Mercruiser 4.3 L Manifolds

[FiremistSLK]

I recently purchased a 1998 Chaparral 1830 Sport. It has a 4.3 L Mercruiser. I am not new to Mercruisers, but I have always owned V-8's. I noticed when checking out the engine bay before purchase that this V-6 does not appear to have a riser on top of the manifold? Other Mercruiser V-6's I see in photos DO have a riser! Am I correct? Am I missing something, or what??? Looks like the manifold just connects to a rubber boot near the transom. Can someone please help me understand what I am looking at? Thanks. JOHN

 

[Scott Danforth]

you probably have the problematic bat-wing manifolds.

replace them.

 

[Bondo]

Ayuh,...... Welcome Aboard,...... There was a time when 1 piece exhaust manifolds were used on 4.3s, but core-shift in the casting process caused thin spots, which lead to hydro-locked motors,....
Long ago, they went back to 2 piece exhaust manifolds, so I suggest you do the same,....
Look into the newer dry-joint 2 piece exhaust manifolds, which are the current issue manifolds,....

 

[FiremistSLK]

Oh, That's just great..... How much $$$ am I looking at to have them replaced? I have some mechanical skills but I am to old now to be climbing over and wrenching on a motor in a boat, so I will be droping the boat off at a local marina. I live in Central Florida.

 

[Bondo]

Oh, That's just great..... How much $$$ am I looking at to have them replaced? I have some mechanical skills but I am to old now to be climbing over and wrenching on a motor in a boat, so I will be droping the boat off at a local marina. I live in Central Florida.

Ayuh,..... Call around, 'n ask,.......
I do my own work, 'n labor rates vary widely,.....

 

[Scott Danforth]

paying marina prices for both labor and parts, you are looking at over $2500. if you do the work yourself, you are looking at about $750 for the dry break kit

 

[Lou C]

Barr Marine makes a nice conversion kit for the batwings and is a good deal cheaper than Merc OEM. The key to it is the down pipe adapters that allow you to use the same Y pipe.
I did I similar conversion on my OMC 4.3 with the OMC batwings. I used standard OMC/Volvo manifolds & elbows and bought the other parts needed from Volvo since OMC doesn’t stock them anymore. Same exact parts though. I had 3 sets of the OMC Batwings on mine (salt water you have to change every 5-7 years) & never had a problem with them. The nice thing about converting is that you can use standard Barr aftermarket manifold & elbow kits.

 

[Lou C]

PS that conversion kit I think is about $1200 from Barr. Check out Lighthouse Marine (Partsman) in Riverhead Long Island they do stock them & will ship to you. They are local to me so I just drive out there & save on shipping…

 

[FiremistSLK]

I know for certain that my 1998 4.3 mercruiser with the "Bat Wing" manifolds was used exclusively in a fresh water reservoir for it's entire life. The manifolds look almost new, as if they have been changed within the last few years. Is there any way to know that? I doubt they are 26 years old. There is no evidence of leaks on them anywhere. Does anyone know when the bat wing manifolds were no longer sold or were no longer available as a replacement? That info would help with a timeline as to when (or if) they were ever replaced. Where ALL of them no good? Did some of them provide for a normal service life (like 10 to 15 years in fresh water use)? I'm trying not to have to change them right now. Piggy bank is empty.....

 

[Scott Danforth]

some may last forever in fresh water.
many failed due to core shift issues (cant inspect them easy) and when that happens they kill the motor.

Merc started using the batwings you have in 1996 I think they quit using them in 2000

your motor is 26 years old. so why worry about a service life of 10-15 years?

 

[Lou C]

That’s the problem without some advanced visual imaging techniques you can’t tell if the casting is too thin or not. FWIW, I had 3 sets of the OMC version of the same thing over 15 years in salt water & never had a failure. But, that was replacing them proactively due to salt water use. All you can do besides converting yours before they fail is to pull the spark plugs & check for signs of water getting in the cyls (rust on spark plugs). How long do you expect to keep the boat?

 

[cyclops222]

Why I and others try to help people with the really odd engine problems. My favorite engine problem of marine engines is the UPDATING of the cams. But NOT adding the HIGH ENOUGH exhaust riser to prevent water from flowing BACK INTO the engine if doing WOT and suddenly going to idle speed.
ERRR ERR EERR engine will not spin. Pull out plugs and crank the engine easily as water sprays all over everything. Been on 2 cruise boats that did that. New / rebuilt engines. No or not followed instructions about adding the correct height risers.

 

[Lou C]

That is true, one thing that people should do is always measure static water line vs manufacturers specs. If you add weight to the stern because you added a bigger swim platform, or went from a V6 to a V8 your elbows could wind up too low. Merc makes spacers for this problem and Volvo makes taller elbows for the same thing.

 

[cyclops222]

Overloaded boats without a outboard ? You know water is being PUSHED into cylinders.

" My boat is real odd. Full load of people and the starter is real slow for several seconds. "
Battery checks out as excellent.

 

[FiremistSLK]

That’s the problem without some advanced visual imaging techniques you can’t tell if the casting is too thin or not. FWIW, I had 3 sets of the OMC version of the same thing over 15 years in salt water & never had a failure. But, that was replacing them proactively due to salt water use. All you can do besides converting yours before they fail is to pull the spark plugs & check for signs of water getting in the cyls (rust on spark plugs). How long do you expect to keep the boat?

Thanks Lou for the tip about checking the plugs for rust. Will do that tomorrow. Boat runs at normal temperature on the hose and water POURS out of the three water exits (prop and the two exhust ports on the outdrive). I do not intend on keeping this boat for very long.