1986 Johnson SPL fuel/carbs problems

[zach103]

I have a 1986 Johnson SPL 90hp. I wil get the model and serial number in the morning.. Last year the gas was old and ended up clogging the carbs. I took the carbs off and rebuilt both carbs, I broke part of the fuel pump in the process so ended up replacing the output part of the pump. I started it up today and it was only pushing fuel into one carb, I tried to adjust the red knob to get fuel to both carbs but when I get both lines full of fuel the motor shuts down. I will only start with one carb getting fuel not both. Also i noticed that if i pumped the primer enough fuel would leak out of both carbs. I'm assuming I screwed something up while rebuilding the carbs but can't afford to bring it to someone to repair. Thank you.

 

[emdsapmgr]

Any chance that the fuel lines to that carb are restricted? If not, then the problem is with the carb. You'll have to pull it apart. Look at the float needle and seat-esp pull the seat and make sure it is open. Is the float installed correctly? Normal movement? Also pull all the jets out and visually inspect them (6 per carb) to be sure they are open. Then clean the internal passages in the upper carb body with an aerosol carb cleaner similar to a Gumout product.

 

[zach103]

Both lines from pump to carb are clean and free flowing. One is brand new and longer than the other could the length effect something? I took them both off and adjusted the red knob so fuel came out of both. I just rebuilt the carbs this winter so all the jets should be free but I will go thru everything again. I have a feeling I didn't properly install the needle and seat. Is there a trick to making sure they are in the correct position.

 

[racerone]

The red knob is for manual operation of the electric primer.---Nothing to do with the carburetors filling up !

 

[zach103]

okay did some research on the red knob and know thats obviously not the problem as you mentioned. So seems to be the problem is either the float and/or the electric primer not working correctly.. So I guess my question would be how do I make sure the needle/ float and seat are in the correct positions?

 

[emdsapmgr]

The factory service manual has pictures of float adjustments for those carbs.

 

[zach103]

Totally forgot I had that manual. Thank you for the help. I got everything back together and the primer bulb actually gets as hard as it should be which is nice to see. I took it out for a test run in a small lake and want to double check some small things with you guys. The model is a J90TXCDC 1. What should be the appropriate WOT RPM. My tach was reading 5000 at wot. I know for a fact the throttle cables were adjusted to the carbs before the rebuild. 2. A couple of times on the test run it felt like the engine slipped from gear and would just rev with no movement. A couple of years ago the main shaft that connect the lower unit and motor snapped and was replaced. It maybe has 50 hours on it. No more than 100 that's for sure. Could it be slipping out. Or could the engine actually be too high causing a similar problem? Possible cavitating? If that's the right word. I will post a picture in the morning.

 

[emdsapmgr]

The target WOT operating rpm's is 5500 rpm's. Current thinking is that you are "lugging" the engine, by only running it at 5000. (It's ok to run it up to 5600.) So you are at least one prop size off. Your prop hub could be spinning-that could be the problem. Mark the brass prop hub and the outer part of the prop itself with a black marker. Run the engine. After, check the prop. The marks should still be aligned. If not, replace the prop hub. Since you are running the wrong prop, just replace the whole prop.

 

[zach103]

No Title

Okay that's makes sense I will do that. My prop size right now is 13 3/4 x 15 To replace the prop am I going up to a 17 pitch and different diameter? There are so many different options.

 

[zach103]

My prop size right now is 13 3/4 x 15 I did some research and understand to raise the rpms i need to drop 2" off the pitch. They also said if your boat is loaded with people or tubing which we usually do to go another 2" . So i think im going to go with the 14x11. Does this sound like a good place to start I found a couple online that are 13 spline and should work.

 

[emdsapmgr]

Not sure you want to drop all the way down to an 11 pitch. An 11 pitch would typically be found on a pontoon boat-not a planning hull. Is the tach on the right setting?

 

[zach103]

That's why I ask you guys first. I'm glad I didn't buy anything. So 13 possibly. My tach is at 6P right now.

 

[zach103]

So took it out today on the CT River. Ran great no real hiccups except when idling, If it idles a little higher than its set at it does fine though. I didn't pay too much attention going down river but going back up river it was only hitting 5000 rpm at WOT and only hit around 20 mph. Obviously the river has a part of that but on the way down i dont remember seeing going any faster than 25. Should I try to adjust the throttle cables and get the 13 pitch prop?

 

[emdsapmgr]

Agree: I'd probably do a visual inspection on the carbs when at wide open throttle. Make sure the carb main throat butterflys are completely open, or parallel to the length of the carb throat- first. You may be able to move the carb butterfly slightly by hand to make sure they are open. (they can be adjusted to over-rotate slightly so that they begin to close again.) Just be sure the engine has full wide open throttle capability. (You have to take the airbox cover off in order to see this) I'm still confused at the 15 pitch you are running. I rarely see a crossflow that can't run well with a 17 pitch. I could see a 15 pitch in a few instances. But a 13 is the direction you are headed and there may be something else going on. Have you done a compression test on the block? Maybe it's tired-low compression? The engine should pickup 300 rpm's if you go down to a 13.

 

[zach103]

Butterflies are not parrellel at wot well at least when the engine is off and throttle in that position. They are slightly closed but probably enough to effect it. I will adjust those. Compression test showed 90,98,98,90

 

[emdsapmgr]

The normal factory compression on that engine was probably around 100 when new, so your readings are within the normal 10% allowable tolerance. If the compression difference is between the two heads-it's even more normal. Factory compression on these crossflows could vary maybe 5 lbs between heads due to the way they were manufactured. Let us know if the performance changes when you get the carbs opening fully/normally.

 

[zach103]

Okay im glad the compression isn't too bad. i noticed that the butterflies aren't opening all the way because the throttle cable actually has about 1/2 inch of play. As soon as i pushed the end of the cable everything moved exactly where its suppose to be. I read that most cables have some play in them but does this seem drastic. Should I replace the cable or just adjust the cable so that it goes all the way. At some point I want to do the link and sync but need to gain some confidence. I do want to thank your Emdsapmgr for helping me through all of this so far.