1/8, 1/16) With any reasonable thickness tube it would be impossible to get tubing that would fit the small nipple around the large one without trying to reform it with the use of heat.
 

Daveparm

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If it helps, here are the hoses I am referring to. One I am calling an oil tube, the other is the crankcase drain as per FR's post.
 

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Daveparm

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I'll use clear fuel line for the 1972 oil tube as suggested above.
 

F_R

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I don't know what the heck you have (you say 1965). I've never seen one with the nipple installed that way in the bypass cover. The original 1965 didn't have a recirculating crankcase drain. It just dumped the drainage overboard---internally so you can't see it. I think the recirculating drain started in 1968, and it wasn't even a recirculating drain. It dumped the drainage into the exhaust stream, but not via a fitting such as you show.

I believe you have a replacement powerhead on that motor. I say that because of the funky drain, and the fact that the serial number plug is missing.

Your 1972 looks normal.
 

Joe Reeves

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I only have the one special 317120 hose. I'm just going by the part number as per F_R's reply. Whether it's what you need or not, I don't know.

This one is roughly 11-3/4" long.... the hole sizes are (also roughly) 1/8 & 1/16... Seems identical to your description. PM me.
 
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F_R

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Wanna know my wild guess? On the 1968 models, the drain hose attached to a special fitting that replaced the lower right hand bolt holding the lower bypass cover on. That bolt hole went clear through to the exhaust area. So, the drainage went into the exhaust stream. My guess is that somebody figured that cannot be right, and drilled & tapped the cover for a fitting. I suppose it will run that way, but the lower cylinder will be chronically rich due to that drainage being dumped in there.

To make that guess viable, you have a '68 powerhead.

Believe it or don't believe it. I'm not even sure I do.
 

Daveparm

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All very interesting. O.K., I'm convinced. I have a powerhead from a later model. Can someone explain the drain process and what the hose is intended for? What should I do to make the 65 motor proper. Should I cap the pulse nipple and run the hose to a new location. Should I try to locate the lower right fitting for the bolt hole? Or.. should I switch the pulse access covers top to bottom (if that is even possible)and run the tubing exactly like my 72? Am I correct to assume if I tried to run it with the line open it would be a huge vacuum leak to the crankcase? Thanks all!
 

F_R

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First some history: Those were some of the best motors ever made---up until 1968 (maybe 1967?). But they did that at the expense of dumping raw fuel into the lake. So, due to environmentalist's pressure, OMC changed the drain valves, eliminating some of the drainage, and what was left was dumped into the exhaust stream where it hopefully was burned or evaporated (not). The motors still ran fairly well, but those in the know could tell the difference. And the improvement in water contamination really didn't change much. But the BS satisfied the government.

Forward to 1972-ish, the system was changed again, and the drain valves produced even less excess fuel to get rid of, and it was routed to the upper cylinder bypass cover where it was injected directly into the cylinder for burning. That is the system your other motor has. Again, for those in the know, we felt they ran really crappy, compared to the old ones. But if you are happy, so are we. BTW, the drainage came from the lower part of the crankcase (gravity), so it is routed to the upper cylinder to compensate and even things out.

OK, if you want to route the drainage by 1968 design, first you need to remove that lower bolt and see if you can blow through the hole. If you can, good. Then you need to obtain the fitting and gasket washer. Then simply attach the drain hose to it and you are ready to go. It is NOT one of those crazy hoses.
 

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Daveparm

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It never fails to amaze me, the knowledge on this forum! First off, I checked for the 68 special fitting and it looks like it will be pretty impossible to find. The washer/gasket is available though. I am currently at work, so I haven't checked to see if that hole is clear yet. Based on your explanation, I could plug the existing cylinder fitting (not needed), correct? If so where to run the drain hose-- out the lower cowl? If so, wouldn't this still create a vacuum leak in the lower crankcase?
Did OMC change what was behind the covers, or just the covers themselves? Do you know the year they switched from steel tubing compression fitting oil tube to rubber hose? That might help me determine if this is an original (but modified) powerhead, or a 68 replacement? Thanks.
 

F_R

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I gather you are thinking of doing it the easy and dirty way, right? Sure, you can plug the existing fitting in the lower bypass cover and run the hose overboard. That wouldn't be any worse than the original setup of the early '60s. Or you could be more decent and recover the drainage in some sort of a container.

As for a vacuum leak, no it will not. There are one-way check valves in the reed plate to prevent air going into the crankcase. And the little bit blowing out is not significant.
 

F_R

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Well I still don't know exactly what the heck you have. The bottom to top oil line was changed from copper compression fittings to a rubber hose in mid-1962.

As for the drain hose, I would have to get inside the reed plate/intake manifold to be sure. But now I suspect you have a 1962 or older with a drain system that somebody modified (1962 did not have an external drain system. It was all internal, out of sight)
 
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