Need info on my new purchase OMC 4.3L Cobra

[BoatingTimbo]

Re: Need info on my new purchase OMC 4.3L Cobra

Good point. Been so focused on fuel system i've not looked into spark/timing issues and probably the shop didn't either? I've got the boat back now. Don't trust that it's Carb and don't want to buy a new carb and find out that's not it. Pretty expensive next step in ruling things out!

 

[Gary H NC]

Re: Need info on my new purchase OMC 4.3L Cobra

Ok...you said you are not a mechanic but rebuilt the carb?
Was everything set to specs on the rebuild info sheet?Float adjusted to specs?

This should be a simple 2bbl Rochester carb with 2 idle mixture screws in front,correct?

The too small of fuel pump deal was crap...those carbs only need about 5 or 6 psi to run correctly.

 

[BoatingTimbo]

Re: Need info on my new purchase OMC 4.3L Cobra

I'm no mechanic! I just know enough to get myself into or sometimes out of trouble. Enough knowledge to do a lot, but when it comes to rebuilding a carb i let the shop do that. I made sure they had a factory manual for this engine so they could set everything to spec. so confident they did that right.

They performed the three main tests on fuel pump that turned out ok and ruled out fuel pump (pressure, flow, suction) since everything was working to spec.

I'm trying to find another local or mobile marine mechanic to come check it out since i need this delt with. Can't take the family too far from shore for fear of breaking down.

I did find a new carb from Lordco parts for $230 so if it is carb thats not bad. I just don't want to spend that to find out it's something else!

 

[Gary H NC]

Re: Need info on my new purchase OMC 4.3L Cobra

This is probably what you have if you end up needing a carb.
http://marinecarburetor.com/Y39RochesterCOT.htm

I would have the points,condensor and rotor replaced,timing and dwell set then test it.

 

[Gary H NC]

Re: Need info on my new purchase OMC 4.3L Cobra

Here is the factory service manual...It is priceless!
All the trouble shooting info,specs and everything you will ever need for that setup.Including the crucial lower shift cable adjustments you will need sooner or later..
Email the seller and tell him Gary in NC sent you..

Ask him to verify the serial number off your drive for this manual.

He ships fast too...

http://cgi.ebay.com/ebaymotors/1989...0QQitemZ200352521925QQcmdZViewItemQQptZMotors

 

[BoatingTimbo]

Re: Need info on my new purchase OMC 4.3L Cobra

sorry to keep bringing this up... BUT... now i've got a manifold water leak! damn! leaking from/around the front side starboard engine mount. I guess i'll have to have this checked out and hope it's not cracked block? oil is not milky.

 

[danond]

Re: Need info on my new purchase OMC 4.3L Cobra

A manifold leak from the engine mount is not a manifold leak. It's a cracked block.

 

[BoatingTimbo]

Re: Need info on my new purchase OMC 4.3L Cobra

ooohhh... this boat experience just keeps getting worse and worse!

 

[BoatingTimbo]

Re: Need info on my new purchase OMC 4.3L Cobra

Guys, who's got a 4.3L OMC cobra close to my 1989 -- need to know if your running the mechanical fuel pump or electric fuel pump. Right now the boat is using electric fuel pump but looks like there's the mounts for the mechanical fuel pump on the side of the block. Are all the blocks set up with the mounts for mechanical pump but used electric pump?

can't seem to find the appropriate fuel pump for this engine... please help. thanks.

 

[sea wolf]

Re: Need info on my new purchase OMC 4.3L Cobra

sorry to keep bringing this up... BUT... now i've got a manifold water leak! damn! leaking from/around the front side starboard engine mount. I guess i'll have to have this checked out and hope it's not cracked block? oil is not milky.

I think you need to investigate this issue further. There's no point in sinking money into fuel pumps, etc. if the engine is toast.

 

[gregstukey]

Re: Need info on my new purchase OMC 4.3L Cobra

www.ishopmarine.com has Bombardier/OMC parts catalogues for OMC oem parts.

also to access Bombardier's online parts catalogue go here

http://epc.brp.com/ - just plug in your email (dont worry i receive no spam) and choose stern drive in the pull down menu---choose year, engine, model # etc to see exploded views of the parts for your engine/drive.

i think intake manifold/fuel pump is about half way down the list...

 

[BoatingTimbo]

Re: Need info on my new purchase OMC 4.3L Cobra

Thanks guys. the water leak i had checked out and it's the frost plug on the block has cracked so a pretty easy swap out. Just need to figure out the appropriate fuel pump for this motor...

 

[newbie4life]

Re: Need info on my new purchase OMC 4.3L Cobra

.....the water leak i had checked out and it's the frost plug on the block has cracked...

That would make my day I think.

I have a similar issue to yours, carb wise (although it's a 2.3L OMC) I have taken it to the local "old pro" up the road from me... my electric choke is junk, and I need to find another one (rochester 2bbl -- hey, wait a minute... aren't these the guys that made the "quadra-junk (jet)" for my old chev???)

Just one more idea to throw into the pot. I know you said the carb was rebuilt, maybe they overlooked it???

 

[BoatingTimbo]

Re: Need info on my new purchase OMC 4.3L Cobra

i'm having someone else dig into the carb in detail. Hope that solves it. Still trying to figure out the correct fuel pump for these engine though??

 

[BoatingTimbo]

Re: Need info on my new purchase OMC 4.3L Cobra

Sorry to keep bringing this up but the mystery of the fuel starvation continues! I had another mechanic do the frost plug which was my issue with the water leak (thank goodness it wasn't the block!!).

He rebuilt the carb again b/c he said the original rebuild a about a month ago at my marina they used the wrong rebuild kit! Now after testing last night the problem is still there but worse! Now i can't rev over 2,000RPM for longer then 30 seconds before it dies out from fuel starvation.

I started a new post specific to just the starvation issue with more detail... but i need help! This is costing me way to much and know one seems to have a clue how to pin point the problem!!

here's the new post: http://forums.iboats.com/showthread.php?t=326819

 

[loosechange]

Re: Need info on my new purchase OMC 4.3L Cobra

I have 2 complete 1988 4.3 OMC if you need help pm me doug

 

[BoatingTimbo]

Re: Need info on my new purchase OMC 4.3L Cobra

finally solved the problem... after everything it was only the rubber pick up fuel hose in the tank. after inspection each time and turning the anti-siphon valve / coupler back onto the tank it was twisting the hose and kinking it -- causing my fuel starvation problem.

now i'm back and running.

thanks for all the help and suggestions.

now i'm going to figure out why i can't get to max WOT of 4,200-4,600. I'm only hitting 3,800'ish with 14.5x19 prop. Not a big deal at all.

 

[jasport]

Re: Need info on my new purchase OMC 4.3L Cobra

I've got this same engine (1987) and recently resurrected it from the brink of extinction. The correct carb kit's a must, but I was astonished to find the previous owner was running the wrong plugs. Plugs that are too long can cause misfiring too deep in the cylinder at higher RPM's. The manual suggests AC plugs, but I prefer the cross-referenced NGK's. Did it, done it and she runs like a champ to 4400 RPM. Not bad for a 22 year old boat!

Also, your timing may be advanced a couple of degrees too much....

Something new to try. Hope it helps.

 

[Amsterdutch76$]

Re: Need info on my new purchase OMC 4.3L Cobra

What? Take your boat somewhere else. You don't want your mechanic guessing at what's wrong then spending your money to diddle around.

There's no way for them to diagnose your boat as having a "small fuel pump" by looking at it or listening to you. That's just dumb of them to even speculate. Does he even know what that means? I sure don't.

Did he check timing? Distributor cap/rotor/plugs? Carb adjusted properly? Throttle adjusted properly? Is the prop the right size/pitch? Is it bent? Is the boat full of water (under-sole foam can definitely absorb water)? Plugs OK? Compression OK? on and on.

I have an OMC Cobra, I can speak from experience I think. Here are your steps:

1) get an original OMC service manual. Find them on ebay.
2) read it, cover to cover, repeatedly
3) learn to service your own drive and engine.

If you plan on keeping this boat, 1, 2 and 3 are a MUST. If you want a "take it to the mechanic and they'll know what to do" boat, sell this one and get one with a Mercruiser drive.

Don't get me wrong, OMC Cobra drives are fine to run if you can service them yourself or have a local marine mechanic who knows and enjoys OMC. If not, you're screwed. Your mechanic is going to break your stuff and you'll be left with the bill.

I'm not sure you're on this Forum anymore but I see you may have the same boat I just bought and would like some info? I think your knowledge of these engines could help me out...Thanks

 

[Amsterdutch76$]

Re: Need info on my new purchase OMC 4.3L Cobra

I've got this same engine (1987) and recently resurrected it from the brink of extinction. The correct carb kit's a must, but I was astonished to find the previous owner was running the wrong plugs. Plugs that are too long can cause misfiring too deep in the cylinder at higher RPM's. The manual suggests AC plugs, but I prefer the cross-referenced NGK's. Did it, done it and she runs like a champ to 4400 RPM. Not bad for a 22 year old boat!

Also, your timing may be advanced a couple of degrees too much....

Something new to try. Hope it helps.

I just purchased a 1988 Larson Senza OMC Cobra 4.3l. 4 Valve V6 and looking to change the spark plugs and wires....wondering if you can point me in the right direction so I can find/buy the correct parts? Any info on what the best tools to use size of socket and such would be greatly appreciated ...Thanks