15HP Johnson runs great on muffs / bogs at the lake

[dejamat]

I just read somewhere that if you lose the prime on the bulb this could happen, the fix was to make sure the bulb is facing upwards so the fuel keeps the check valve it the bulb moist and hold the prime. Try it, for sure it won't hurt. Good luck

 

[Charger25]

This is Betty. Yep I've named 'em all

 

[Succotash]

Well I've got bad news.

I got my fuel pump rebuild kit from iboats, and rebuilt it in accordance with leroysramblings website. I checked it by blowing through the inlet port (which allowed air to flow through) and then blowing into the outlet (which did not allow any air to pass). This check convinced me that I had rebuilt my pump adequately.

I confidently brought the boat to the lake, and launched it into the water. I primed the prime bulb until hard and gave the rope a pull, to my surprise it started right away. I then checked the pee hole to ensure the impeller was pumping, which it was. I then began to troll around at around 20% throttle, and did this for a few minutes. Everything was starting to seem as if I resolved my problem.

I placed it into neutral to let the engine idle a bit, and after a few seconds it suddenly bogged down. As it was bogging, I gave it a little more throttle (to try and keep it running) which only bogged it down faster.

I made several attempts to restart the engine, with no luck. No matter what I tried, it just wouldn't start. I checked my prime bulb, which was very hard. So I am convinced that my newly rebuilt pump is sufficiently pumping.

I loaded up the boat and drove it back to the house, where I quickly got out my large bucket and placed it under the engine. After filling it with water, I went ahead and tried to start the engine. Amazingly it started right away, and idled like normal. I revved it a few times, killed it, and restarted many successful times. I placed it into forward and reverse gears and let it troll for a few minutes with no issues.

I am totally stumped here. Maybe it's overheating under load? Maybe the powerpack loses spark when it gets hot? I should have checked for spark out at the lake when it was refusing to start.

On a lighter note, I repainted the whole outboard in white, and put on a new decal set.

 

[harleydoc]

Sounds like a restriction in the fuel flow, maybe check all the lines ,bulb ( one of the valves could closing ) and the pick up in the tank. If it has a screen it could be partially clogged. Like whats been posted it wouldn't hurt to the diaphragm and spring in the fuel pump. It also has a screen as well.
If it does not have a thermostat that would explain the excessive water coming out of the exhaust relief. IMO nothing to worry about unless you run it in the winter. Some say ya gotta have a t-stat some don't. I only had them in the larger outboards I've had cause I did run them in the cooler months. Made them easier to start after warming up.

On a side note, nice Wrangler ! Got an older Renegade myself.

I went ahead and ordered a fuel pump rebuild kit today from iboats, hopefully it will take care of the problem. I'm also going to inspect the pick up within the tank.

As for the thermostat, I just put a new one in it. I'm guessing the water coming from the upper exhaust ports is normal, I noticed the same thing happening on several youtube videos.

Here's how the jeep looks now, lol. It's been through quite a bit...

I see that yota is help you limp home... JK them some bad looking rigs.

 

[john300exc]

I am the original owner of a 1977 Johnson 15 hp, short shaft, manual start.
The motor has been used very little, spent most of it's life covered in a shop.
I bought a Tracker Grizzly 14' boat several years ago and have been frustrated every time I tried the motor on this boat. As you describe it seemed to run fine on muffs but when on the water it bogged with the prop loaded. I took the carb apart and cleaned green sediment from the bowl. I removed the main jet and sprayed it with carb cleaned, it did not appear obstructed. Reassembled and back in the water, same problem!!
I thought about it one night and decided to take the carb apart again for another look at the jet. I found my cleaning kit for a paint spray gun which has tiny brushes of different sizes and several small metal picks. With carb cleaner and brushes I attacked the jet and after several passes with progressively larger brushed it was apparent to me that the jet orifice had been partially obstructed. The hole in the jet was now noticeable larger.
Back in the water (I live on an 18 acre lake) armed with a GPS and PET-2100DX tach, the motor was a completely different beast.
Before it would only manage 8-9 mph & 4900 rpms and would not get the boat on plane. I knew it was lean because I could open the choke quickly and it would gain rpms. Now with the main jet cleaned it will pop the hull up on plane and I was able to get 18.3 mph at 6200 rpms. The data plate on the motor says operating RPM is 5,500 to 6,000 rpm. This is probably the best I can get from this boat/motor combination. This 14' boat weights 437 lbs. and I am 235 lbs. and there is a large battery for the trolling motor. This boat is also fairly wide with a 72" beam according to the Tracker website.
I also use non-ethanol fuel but have probably had some ethanol through the motor. This ethanol fuel is a disaster for motors that are run infrequently.
Take a good look at your main jet and make sure it is completely open and not partially obstructed like mine.
Good luck.
John

 

[Succotash]

I appreciate the responses everyone,

I took the boat out again today to check for loss of spark. To my surprise, the boat ran flawlessly! This is crazy, it went from being near impossible to run on the lake, to running 19mph (GPS) with a partner, 4 rod and reels, tackle, battery, trolling motor, and misc. other crap.

I cruised around the lake for probably 45 minutes. The engine idled well and had nice, crisp throttle response. The only deficiency was while attempting a full throttle launch from a dead stop. When I try, she bogs down. However, if I gradually accelerate for a few seconds, then punch it, she takes off pretty quickly. So as long as i dont "slam" the throttle from a stop, it accelerates just fine. (I'm sure this is just a low speed needle issue.)

Other than the full throttle digs, the engine ran great. I figure 19mph is pretty good for a 15hp on a 1436 with a deck and two people. I'll GPS it by myself in a few days when I get my trim adjusted properly for boating alone.

 

[Charger25]

Glad ya got her going ! =D> Thats exactly how fast mine runs 19 mph and the boat loaded about the same.