Mercury 1150 outboard with bugs

[crawford81]

I have what I believe to be a 1975 Mercury 115. When I bought it all internal wires on starter side of the motor were corroded. I replaced them all except the hot and ground wire. They were in great shape. I cleaned the carbs and and replaced the plugs. Hooked the battery up and turned the key and nothing happened. So I turned key to on position, touched solenoid with two screw drivers and the engine turned good. Checked compression and all cylinders hit around 115. So I choked the engine and it cranked right up. I hooked water to it and it pumped water good. I cut the engine off. Next day I went and bought new solenoid hoping that it would fix my key problem. It did. But I lost fire on all my plugs. So I put the Old solenoid back on and the key continued to work. And the plugs started firing again. So I took it too the lake and it performed like a champ, great top end speed and idled good. Got back to the dock and I let it idle for about 3 minutes. I decided to make another round just to make sure it was running right. Gave it throttle and it died down, so I pulled the throttle back to idle and it idled good. Gave it gas again and it died down again. Got it back to idle speed and pushed in idle button on controls and gave it gas and it revved up great. Went back to idle speed, put it in forward and it ran good again. Any suggestions about this motor?

 

[CharlieB]

Re: Mercury 1150 outboard with bugs

Sounds like you have two totally separate problems, the starter solenoid, and an idle/acceleration issue.

First the solenoid, if the 'Old' solenoid is now working, do not expect it to last, it may have a 'burnt' section on the contacting washer inside. It rotates with every use and will soon be around to that burnt spot again and fail to crank the motor. I suspect you got the wrong replacement part. Solenoids can have one or two small terminals, if they have two then there is also two different types of and the wrong one will not work. Have your model and serial #'s handy and check here for the correct part #, then make sure that your replacement parts cross-references to it.

http://www.mercruiserparts.com/mercruiser_parts.asp

As for poor acceleration, a motor can rev just fine in Neutral, even with one cyl not firing at all, yet fail miserably once in gear. The very first step in troubleshooting is to pull all of the spark plugs and take a good look at them to see if any have an excessive amount of carbon build up that can cause it not to fire reliably, if so replace the plugs and check to see if any carbs are flooding, causing the plug to foul. With the motor OFF and the trim set to dead level, open the throttle to WOT, pump the primer bulb and hold it firm while looking into each carb throat to see if ANY fuel is leaking. If so, order carb rebuild kits and get busy.

Next, leave the plugs out and ground all the plug wires to the motor block. One at a time, test spark on each using an adjustable gap spark tester set to 7/16 inch. You need a hot blue arc on each to reliably fire under load. A weak orange or no spark on even one cyl will still rev in Neutral but cause problems once under load.

Check these couple things and repost your findings.

You may find a copy of the correct service manual at one of these links.

http://1manual.com/Mercury manuals/Service_Manual_Index.html

http://forums.iboats.com/showthread.php?t=309079&p=2072211#post2072211

 

[Chris1956]

Re: Mercury 1150 outboard with bugs

Actually I think you have three problems. The first two are as Charlie described. If that motor has a distributor, it requires +12VDC to two adjacent terminals on the switchbox. If one or both do not get good voltage, you will have no spark. I recommend you check them out. The red wire is hot all the time. The white wire comes from the keyswitch and supplies voltage when you want the engine to run.