Won't Start

[Angiecobra]

I got a 1987 OMC Cobra 4.3. with similar problem. Got new battery, new starter/selenoid, new assist selenoid, new fuel pump and filter. Actually I have two problems, first, boat will not start with key on start position. Tested ignition switch and is ok. Gauges work on run. Blower did not work, change a fuse and is working now. Tested cables for continuity test ok. Dont know what esle to do.
Well, second issue, if I hot wire at the selenoid, motor cranks and starts, but as soon as I let go it dies. Any help?

 

[Bondo]

Ayuh,.... Welcome Aboard,.... Please don't post in antique threads,.... I started yer own for ya,....

 

[lakenormangal]

No Title

I've got a 1990 Cobra OMC.
When you say hot wire, are you just using a wrench or screwdriver to jump the soleniod? Hum with a new starter and soleniod, you shouldnt have to jump it. And once its jumped, it should keep running. The starter will disengage after the motor is running and should have nothing to do with the engine continuing to run. Unless there's an electrical problem and that sounds like what it is.
And what is the history of the boat? Was it not starting? Are you a new owner of it?
One simple thing you may want to try, there's a big fat connector, the main cable connector, where many wires come together neat the top of the motor by the carb. This connector is like 2 halves. Pull that apart and clean the pins in those connections. In fact, go over all the connections and wires with a tester and make sure everything that should have electricity flowing, has current.
Now the problem could also be the 50 amp fuse that is connected to the soleniod ( its attached to one of the posts on the back of the soleniod and goes to the assist soleniod or the assist soleniod that is in between the starter soleniod and the main cable connector.
I have attached a picture of the cranking diagram. Go thru the system and check these fuses and connections.
Good luck!

 

[Angiecobra]

Thanks for the help with the post and the quick response. I had a Bayliner back in 1996, but it was two years old and I kept it for a year no issues. This 1987 Seaswirl Sierra Classic II with the OMC Cobra 4.3L was a gift from my neighbor. They could not start it and were frustrated with it and also needed the space in their driveway. He asked if I want it, I said yes, and next day he had it parked in my driveway. I don't know much about boats, but has always seen my Dad do all kinds of repairs, sometimes help him with tools. To make the story short. First, engine was stock and with a lot of DW40 on the spark plugs a good wrench and several days it got loose. Put in a new starter and fixed all cable ends. Change all spark plugs. New battery, new assist selenoid it cranked, but did not start. With carb liquid it will run for 10 seconds. Change the fuel pump and fuel water filter. Now it starts and runs.

I appreciate your help. I figure out what was the problem with a multimeter and a long wire. The yelow/red cable that ran from the ignition key to the assist selenoid on the back of the engine was not working. I ran a new cable. Also my ground on the negative pole of the battery needed cleaning. I took it apart. Now it starting with the key and it stays running. I just change the oil and oil filter. Today I started redoing soft spots on the floor and now lets see what else comes up. Want to take to the lake sometime before the summer is over. I need to do all the cushions, side panels and etc. Tips or suggestions will be appreciated. Hope nothing else is wrong with the engine. thanks again.