1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix ???

[Stan's Customs]

Decisions, Decisions...<br /><br /> Bought a 1988 5.7 Four Winns 200 5.7 Cobra.<br />Turns out to be a salt water boat, manifolds and risers supposedly changed in last 2 years. Might believe risers, doubt validy of statement regarding manifolds, scaley rust chunks evident in several places..thermostat area, drains on manifolds etc. Supposedly had gimble bearing and u-joint replaced at same time. Outdrive shifts and sounds good but has water in lower unit (milky white goo..) Engine (5.7) runs good, has "lots" of blow by, tachs out about 4600rpm.(17 prop) Trim causes engine to cut out when bumping up..ok when solid contact for trim advancement. Has the Ignitor conversion by Pertronix...was points I guess. <br /><br /> Bought a 1984 Four Winns 190, 898 Mercruiser (5.0) freshwater no salt. Lower unit noisy..guess to be gimble bearing..slight vibration , u-joint maybe ?? Lower unit oil black and thick, but no milk, obvious no recent service. Slight amount of water separated when draining lower unit, 2 jiggers maybe. 5.0 engine has new Holley 650 marine carb....dies occasionally may start immediately may take 4 or 5 tries...mystery right now, seems to be loss of fire. Seems to have small cam..not real strong on bottom w /21 prop but real strong thereafter..no blow by. Tach inop but revs higher than Cobra, guess 5000 rpm or more. Right exhaust manifold has freeze damage and bad external leak..left manifold has a crack..but no leak. Engine has fresh looking oil, no milky appearance. Possible that could change if run a while, but don't really think block is damaged. Has Thunderbolt Mercruiser ignition..<br /><br /> Engine on the 19' (5.0) is 2 piece rear main, engine on the 20' (5.7) is 1 piece rear main. Both are GM 4 bbl engines,.<br /><br />Both boats need about the same amount of cosmetics so that is not the issue. Although the 20' is only 1 ft longer it is considerably bigger. Has considerable wider beam and height, which may or may not be good. I own both these boats in the money, I can bail out of either one or both if I needed to.<br /> Since it seems to me you can pay a lot for a boat and have to practically rebuild it, or you not pay a lot for a boat and have to practically rebuild it..... <br /> I was wondering which one you guys would think is the best choice to spend time and money on...<br /><br />Decisions, decisions...OMC , Mercruiser ...Hmmmm..<br />fresh water, saltwater, 5.0 or 5.7, bigger or quicker...uh,o brain cramp..<br /><br />Thanks to all ...Stan<br /><br /> What "BOAT" stands for..."break out another thousand"

 

[Bondo]

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Mercruiser ...

 

[cc lancer]

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Vote number 2 for the Mercruiser.

 

[bomar76]

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Mercruiser.

 

[Don S]

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

How about a combination of both. Use the Mercruiser drive, transom shield, exhaust system, and ignition, just change over to the 5.7 engine. All the parts like alternator, starter, manifolds, coupler, bellhousing, etc are the same for the 5.0 and the 5.7. Keep the 5.7 flywheel on the 5.7.<br />The cutout in the transom is the same for the Cobra or Mercruiser drive, so changing one to the other would be no big problem.

 

[Stan's Customs]

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Hey Don...<br /><br /> I didn't know the cut out was the same. Does that hold true for a 1979 260 Mercruiser as well? I have a real good one that had u-joints and gimble bearing installed just before its last use 15 years ago. (Put in the body shop for repaint..they went out of business , skipped town, boat was stripped down ready for paint..."all" hardware disappeared. Barely got boat back from land owner). I used the motor in another boat, but still have most all the Mercruiser stuff including the log manifolds, flywheel and coupler.<br /><br />I'd "love" to get rid of the salt water stuff including engine..I have good stock earlier model 350 I could put the marine stuff on...."if the cutout is the same for the 260 Mercruiser drive as the OMC."<br /><br />That would be really good if it would work...I'd part out all the salt water stuff and and heve two good mercruisers. <br /><br />What about the shift interrupter??<br /><br />Stan

 

[Don S]

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

As I recall, the cutout is still the same.

 

[Lou C]

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Another thing to check out is the condition of the wood in both boats, meaning the floors, bulkheads, transom, and engine mounts. And what about the fberglass work, gelcoat, interior, etc. Although you will have an easier time with the Mercrusier, I would be careful about the potential for rotted wood in either one. Fixing wood rot is time consuming (but lots cheaper than fixing outdrives, assuming you can do it yourself). I fixed a small rotted area in the floor of my 88 200 and it took a while because the weather wasn't cooperating at the time. However, even using CPES and the best epoxy around, it didn't cost much to do. Some people just can't stand doing glass/wood work though, so you have to check that out.<br />I actually like the older style FW boats compared to the newer ones, the 84 190 has nice classic lines. Most newer boats are too much like today's cars, all the same and rounded with no identity.<br />BTW, checking the FW specs, the 88 200 is 20"9" long overall, the 84 190 is 18'8" long overall, the beam on the 200 is about 3 in wider. Don't know how important that is to you. I like the big sunpad and the integrated swim platform on my 88, good for fishing off of!

 

[Stan's Customs]

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Hello Lou..<br /><br />Yep, I like the big rear platform on the 1988 too...I think the transom to bow length is 19' something. The boat is a lot bigger and more cumbersom feeeling than the 1984 even though the dimensions don't seem to reflect the differences they seem to have.(it's a lot taller,too)<br /> In fact the bigger boat has a 17" prop and the 1984 has a 21" prop.<br /><br />Thanks to Four Winns encapsulated plywood the wood in both boats is in very good condition..very little to be done . The upholstery in the 1988 is better but the engine is smokier, much blow by. Similar cost factor for me...so I just discount the cosmetics to simplify the thread.<br /><br />Rigged the way they are the smaller boat seems like it will corner quicker to return for skiers and is a little faster...the bigger one will handle chop a little better and has more room, it's a little fancier too..has built in depth finder, stereo, bigger motor...but the salt has taken its toll in places that smaller boat doesn't have issues with.<br /><br />If I knew for sure that the old Mercruiser outdrive I have would fit the OMC hole...it would be a no brainer. I can build a powerful 350 that would be new and reliable, for very reasonable money. That's my business. and I'd have a real good outdrive that I know the histoty on that has never seen salt. The omc has salt in the drain vent holes by the waterpump...don't know what to do to clean a saltwater drive if anything..out of my field of expertise.<br /><br />I'm hoping this thread will address the salt issue...... and the fit of the two drives for sure. I'd be in hog heaven if I could change out the whole thing.

 

[Lou C]

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Stan<br />I have run mine in salt (moored in salt too for the season here, June to Oct) for the last 3 years, and it was run in salt before that too. It was originally a freshwater boat from the Midwest. I changed the manifolds last year (they were original!!) and the thermo housing. No scaly rust chunking off from what I could see in the intake or old thermo housing. Outdrive has no corrosion on it at all,(not in a marina with shorepower) our main problem is marine growth even when you use antifouling paint. Barnicles everywhere, in the pivot housing, on the bellows, etc. A real pain to clean up!!! All salt water is not the same in terms of corrosiveness. I have heard of engine blocks and heads rusting through after years of salt water (raw water cooled) use, but that is like after 10-15 years worth. So I don't think it is as big an issue, but hard to say not knowing what salt water it was in.

 

[Stan's Customs]

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Hey Lou...<br /><br /> From the looks of this one it was in salt water a long time (Go figure I bought in north Texas, caught me with my pants down)...Big chunks (almost quarter size) of scale/rusty metal in several places. I fear that the out drive may have a lot in it too, from the weep hole plugs you pull to winterize the top sides of the OMC drive each side of the waterpump ...the holes were plugged with salt when I removed the plugs.<br /><br />I've never seen the inside of a heavily used salt water rig...don't have a clue what to expect if it "is" damaged. I guess it's possible the motor and manifolds have "rusted plumb out" as my Granpappy would say.....and the lower unit passages plugged with salt ???<br /><br />Stan

 

[Lou C]

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Well this is the only boat I have had, so I really don't know what heavily used in salt looks like either, but big chunks and flakes of rust is more than 2 seasons of use. I have 2 seasons of 5 months in the salt on my thermo housing and there is no flaking rust at all. On my old manifolds, I didn't even know how many seasons they had in the salt (OMC one piece, no way to check riser) but I never had any overheating or water in the cylinders. Replaced them anyway just to be safe. If I was going to use that motor I might want to take off the manifolds and pressure test them, but since you said it has a lot of blow by (don't forget some is normal since they did not use a PVC valve on these, so all the blow by will be seen by the hoses that go up to the flame arrestor)I might do a compression test to see what is going on with it.

 

[Stan's Customs]

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Hi Lou...<br /> Blow by is caused by weak rings or excessive cylinder wear....so I will have to rebuild or replace the engine. I really don't want to repair any of the salt corroded rig, it needs so much...unless I can upgrade the whole thing. I really need to know for sure if the Mercruiser drive I spoke about earlier would bolt up to the OMC transom cut out.. as Don suggested. It would be much cheaper and I would have more confidence in the old drive that I know the history on. Plus I really perfer Mercruisers like the other posters....had good luck with them years back.<br /><br />If I had to replace the manifolds, rebuild the engine and rebuild the outdrive ...well the boat isn't worth it, even though I like it's comfortable size and ride.<br /><br />Now, if all I had to do was rebuild the engine and use my mercruiser drive and manifolds, it is a consideration,for sure. I wouldn't have more money in the boat than you could buy one ready to go for.<br /><br />In fact I started a new thread looking for transom template information. I can't find a thing anywhere on the net and don't have anything at the shop either.<br /><br />Stan

 

[Bondo]

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Stan,<br />There's little or No reason you can't put together Either of these boats, with the Mercruiser Parts........<br /><br />Granted, I'd dump All the saltwater exposed Driveline Parts......<br />Go Mercruiser........<br /><br />As far as the Hull, Saltwater Pickles the Wood.........<br />Freshwater Rots the Wood........<br />So, the 20'er Might be a Better Option..??..????<br />just transplant the Merc. into it......

 

[Stan's Customs]

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Thanks Bondo<br /><br />That's where I am leaning..the 20 footer is a little fancier, newer etc.. I was just worried about all the salt scale rust chunks. I don't know what the inside of the outdrive looks like but the manifolds and engine are sad.<br /><br />The Cobra shifts like a dream and is real quite, unlike many on the forum...but is was full of really thick milky oil. Drained it twice and refilled it, to clean it up...Don't know how bad the leak is (Cold front was comming and I decided to winterize before I could take it back out). I'd probably reseal the whole unit when I rebuilt the engine, which is another expense, even if it wasn't badly salt damaged...even I'd wonder if it would stand up. Parts for the mercruiser seem easier to find for the long haul too. 1979 model or not...<br /><br />Thanks again...Stan

 

[Bondo]

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

Re: 1988 OMC Cobra 5.7 litre or 1984 Mercruiser 898 5.0 liter...Best one to fix

The Cobra shifts like a dream and is real quite, unlike many on the forum...but is was full of really thick milky oil. Drained it twice and refilled it, to clean it up...Don't know how bad the leak is (Cold front was comming and I decided to winterize before I could take it back out). I'd probably reseal the whole unit when I rebuilt the engine, which is another expense, even if it wasn't badly salt damaged...even I'd wonder if it would stand up. Parts for the mercruiser seem easier to find for the long haul too. 1979 model or not...

Ayuh................<br />Scrap,+ Sell the OMC...........<br />That'll Pay for the Merc. Conversion........