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pinchvalve (Forum Supporter)
pinchvalve (Forum Supporter) MegaDork
7/26/21 2:32 p.m.

I bought a brand-new fuel line from the can to the motor, maybe they assume that newer engines pull fuel harder with electric pumps?  I am using a larger-ID line for my replacement line. All internal lines have been replaced as well.

The vent on one tank is open, the other has no vent so you have to uncsrew it a bit. If you don't, the fuel pump will collapse the plastic tank. That tells me that the pump is fine for pressure, just not for flow.

java230
java230 UberDork
7/26/21 5:28 p.m.

In reply to pinchvalve (Forum Supporter) :

Ugh. Sounds like pump works if it collapses the tank. Didn't realize you had already replaced the lines... Not sure what else could be going on since pumping the bulb fixes the issue. Carb Float setting? (I am not a carb guy.....) 

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) GRM+ Memberand MegaDork
7/27/21 10:40 a.m.

The mechanical pump on an outboard uses crankcase vacuum to operate a diaphragm.  It will straight up collapse a tank in short order.  If I forget to vent my Merc tank, I get about 1 mile up the lake and it starts running poorly and I look back to see my plastic tank all deformed like a bent soda can.

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) GRM+ Memberand MegaDork
7/27/21 10:48 a.m.
Brett_Murphy said:
pinchvalve (Forum Supporter) said:

The hull is rated for 110hp, so now that i know the hull and interior are in good shape, I may keep my eye out for a more modern 4 stroke outboard.

 

 

The hull was rated for a 110 HP *two stroke* engine back when the boat was built. Old 2 strokes usually weigh less than modern 4 stroke engines of similar horsepower. I looked up a 1972 Johnson 85 HP outboard, and it weighed about 250 pounds. A modern Yamaha 90 HP 4 stroke is getting bragged about for being light, and it weighs 100 pounds more.

That's quite a bit of weight on the aft of the boat.


 

I wanted to swing back to this.

Another tidbit to know is that somewhere around the early 80s, the standard for how HP is measured changed.  In the old days, power was measured at the flywheel.  It is now measured at the prop, meaning a more modern outboard makes more power for a given rating.  The drive and transmission saps about 10-15%, so a newer 100 would likely perform the same as an older 115.

When dad repowered his 1968 boat, the max hp rating was 85 on the tag.  He got a 70 knowing that the 1988 motor he bought was rated differently than when the boat was manufactured.  I tried to convince him to do the 80 because I wanted that extra 3 mph, but alas.

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) GRM+ Memberand MegaDork
7/27/21 10:52 a.m.
java230 said:

In reply to pinchvalve (Forum Supporter) :

Ugh. Sounds like pump works if it collapses the tank. Didn't realize you had already replaced the lines... Not sure what else could be going on since pumping the bulb fixes the issue. Carb Float setting? (I am not a carb guy.....) 

The pump diaphragms sometimes get a pinhole.  Depending on the engine, it will flood or starve.  Some pumps reference directly from the crankcase and they'll suck raw fuel in bypassing the carbs.  Others just go weak.  But, since they are referenced to vacuum, they will always suck the tank, even if they're not properly delivering fuel

java230
java230 UberDork
7/27/21 11:25 a.m.
Curtis73 (Forum Supporter) said:
java230 said:

In reply to pinchvalve (Forum Supporter) :

Ugh. Sounds like pump works if it collapses the tank. Didn't realize you had already replaced the lines... Not sure what else could be going on since pumping the bulb fixes the issue. Carb Float setting? (I am not a carb guy.....) 

The pump diaphragms sometimes get a pinhole.  Depending on the engine, it will flood or starve.  Some pumps reference directly from the crankcase and they'll suck raw fuel in bypassing the carbs.  Others just go weak.  But, since they are referenced to vacuum, they will always suck the tank, even if they're not properly delivering fuel

Good point, I completely forgot about that! 

pinchvalve (Forum Supporter)
pinchvalve (Forum Supporter) MegaDork
7/30/21 2:42 p.m.

So not sure if I included this update, but one other project delayed my fuel line testing. One time out on the water, I could not get the throttle back to neutral, which meant it would not start. Normally, I would take apart the control box and figure it out, but we lost the anchor and the river was taking us towards some rocks (YES! I am new to this and learning!) so I kinda jammed it into place. Turns out that a plastic piece internally was failing and I pushed it over the edge. It worked the rest of that day, so I moved on. 

Last week, we took it to the water and got everyone on board, but I could not get it into reverse. I put it back on the trailer and apologized to the family. I removed the cover and was able to manually shift into FWD or REV and the throttle was still working, so we put it back in the water and tried again. Everyone jumped on board and I went to put my son's life vest on...dammit I forgot the vests. (I AM NEW TO THIS) So back on the trailer. I ordered a laminated boating checklist, learning from pilots and astronauts.

I wasn't sure if I could replace a piece of plastic from the inside of a control unit from a 1977 Johnson, but it arrived in 2 days. Man I love the internet. Hoping to get it wet tomorrow and see if I have fixed anything correctly.

mtn
mtn MegaDork
7/30/21 3:20 p.m.

If you have the storage space, I recommend keeping a set of cheap life jackets in the boat or else in a plastic tub that lives in the boat, and is moved to the car at the ramp. Stops this from happening.

 

Also, forgetting/losing the anchor is how all the boats I use nowadays have 2 anchors on them. Overkill much?

pinchvalve (Forum Supporter)
pinchvalve (Forum Supporter) MegaDork
8/24/21 4:29 p.m.

UPDATE: It runs.

I connected a fuel pressure gauge to verify that I had pressure at the carb. With the on board pump I was seeing 2PSI which is what it wants, with the electric pump I was seeing 6. The additional fuel pressure wasn't helping with the issue.

I decided to remove the carbs and rebuild them one more time. The only thing I noticed was that the seat for the needle valve was raised a bit. I torqued them to spec which lowered them part of a millimeter, which allowed the needle valve to open by the same amount. I also removed all orifices rather than just clean them to ensure that they were seated properly. Not sure what did the trick, but it runs at WOT without the electric pump and never stalls from fuel starvation. I think that I can do some fine-tuning, but am very happy that it runs all day without issue. 

 

 

 

 

 

mtn
mtn MegaDork
8/24/21 4:37 p.m.

I'm still astounded at how nice this came out. Happy you got your Johnson up again. 

pinchvalve (Forum Supporter)
pinchvalve (Forum Supporter) MegaDork
9/7/21 7:14 a.m.

Took the boat to a lake for the first time for Labor Day and had a great day on the water. No issues other than she needs a shot of starting fluid to get going in the morning after sitting for a few days and the quick disconnect leaks on my spare tank. Both are easily solved.

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) GRM+ Memberand MegaDork
9/7/21 11:03 a.m.

Nice work, man.  Truly.

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