Won't go WOT

[jbullen]

New here to this forum, also my forst OB motor. It is a 85 Johnson 90 HP V4. J90MLCOS The VRO has been disconnected, running on 50:1 pre-mix. When I got the motor it wouldn't crank, turned out to be a blown fuse. Starts right up every time now. Motor idles and goes into gear fine but when you get to about 1/4 throttle, that's all she's got. It just bogs down and surges a little but that's it. So far I have rebuilt both carbs, fairly certain they are completely clean. New fuel pump, using a portable gas tank, new lines, new bulb. The bulb does not go flat. What I have discovered is that if I pull off the top starboard plug wire nothing changes, I do get zapped a little. If I pull off any of the other 3 wires it drops RPM. I am waiting for the manual, it's ordered. Any suggestions on what this could be?

 

[HighTrim]

Re: Won't go WOT

Welcome to iboats.

I would get an inline spark tester. Set the gap to 7/16 of an inch, and see if the spark will jump the gap with a bright blue ZAP!! If that cylinder is not firing as you think, first try swapping the coil with a cylinder that is known to be firing. If all is now well, you need a new coil.



If the spark is fine, you will need to look into fuel delivery and compression. BTW, have you checked the compression on it?

 

[jbullen]

Re: Won't go WOT

I'll try swapping out the coil tonight with another cylinder and see if the problem follows before buying a spark tester. I haven't tested the compression yet, planning to do that as well.

 

[jbullen]

Re: Won't go WOT

I swapped the coils with another cylinder, now removing the plug on the top starboard drops RPMs but so does the same plug on the other cylinder with the coil from the first. Removing the plug wire from any cylinder now drops RPMS. What else could the problem be? Bad power pack? What fuel delivery problems could I have other than the carbs? I have checked all the lines, free and clear.

 

[HighTrim]

Re: Won't go WOT

If pulling all plug wires causes a drop in RPM, that means that they are all functioning as they should. You may of had a poor ground connection on a coil perhaps?

A better test is to have an adjustable tester, so that you can ensure that they are all firing over a 7/16" gap with a bright blue ZAP!!

 

[jbullen]

Re: Won't go WOT

OK, I got the manual. Compression is good and within specs on all cylinders. Spark jumps the 7/16" gap with blue zap. A couple of new thoughts (after reading through the manual) I did not adjust the floats on the carbs at all during reassembly, could that be causing the bogging? It is performing the same way as prior to the rebuild. Also I have figured out that the manual lever on the electric choke has been in the on position(for pull starting) when I switch it to the closed (normal operating) position the motor dies and cannot be restarted without switching back to the open position. Could this be a bad electric choke or back to carb problems? All help is appreciated!!

 

[jbullen]

Re: Won't go WOT

Update, I achieved WOT throttle this evening but still a few questions. If I have the electric choke in what is supposed to be the normal running position (inline with the body) it bogs on throttle advance, if I put it on the other position I am able to get to WOT. What could be the issue here?

 

[guy74]

Re: Won't go WOT

Have you tried pushing in on the key when it bogs down? Pushing in on the key does the same thing as moving the little red lever from it,s closed position(alined with the body of the primer valve). If dumping fuel into the carbs with the primer lets it run better, that indicates a fuel starvation problem. Clogged jets or improperly adjusted floats are the most likely causes.

 

[Reggie08]

Re: Won't go WOT

I have an 85 'Rude 90hp and experienced a similar problem one time. Turned out to be a mis-adjusted float on the top carb. Make sure your floats are parallel with the body of the carb with the carb itself turned upside down. Place a rag or towel in a bench vice and gently clamp the vice down onto the carb (just enough to hold it steady). Then check and adjust your carbs as necessary.

It might also be time do to a link-n-sync on your motor

 

[jbullen]

Re: Won't go WOT

I readjusted the carb floats and got them level before taking it out yesterday. Pushing the key in doesn't seem to help any when it bogs. I was kind of thinking the link and sink could help. How can I adjust the idle on this motor? Unfortunatley I got a SELOC manual and it's not very helpful in this department....

 

[jbullen]

Re: Won't go WOT

Are the carb rebuild kits the same for 1985 and 1986's of this motor? Mine is an 85 but the boat is an 86, when I bought the kits the guy knew the boat was an 86 but didn't ask what year the motor was. At the time I assumed it was also a 86.