87 4.3 OMC Cobra Issue

[badchad450]

Hi all,

Great site, I have learned a ton just browsing. However, i couldn?t locate anything that pertains to my issues.

Please keep in mind, this is my first boat, and I have taken it out about 5 times, which brings my total boat rides to about 10!! So needless to say, I?m green.

The motor and drive seem to work great, no major issue and I?m running around 40-45mph at WOT.

I have noticed 3 issues that concern me, and each has happened on a different time, and different lakes, different days...

The first issue i had was when running near WOT (I always back off a little, maybe just a newbie thing?) The motor would almost cut out, and stall, but never died. It did this a couple time, slowed down, put in neutral, and off again without issue. This happened twice, on different days. Plenty of fuel, but maybe a pump or something? Maybe a cable issue?

The second issue i have noticed is that when running across the lake, my RPM will stay steady at WOT for about 10 min, but then the RPM dropped by about 700. There were a few "larger people on board, and was near the weight limit. What bothers me though, is that it was running fine at just below WOT for several mins, but then slowed down? I would think it would be able to maintain a consistent RPM. Maybe the weight and the water made it just bog down some?

and finally the third, this is a little harder to explain, while driving at about 3/4 WOT, the motor started making a clunking sound, and was losing power. slowed up, put in neutral and the clunking sound was still present. We needed to get back to shore, so I just nursed it for about 10 min, the sound went away, and the power was normal again???? I pulled the cover back, and there was a little smoke coming off the top of the motor above the carb(Air breather? I really don?t know, sorry)

Also, engine temps stay consistent, will be slightly above half way when running hot, and cools off when not?

So with the above issues said, the boat starts and runs like new today. no odd sounds, good oil pressure, everything seems to be in working order??? I am afraid that one of these trips I will be stranded. I want to fix before it cost serious cheddar!!

again, i apologize for the long post and newbie questions. I am a motocross guy, so I am not afraid of maintenance, and have enjoyed working on it so far. ( and I have never worked so hard on a toy, and that was just the wax!! Haha)

Thanks in advance for any help or ideas you may have.

 

[Joshua Nichols]

Re: 87 4.3 OMC Cobra Issue

and I have never worked so hard on a toy

Get ready to work harder..

Your first 2 issues sound like maybe a fuel problem.. Have ya done a tune up on it? The difference new fuel filters and all new ignition parts make on a boat are amazing.. Does it have a little 2 barrel carb on it? If so it is a very easy rebuild and worth every penny..

Now the clunking That sounds spooky to me.. Outdrive? Shift cable? Not sure on that one

 

[HT32BSX115]

Re: 87 4.3 OMC Cobra Issue

The first issue i had was when running near WOT (I always back off a little, maybe just a newbie thing?) The motor would almost cut out, and stall, but never died.

Howdy,


If the engine "cuts-out" ANYTIME you move the throttle, you may have a cable/control issue causing the ESA (electronic shift assist) module to actuate(when it should NOT)

If you're going to be doing your own work on your engine and drive, you really should get yourself an OEM OMC service manual. (don't wast your money on Seloc or Clymer manuals)

Also, to familiar yourself with how your drive shift systems works, have a look at the following link. It's describes the system pretty well. http://www.hastings.org/~stuart/cobra/

Your problem does sound like a carb/fuel delivery issue.


Regards, And Welcome aboard!

Rick

 

[badchad450]

Re: 87 4.3 OMC Cobra Issue

Thanks, its going in for a full service and tune up this week. I will have them do the carb as well(it is the 2 barrel). Hopefully that will cure the first 2 issues.

The clunking scared me too, but I cant figure what would do that, and then be just fine? I definatly think it was comiung from the motor, not the outdrive.

I will get the service done, and keep boating!

and BTW, i have been working on getting a manual, any tips??

 

[HT32BSX115]

Re: 87 4.3 OMC Cobra Issue

Thanks, its going in for a full service and tune up this week. I will have them do the carb as well(it is the 2 barrel). Hopefully that will cure the first 2 issues.

The clunking scared me too, but I cant figure what would do that, and then be just fine? I definatly think it was comiung from the motor, not the outdrive.

I will get the service done, and keep boating!

and BTW, i have been working on getting a manual, any tips??

"Clunking" can be due to not being all the way "in-gear" due to a defective lower shift cable (or adjustment").

If that's the problem, it NEEDS to be fixed or it will damage the the shift-dogs. If it's in the engine, it could be many things. you'll need to have someone listen to it and do a diagnosis.

I bought my OMC service manual from EBAY. There's a few people on there that sell reprints. They're not cheep.......but still better than the alternatives!

 

[Stanp1]

Re: 87 4.3 OMC Cobra Issue

I have the same engine 4.3 that had a similar issue at WOT. The gap in the points was too high. Get a mechanic to install new points and use a dwell meter to set the angle at 39 degrees +/- 2 degrees. Have the carb rebuilt, or buy and exchange your old one online. The timing is going to be set b/w 6 and 1 degree BTDC, depending on the fuel octane (87 set at 1 degree, or 93 set at 6 degree) Make sure your spark plugs are gapped at 35.

 

[badchad450]

Re: 87 4.3 OMC Cobra Issue

Stanp1, thatnks thats good info!!!

I will talk to my dude and have him check these out as well!

Hope to be ready for memorial day!!