Video - Is this '57 Johnson running okay?

[adt2]

I decided to post a new thread on my motor woes, since the water pump issue has been resolved. My current issue is that I don't think the motor is "revving" like it should. According to the designer, a 25HP motor is more than enough motor for my Macomber 15 skiff.



I figure if 25HP is enough, then 35HP ought to be able to plane her out. So far, I've been wrong. We took her out for the first time last weekend, and due to a host of motor issues we weren't ever able to get her to plane. I'd guess top speed at WOT was about 10-12MPH. At WOT the motor sounds like it's ventilating/cavitating, but I don't know for sure. Here's a short video clip of the motor running at idle and at WOT (does not make the vent/cav sound in the barrel):

The designer did not specify - and, incredibly, I didn't think to verify - whether a long- or short-shaft motor was necessary. My motor is a short-shaft; the transom is 18" high. The anti-ventilation plate above the prop is just a hair (~1/4") higher than the bottom of the boat. There's a 1"-thick outer keel mounted (obviously) outside the bottom, making the plate ~1-1/4" above clean water. Reckon I ought to cut the transom notch a little deeper, or should I exhaust all other possibilities first?

Thoughts?

 

[HighTrim]

Re: Video - Is this '57 Johnson running okay?

In the video, were you in gear or in neutral?

 

[adt2]

Re: Video - Is this '57 Johnson running okay?

It was in neutral, but shifting into gear doesn't result in a noticeable change. (Don't have a video with it in gear.)

 

[Chinewalker]

Re: Video - Is this '57 Johnson running okay?

For neutral running, the motor sounded good and didn't sound to me like it was only firing on one cylinder. But, sometimes it can be tricky to tell, especially in a video.

I can't tell from the video if you've got proper carb linkage movement. With the shifter in gear, does turning the thottle handle give you full travel on the magneto and carb linkages? The "hammer" attached to the carb butterfly arm should rotate forward and contact the stop on the carb body. If it doesn't go all the way, then you've got linkage issues. It should not go all the way in neutral (if all the shift interlock features are intact.)

 

[geoffwga1]

Re: Video - Is this '57 Johnson running okay?

No!! It's definitely not running OK.WOT in a barrel and it should nearly jump out of it.Have you checked you are running on both cylinders?Have you stripped and cleaned the carburettor (thoroughly)? have you checked the coils for cracks etc ,and the points and condensers.Finally,is the throttle butterfly valve opening correctly.Have you good compression on both cylinders.
Geoffwga1

 

[adt2]

Re: Video - Is this '57 Johnson running okay?

...didn't sound to me like it was only firing on one cylinder...

With the motor idling along shortly after the video was taken, I pulled each spark plug wire off in turn. Each time, the RPMs fell off significantly until the wire was re-attached. My understanding is this means both cylinders are firing.

I can't tell from the video if you've got proper carb linkage movement. With the shifter in gear, does turning the thottle handle give you full travel on the magneto and carb linkages? The "hammer" attached to the carb butterfly arm should rotate forward and contact the stop on the carb body. If it doesn't go all the way, then you've got linkage issues. It should not go all the way in neutral (if all the shift interlock features are intact.)

I'm really not sure; I'll have to identify those parts on the exploded view and inspect them for proper operation. However, I will say that one of my "suspected issues" from the get-go has been that I don't think the twist-grip throttle is getting "full travel." It only turns from about 12 o'clock to about 3 o'clock (as can be seen in the video). That would kind of jive with what you're saying - maybe I've got linkage issues.

 

[adt2]

Re: Video - Is this '57 Johnson running okay?

No!! It's definitely not running OK.WOT in a barrel and it should nearly jump out of it.Have you checked you are running on both cylinders?Have you stripped and cleaned the carburettor (thoroughly)? have you checked the coils for cracks etc ,and the points and condensers.Finally,is the throttle butterfly valve opening correctly.Have you good compression on both cylinders.
Geoffwga1

It doesn't "nearly jump out" of the barrel in either neutral or forward gear. As I said, shifting into forward makes almost no difference at all as far as engine revs (perceived RPMs - I don't have a tach hooked up to it). Yes, I'm running on both cylinders. No, I haven't done any carb work other than adjusting the high- and low-speed needle valves. No, I have not checked coils, points, or condensers; this is my first foray into anything more mechanical than Legos, so I'm taking it slow. I believe the butterfly valve is opening correctly; several guys who know more about this stuff than me have peered down into the carb, twisted the throttle, and said, "Yeah, it's working." I haven't checked compression yet.

 

[HighTrim]

Re: Video - Is this '57 Johnson running okay?

Ok, I was assuming it was in neutral due to the limited travel of the tiller grip.

As Chinewalker stated, I do not believe you are getting full travel of the magneto and carb linkage, IF putting it in gear does not change the amount of movement compared to your video. The throttle will advance quite a bit more in gear than in neutral.

Make sure the neutral lock is not still engaged when you shift, follow the linkages and you will see how it works. Shifting from neutral to forward and back should determine how far the magneto will advance. I could go downstairs and take a pic of a similar motor if need be.

 

[adt2]

Re: Video - Is this '57 Johnson running okay?

If you've got a similar motor and could post a picture, that would be outstanding. I looked over the exploded views at lunch, and I was having a hard time deciphering how all the linkages work together - particularly since my parts catalog doesn't show a steering arm assembly at all. My catalog (P/N 377024) lists a couple of items on the Lower Unit Group page that I think are part of the problem: #6 (listed simply as "Gear") and #8 ("pinion"). The pinion is what is rotated by twisting the throttle twist-grip; it's at the opposite end of the assembly from the twist-grip. On my unit (and shown in the video above), this thing doesn't turn very far at all from lock-to-lock.

Looks to me like, from the "gear," the motion is transmitted via what the catalog calls a "lever" (#18 on the Powerhead Group page) and from there through a "pivot pin" (#78) and a "rod" (#108).

From there, I can't tell what's supposed to be happening. Maybe the "throttle shaft & arm assembly" (#47 on the Carburetor Group page)?

One last thing; I went ahead and picked up a carb kit when I bought the new water pump impeller (mostly to save myself a trip across town to the supply house later). It's a Johnson 18-7024 kit, Sierra P/N 439075. There appear to be more parts in the kit than are actually on my carb, but I can't find a list of P/Ns included in the kit anywhere online. Every single site selling this thing has exactly the same picture and zero information about included parts. What exactly am I supposed to replace when I rebuild this thing?

 

[Chinewalker]

Re: Video - Is this '57 Johnson running okay?

In the carb diagram, the combination of #47 and #116 are what I referred to above as "the hammer". It rotates with the throttle butterfly shaft. It needs to move almost horizontal at full travel, and it rests against a stop boss cast into the carb body. If it's not getting there, you ain't getting full travel...

 

[adt2]

Re: Video - Is this '57 Johnson running okay?

Okay, I'll give that a look-see when I get home this afternoon.

One more question - how long should it take to re-build the carb if I decide to do it? An hour or two, a day or so? Keep in mind I'm a handy guy (I built the boat the motor is sitting on) but just getting my feet wet in the world of mechanics.

 

[Chinewalker]

Re: Video - Is this '57 Johnson running okay?

I rebuilt a Big Twin carb this morning, before breakfast - but I've rebuilt more than a few. All told, it should take you a couple hours if you're doing it right. That includes pulling and replacing the plug on top, removing and replacing the needle packings, replacing the float needle & seat, and a thorough cleaning of the carb body & bowl.

 

[HighTrim]

Re: Video - Is this '57 Johnson running okay?

You will have alot of leftover parts in the kit, as the kit covers more than one motor.

Your first carb may take a bit, but once you get the hang of it I can do a 50s OMC carb in no time at all.

 

[kfa4303]

Re: Video - Is this '57 Johnson running okay?

HI adt2. Glad you got it running. A carb rebuild isnt' bad at all. In fact, it's part of routine maintenance that should be done every season, along with changing the impeller and lower unit gear oil. It should only take and hour or two on your first outing, but you'll get better and faster at it the more you do them. Here's a link that can walk you through the job. It's for a different model, but all the steps are basically the same. Pay special attention to the welch plugs. You can get a carb rebuild kit right here at iboats for about $25. The motor seems to be pumping water and idling well enough, although you should definitely have more travel/twist in your throttle when in either FWD or REV gear, there is however a mechanical rev limiter which limits the travel of the magneto while you're in Neutral to prevent a "runaway" motor. Follow the throttle linkages starting at the tiller, up through the lower cowl and around to the opposite side of the motor to see if there is anything impeding the movement of the armature plate. Pay special attention to the gear shift lever which acts as a stop for magneto while in neutral. It it supposed to move out of the way when the motor is in gear, but it may not be. I think it's just something simple and mechanical. You can also try manually advancing the throttle by rotating the vertical throttle tower with the idle set screw at its base as if you were using control cables. That way you can eliminate the tiller handle portion from the equation for now and focus on the rev issues.

http://www.outboard-boat-motor-repa...hnson 5.5 HP 1954-1964 Carburetor Tune-UP.htm

 

[adt2]

Re: Video - Is this '57 Johnson running okay?

Thanks for the info. I'll look for the mechanical gremlin you're thinking of. I think I'll put off the carb rebuild until next week; I don't want to try to rush it tonight (we're planning on taking her out for another spin tomorrow morning), but I can start it Sunday or Monday and have plenty of time to finish it before next Saturday for trip #3, I think.

Any thoughts on whether the transom cutout needs to be deeper? Kind of surprised I haven't gotten any opinions on that yet. (Sorry, this is the best picture I have of the transom/motor area right now.)

 

[Chinewalker]

Re: Video - Is this '57 Johnson running okay?

The tilt angle looks a little high, but otherwise the AV plate looks to be about deep enough for you. Might want it level with the keel of the boat to prevent keel turbulence from interfering with the prop.

 

[adt2]

Re: Video - Is this '57 Johnson running okay?

Yeah, we "discovered" (translated: "remembered we'd screwed with it before launching and forgot to put it back") the tilt pin at the bottom of the transom bracket was not in the "down" position for our maiden voyage. That has since been remedied.

My current options for lowering the motor are to deepen the transom cutout (easy, but requires sanding and varnishing afterwards), cutting off the outer keel a few feet forward of the transom (a little harder, has to be done upside-down and will require some paint paint and caulk touch-up), grinding the outer keel down flush with the transom starting a foot or two back (lots of work and may or may not help), or buying a long-shaft motor (or long shaft lower unit). Currently I'm leaning toward just cutting the transom deeper.

 

[boobie]

Re: Video - Is this '57 Johnson running okay?

IMHO it looks pretty good.

 

[nwcove]

Re: Video - Is this '57 Johnson running okay?

the motor sounds good, but as mentioned by others , it seems like the neutral stop may be keeping it from getting to wot.
as far as the motor height goes, its hard to tell from that pic. place a straight edge on the keel and take a pic. it does look about an inch or so high to my eyes tho. shame to cut that purdy transom.....but if needed its the best option.

 

[Chinewalker]

Re: Video - Is this '57 Johnson running okay?

You're very close now. Adding a long shaft would make you much too deep. I would fix the engine issue and go from there. If the prop ventilates, you're too high and you could trim the transom down a little at a time. Trim it, run it, trim it, run it. Once you find the sweet spot THEN finish the top cap.