unable to start '88 15hp Johnson

[OBJ]

Re: unable to start '88 15hp Johnson

Go back to my post that says open the low speed needle 2 1/2 turns. Then try to start.

 

[deaston]

Re: unable to start '88 15hp Johnson

Turns out that the gas leak is from the carb and there is a crack in plastic cover. I guess I must have tightened it down too tight, although I didn't think it was I screwed it on THAT tight. Either that or its always been cracked, but its hard for me to believe that I didn't notice it when I was cleaning it. <br /><br />Thanks for all your help!!! I bet that fixing this will solve my starting/idling problems.

 

[deaston]

Re: unable to start '88 15hp Johnson

One more question (yeah, I know... I keep saying that...)<br /><br />Regarding link and sync, when the throttle twist handle is full rotated to the slowest setting, the marking on the cam is right at the follower roller. Even playing with the twist knob at the end of the twist control handle, I can't get it to throttle back much more. Is this correct, or does something else need adjustment? I see some threaded pieces in inside the motor where the control cables enter the engine compartment. Do I need to adjust that?

 

[Kev]

Re: unable to start '88 15hp Johnson

Yes, it sounds like you need to adjust your link n' synch. Your throttle plate is probably opening way too soon.<br /><br />Here's how OBJ told me to do it for a 1980 9.9. I think yours is similar.<br /><br />"Setting the sync and link is easy. Look on the cam for a hash mark...it's cast onto the cam so you can't miss it.<br /><br />When the hash mark is aligned with the center of the roller (as you turn the twist grip) the throttle plate in carb should just start to open. You can watch the throttle plate shaft on the starboard side of the carb. It has a spring pin thru it. To adjust, run that allen head screw on the cam lever in or out as needed."<br /><br />(end quote)<br /><br />First, check to see if your low speed idle is set too high. There should be a black knob on the port side of the motor near the fuel connector IIRC (at least there was until 86 or so). Rotate it 1-2 turns toward SLOW and see if your minimum idle speed decreases. This knob also prevents the twist grip from twisting all the way toward the slow end of the spectrum if it is set too fast.<br /><br />Sounds like you will also want to adjust the cam roller so that it is farther away from the cam follower. That way your throttle plate should just start to open when the twist grip is set to the START position. If the hash mark on the cam follower lines up with the center of the roller just as the throttle plate starts to move, you've got the correct link n' synch setting.<br /><br />Lastly, the cracked carb cover will cause an air leak and most certainly cause your motor to run erratically. These motors are very sensitive to the air/fuel mixture.<br /><br />Try out these suggestions and let us know what happens.<br /><br />Happy Boating!<br />Kev

 

[deaston]

Re: unable to start '88 15hp Johnson

Just to be clear, I'm pretty sure I understand what I'm supposed to do regarding link & sync (cam roller starts to contact throttle plate right at hash mark). Problem is that when I have the twist control handle rotated as far as possible clockwise, the hash mark is already at or beyond the roller. Shouldn't I be able to rotate the throttle plate more toward the "closed" position. <br /><br />I have the newer motor with the idle speed adjustment at the very end of the twist handle instead of on the side of the motor. No matter what I do, I can't get the throttle plate to rotate closed any more than where the cam roller is right at the hash mark. Does that make sense? <br /><br />Looking at a parts diagram for names, it looks like you can make some adjustments with the "ball and socket" assembly as well as the "trunion". Of course, the next question is whether this is necssary and how much to adjust it. <br /><br />I am going to fix the carb leak but I'm waiting on parts for that. I think this other issue may be a problem given the importance of proper link and sync.