Unable to turn over : 1991 4.3 OMC Cobra

[86Capri]

Hello,

Just picked up a 1991 SeaSwirl, Cuddy, with what appears to be a 4.3 L V6, and a OMC Cobra stern. Went to go turn the engine over by hand after removing all the belts, just to see and it moves a little, but seems to be binding. I checked it was in Neutral, the prop spins freely, I put it in forward and reverse and it also locks the prop, barely able to spin, just a little. Literally got this boat yesterday, and don't know where to start.

I have been doing research all day, and from what I can gather so far, because of the OMC, I should just take the boat out to an empty field and burn it down, never to speak of it again. Boats in pretty good shape, I would like to attempt to at least find out why I can't spin it, so I can try and get a compression test to see the health of the motor.

Any ideas?

Thank you very much.

 

[jerryjerry05]

Remove the plugs.(any rust, water?)
Then try turning it by hand.
That doesn't work??
Remove the drive and try again.(sometimes the upper gear set can lock up)
No luck?
Remove the starter and try again.(again it can lock up)

 

[Scott Danforth]

so you bought a non-running boat?

do you have the one piece bat wing exhaust manifolds on the OMC?

if so, the manifolds most likely leaked into the motor and froze it up.

pull the plugs, if you have rust, then pull the starter, try to use a prybar to rotate the motor with the ring gear teeth (never put a socket on the crank bolt)

if the motor doesnt turn over, you have a project on your hands.

 

[86Capri]

Remove the plugs.(any rust, water?)
Then try turning it by hand.
That doesn't work??
Remove the drive and try again.(sometimes the upper gear set can lock up)
No luck?
Remove the starter and try again.(again it can lock up)

Hello, removed all the plugs and it didn't turn any more sadly. That was the first thing I tried. I will be removing the drive next. Any ideas where the starter is located? I can hear the starter trying to spin, makes a loud clunk when I hit the key. So, that's a good sign of ... something. Thanks for your input.

 

[86Capri]

so you bought a non-running boat?

do you have the one piece bat wing exhaust manifolds on the OMC?

if so, the manifolds most likely leaked into the motor and froze it up.

pull the plugs, if you have rust, then pull the starter, try to use a prybar to rotate the motor with the ring gear teeth (never put a socket on the crank bolt)

if the motor doesnt turn over, you have a project on your hands.

Hello Scott,

Yes, I bought a non-running boat. I actually bought the boat sign / description, unknown. I purchased the trailer it was on, and when I got there, they didn't have time to remove the boat from the trailer, so I got the boat for free, title and all. Free boats are the most expensive.

It does not have the one piece bat wing exhaust manifolds. It has a normal looking, black volvo manifold. I will have pictures in about an hour.

All of the plugs had the same amount of surface rust on the base of the plug. No water came out of the engine when I removed them and they were not wet. This boat was last registered in 2015 (according to the sticker on the side).

I am expecting a project, and I have all winter thankfully. My wife is only an extremely good weather, boater/fisher.

Thanks for your help.

 

[86Capri]

No Title

Good news all!

I took the stern drive off and the engine spins now! I think what you guys call the gimbal bearing was actually seized to the little driveshaft! only able to turn that little bit I was able to turn the engine and prop. Excited to see if I can get the engine running.

Here are some pictures of this thing attached below.

Question, can I try and get the engine running without the sterndrive attached? With no gimbal bearing? What about cooling the motor? It looks like it has its own coolant tank?

Thank you all so much!

P.S. This cobra looks really ugly and bad, should I even think about trying to replace the gimbal, or figure out maybe a conversion to something better?

 

[Scott Danforth]

Sei conversion drive sold right here on iboats

 

[southkogs]

Yes, you can get the engine running without the drive attached. HOWEVER, you don't have a conventional ("typical" may be a better word) way to get cooling water to the engine without the drive attached - usually you do that with muffs down on the intakes. Your cooling system is also kinda' "wide open" without the drive on, so containing water is tough. So, be cautious about running more than a few minutes.

 

[HT32BSX115]

Question, can I try and get the engine running without the sterndrive attached? With no gimbal bearing? What about cooling the motor? It looks like it has its own coolant tank?

Thank you all so much!

P.S. This cobra looks really ugly and bad, should I even think about trying to replace the gimbal, or figure out maybe a conversion to something better?

Howdy,

Welcome aboard!

You can replace the gimbal. You'll have to find another used one though. Your pictures indicate that you do indeed have a "coolant tank" It's closed cooled.....meaning that the tank/engine block & heads is a closed system containing an anti-freeze-water (50/50) mix.

There is a hose from the transom mount that delivers raw (sea) water from the drive mounted raw water pump to the heat exchanger. It then exits the heat exchanger and goes to the exhaust manifolds and risers where it exits with the exhaust.

(you may also have a FULL system, where the coolant mix is also circulated though the exhaust manifolds. If that's the case, raw water from the heat exchanger "exit" is then routed directly to the risers and then overboard with the exhaust gases..........in that event, there would then be a blocking gasket between the riser and manifold to prevent mixing of the AF mix and raw water.......if you pay careful attention to the hose connections and routing, you can easily determine which type you have. Half systems (closed cooling block/heads) appears to be most common with small block systems.

With the drive OFF, you can connect a hose to to that raw water supply line to provide cooling water for on the trailer running.

Once the drive is removed, the engine can be run for as long as you like as long as you have "raw" water running into that hose so there will be cooling water for the heat exchanger and subsequently the risers and exhaust system.

If you do not provide cooling water, the rubber parts in the exhaust system will be destroyed quickly and before the engine actually overheats.

Regards,

Rick

 

[Lou C]

Used in salt water and had a bad bellows. Id take the drive to a shop and have them replace the driveshaft and u joints if the drive has oil in it and is not locked up. You can set the drive on a stand and try shifting it with the shift rod that goes into the lower gear case while some one turns the drive shaft clockwise. If it's not locked up and the prop shaft spins when shifted into fwd & rev get the drive shaft & ujoints replaced. Install a new gimble bearing, bellows and impeller. Re install the drive and try it out.

 

[86Capri]

Good news! The engine runs! Need to try and fix the carb though, after we turned it off it dumped fuel into the intake. Got the intake off letting all the fuel evaporate. Looks like the float is working properly. Any other recommendations?

 

[jerryjerry05]

2 or 4 bbl??
Should be Holly's.
IF??? it's dumping fuel after the shut down??
​The float's not working right.
Pull the needle and seat and see if there is anything blocking it or if it's bad?
The needle's tip could be deformed? Some were solid needs and some were made with a rubber tip.
The rubber tip can get a groove and leak.
The seat can do the same thing if it has an o-ring?