1987 5.7 omc outdrive

[Nick_1987 5.7 OMC]

Hey guys, need some help here. I was coming in from my last trip on the lake for the season and my outdrive blew out if no where. Not sure what happened but **** happens. My question is can I mix and match my 5.7 omc engine with other outdrive? Or do I have to replace it with another omc outdrive. And is it cheaper to try and rebuild my outdrive or just get a new one?

 

[Lou C]

well people have:
had their OMC rebuilt
converted it to a Volvo Penta SX (best solution but $$$)
converted it to a Merc Alpha using their Cobra conversion kit (much cheaper but unknown reliablilty).
I'm still running mine and picked up a good spare unit that I will have gone through as a back up.
When properly maintained they last a very long time. Mine's the same one that was on the boat when I bought it in 2002.

 

[Scott Danforth]

? Or do I have to replace it with another omc outdrive. And is it cheaper to try and rebuild my outdrive or just get a new one?

depends on what is wrong with your drive

 

[Nick_1987 5.7 OMC]

well people have:
had their OMC rebuilt
converted it to a Volvo Penta SX (best solution but $$$)
converted it to a Merc Alpha using their Cobra conversion kit (much cheaper but unknown reliablilty).
I'm still running mine and picked up a good spare unit that I will have gone through as a back up.
When properly maintained they last a very long time. Mine's the same one that was on the boat when I bought it in 2002.

thanks for the response. What do you think I should do? I’m on a budget of 2000$

 

[Nick_1987 5.7 OMC]

depends on what is wrong with your drive

I’m still not sure, I was cruising at 28mph than out of no where there was a loud clanking sound, lots of vibration than a crap ton of marbles in a washing machine. So for sure it’s beat.

 

[Lou C]

well the Volvo SX conversion is more than that, I priced it out using a used drive, used pivot housing and other things needed and it's about $5000.
the SEI conversion is approx $1800 but keep in mind that's an aftermarket copy of a Merc Alpha.
rebuilding the Cobra, probably $2-3K.
I am still running my original and bought a good used unit for less than a grand, so look around. For me I am very familiar with the Cobra if I had a good local place to rebuild it that's what I'd do. But it is not practical for most people.

 

[Lou C]

I’m still not sure, I was cruising at 28mph than out of no where there was a loud clanking sound, lots of vibration than a crap ton of marbles in a washing machine. So for sure it’s beat.

Did someone just change the gear oil in that drive? Because there is a right way and a wrong way!

 

[Scott Danforth]

I’m still not sure, I was cruising at 28mph than out of no where there was a loud clanking sound, lots of vibration than a crap ton of marbles in a washing machine. So for sure it’s beat.

could be bad gears, could be simply a broken u-joint.

pull apart and assess the damage

 

[Nick_1987 5.7 OMC]

Did someone just change the gear oil in that drive? Because there is a right way and a wrong way!

Well the boat was in the slip all year, no oil changing.

 

[Nick_1987 5.7 OMC]

well the Volvo SX conversion is more than that, I priced it out using a used drive, used pivot housing and other things needed and it's about $5000.
the SEI conversion is approx $1800 but keep in mind that's an aftermarket copy of a Merc Alpha.
rebuilding the Cobra, probably $2-3K.
I am still running my original and bought a good used unit for less than a grand, so look around. For me I am very familiar with the Cobra if I had a good local place to rebuild it that's what I'd do. But it is not practical for most people.

Hey Lou, so I found a complete volvo outdrive from 1981, would that work with my 1987 5.7 Omc engine ? Or I have a option to replace the 5.7 omc mount and outdrive to a mercruiser 260 with matching outdrive.

 

[Lou C]

nope that is the older style Aquatic drive system, the style that would work for the Cobra is the Volvo SX, 1994-2005 or so. The reason why is that OMC and Volvo went into a joint venture in 1993/4 and the OMC Cobra was redsigned to use cone clutch shifting. These were sold as the Cobra (up to '98) and the Volvo SX (up to 05 or 06), the units were identical except for color and manufacturer model & serial numbers. The parts changed were the drive, the pivot housing and a few other minor things. To do the conversion, you have to repace the pivot housing with the Volvo part, add an engine mounted impeller, and it may be necessary to change inner bushings in the trim rams. All in all if the boat is in excellent shape it makes sense since parts are available, and techs will work on them. The Cobra itself is not a bad drive, but now parts are not as available and many techs do not know how or are willing to work on them. But the cost, a good SX uses is like 3500-4400, then there are the other parts by the time you're done you're at 4500-5000. That's why I picked up a good used Cobra for less than a grand.

If you're interested in changing to a Merc drive, there is an easy way (Sterndrive International's Cobra conversion kit) or a more involved way (pull the engine, the Cobra transom mount, etc and replace all with Merc Alpha 1 Gen 2, which again is a lot of work but cheaper than Volvo, and makes your boat very repairable, and sell-able as well.

 

[Nick_1987 5.7 OMC]

nope that is the older style Aquatic drive system, the style that would work for the Cobra is the Volvo SX, 1994-2005 or so. The reason why is that OMC and Volvo went into a joint venture in 1993/4 and the OMC Cobra was redsigned to use cone clutch shifting. These were sold as the Cobra (up to '98) and the Volvo SX (up to 05 or 06), the units were identical except for color and manufacturer model & serial numbers. The parts changed were the drive, the pivot housing and a few other minor things. To do the conversion, you have to repace the pivot housing with the Volvo part, add an engine mounted impeller, and it may be necessary to change inner bushings in the trim rams. All in all if the boat is in excellent shape it makes sense since parts are available, and techs will work on them. The Cobra itself is not a bad drive, but now parts are not as available and many techs do not know how or are willing to work on them. But the cost, a good SX uses is like 3500-4400, then there are the other parts by the time you're done you're at 4500-5000. That's why I picked up a good used Cobra for less than a grand.

If you're interested in changing to a Merc drive, there is an easy way (Sterndrive International's Cobra conversion kit) or a more involved way (pull the engine, the Cobra transom mount, etc and replace all with Merc Alpha 1 Gen 2, which again is a lot of work but cheaper than Volvo, and makes your boat very repairable, and sell-able as well.

Ok apart from switching to the Volvo what’s the other option ? Swapping to a merc outdrive ?

 

[Lou C]

Yep there are 2 ways to do that. If none of the shops near you will work on OMC Cobras that’s an option that’s worth pursuing. Go on to SEI’s website and read up on their Cobra conversion kit

 

[Nick_1987 5.7 OMC]

Yep there are 2 ways to do that. If none of the shops near you will work on OMC Cobras that’s an option that’s worth pursuing. Go on to SEI’s website and read up on their Cobra conversion kit

Ok so I got the boat out of the water, removed the outdrive and split it in 2. The top half is absolutely fine, could use new seals. The u-joint is also in very good condition. But in the other hand the bottom half is absolutely (edit, come on man) lol all the gear are blown, bearings are shot and there is also a dent on the side of the. Almost looks like a bullet hole from the inside out. Anyways I think I’m gonna give insurance a shout and see what they can do. If they will cover I think I’ll just get a whole new drive, if not I’ll just get a new bottoms end. Opinions ? I’ve added pictures

 

[Lou C]

While your upper may look ok don’t forget that the bits of the failed gears are spread through the whole drive because the lube supply is share with the upper & lower. I would try and see if there is a local shop that could do it, it might be tough because of parts & special tools availability. You could try to put in an insurance claim but it looks like an internal failure not from hitting an underwater object which would be covered. So you have some choices:
Local disassembly of upper gear unit & cleaning and checking bearings & gears and replace the lower with rebuilt unit
Use the SEI conversion kit to convert the Cobra to an aftermarket copy of the Merc Alpha drive.
From what I’ve seen rebuilt Cobras go from 2500-3000; the SEI kit is cheaper but the quality of the SEI drives is variable some good reports as some bad. I guess you could also use their kit with a used genuine Merc drive.
other options cost more as I said in other posts it depends on how much the boat is worth to you. The Volvo conversion is $$$ but good for repairability and resale, converting the whole works to a Merc (pull engine, replace transom mount & drive with Merc) is probably cost wise the same or a little cheaper than Volvo conversion but is a lot of labor cost unless you can do all yourself. If you had to replace the engine or rebuild the transom this would make sense otherwise it’s a lot of extra labor.

 

[Nick_1987 5.7 OMC]

While your upper may look ok don’t forget that the bits of the failed gears are spread through the whole drive because the lube supply is share with the upper & lower. I would try and see if there is a local shop that could do it, it might be tough because of parts & special tools availability. You could try to put in an insurance claim but it looks like an internal failure not from hitting an underwater object which would be covered. So you have some choices:
Local disassembly of upper gear unit & cleaning and checking bearings & gears and replace the lower with rebuilt unit
Use the SEI conversion kit to convert the Cobra to an aftermarket copy of the Merc Alpha drive.
From what I’ve seen rebuilt Cobras go from 2500-3000; the SEI kit is cheaper but the quality of the SEI drives is variable some good reports as some bad. I guess you could also use their kit with a used genuine Merc drive.
other options cost more as I said in other posts it depends on how much the boat is worth to you. The Volvo conversion is $$$ but good for repairability and resale, converting the whole works to a Merc (pull engine, replace transom mount & drive with Merc) is probably cost wise the same or a little cheaper than Volvo conversion but is a lot of labor cost unless you can do all yourself. If you had to replace the engine or rebuild the transom this would make sense otherwise it’s a lot of extra labor.

I’m very mechanically inclined so I can do work on my own. I think I’m gonna take apart upper end and clean it all. Then re assemble and buy a new lower end and slap it all back together and replace seals. Should I check gimbal ?

 

[Lou C]

taking that apart is like taking apart an automotive differential, you have be able to set preloads and rolling torque, there's more to it than you might think. Unless you have to tools and experience you might end up with another blown up drive.
there are vids on a few sites that show what's done but I can't post them here.
Gimble is easy to check, they should turn very smoothly no roughness.

 

[Nick_1987 5.7 OMC]

taking that apart is like taking apart an automotive differential, you have be able to set preloads and rolling torque, there's more to it than you might think. Unless you have to tools and experience you might end up with another blown up drive.
there are vids on a few sites that show what's done but I can't post them here.
Gimble is easy to check, they should turn very smoothly no roughness.

Why can’t you post videos ?

 

[Lou C]

they are from a commercial site that sells parts, which then makes it against iboats policy.
do a search, hint...the place is located in Ontario Canada.

 

[kenny nunez]

Get a genuine OMC service manual. That way you will know about the special tools that are needed. Most likely you just need to wash out the upper. Since all the “V” style engines use the same lower you should be able to locate a rebuilt or used unit.
Sierra Marine has the seal kit for the upper and every else you will need.