WOT Chevy 350 4BM??

F

Fishy McGee

New member
I've replaced the 305 in my 79 V-20 W/OMC 800 with an S&S remanufactured Chevy marine 350 with 4 bolt mains. I haven't been able to get a straight answer from anyone at S&S as to what WOT should be(I think I'm talking to counter sales people without a clue). I'm trying to size a prop and don't know what my WOT RPM's should be. Anybody out there in V-20 land have some info for me??? Please....Pretty Please......
Thanks
 
It really depends on which 350 you have. The early style 350's that used the valve cover bolts going around the outside of the valve cover should hit around 4,000-4,400 WOT. The 86-95's with the center bolt valve covers but non vortec heads should run anywhere from 4,200-4,600(some went to 4,800 depending upon which heads and cam). And most of the vortec engines should run from around 4,500-4,800, and the later MPI's went up to 5,000 or 5,200. These numbers are just rough numbers as drive combos and engine combos can affect the WOT range.
 
Thanks. I guess it's the older model. Valve cover bolts are on the outside. I was under the impression that the 4bolt main was a higher reving engine. Also, how far from "red line" is "WOT"? They are different right?
 
WOT is the max RPM's you can reach. Red line on an old style 350 would probably be around 5,000-5,500 RPM's. I would not reccomend runing it there for any length of time though. If it were mine I would prop it to run at 4,300-4,400 max RPM's with a light to moderate load. And most all of the marine engines are 4 bolt main blocks. The marine engines were normally modified truck engines, and most of the heavy truck blocks were 4 bolt main blocks. The real low HP engines would have been 2 bolt main blocks, but most anything over 230HP would be a 4 bolt main.
 
Hey man, thanks for the info. 4400 sounds safe to me too, so that's what it'll be. Zephyrhills Fl?? My buddy just moved back here from New Tampa....Beautiful area down there...and no witerizing!
Thanks again
 
Yep, just north of TAMPA, the big SH!TY. I remember back when TAMPA was just another city, about 25 miles away. Now you can't tell where TAMPA ends and we begin.
 
Yea, does seem like one really big suburb down there, but I'm used to that I'm in Northern Virginia/ Metro D.C. one big f'ing cluster f*@k
 
for what it maters, Ferm nailed the rpm specs on those motors. I prefered to let them turn a little on the high side of the rpm spec, alot depends on how you run the boat
 
Thanks to both of you guys for all the advice. I really appreciate it. My boat usage is probably 70% fishing(a lot of trolling ) and 30% tubeing/skiing. 70% salt/bay/in-shore and 30% fresh lake/river. I got the boat(79') and trailer(2004) for free. I've got about 2k into it including the motor. It's in the shop right now getting new lower shift cables and ball gears(too complicated for my taste) wich is going to be right around another 2k. Structurely the boat is sound, needs some attention on little stuff here and there, but what boat doesn't. I just hope I'm not throwing good money after bad, but 4-5k for a solid V20 with a fresh 350 doesn't sound bad to me.....Am I wrong. It's my first boat so I could be way off base for all I know. Again thanks for all the advice.
 
biggest issue you're going to have is with that outdrive. Those old stringer drives were marginal when they were brand new. If you really like the boat, keep your eye out for a damaged boat(cheap) with a Mercruiser(cheaper, more available) or Volvo( stronger but more$) complete drive set up. Keep in mind that the transom will have to be redone to accomodate a different drive. Several people have ditched the drive all together and gone with a bracket and outboard. the choice is up to you. Its probably cheaper in the long run to buy another boat with the right set up to begin with, but not many people on this site do things the normal or sensable way(we'd buy a newer boat if we had any sense). That drive is going to break sooner or later, they haven't made parts for it since the early 80's. For the 2 grand you are putting inot it right now, I'd be looking at other options. 2 grand isn't going to get it done, but it would be a good start
 
Unfortunatly I've already comitted to the work and it's due out any day. I'm not ready to give up on it just yet but any more pricey fixes come up I definitly will be looking to ditch the OMC. I could'nt even find a marina that would touch it anywhere near me and had to trailer it 90 miles to find this guy. I'm comfortable with the I/O set up because of the engines similarity to a car wich I'm used to. Any idea what the cost of having a transome redone to accomodate one of these other drives? Who does that kind of work anyway? And as always thanks for the adivce, it's definitly not falling on def ears....
 
the thing about replacing the transom on a stringer drive boat is the transom will need the thinkness increased. the original idea(and reason they ccall em stringer drives) is the engine is attached to the stringers rather than the stringers and transom. Its supposed to be smoother. The boat manufactures generally didn't put as much glass/wood in the transoms of a stringer drive boat as they did on a merc/volvo or outboard boat. As far a price goes, the skys the limit, especially if the stringers are rotten. Do a search on this forum, there are plenty of threads covering transom repairs/replacemnt. For your boat, a 1992 and up Alpha gen 2 drive set up, or Volvo SX/DP would be a good idea. You could use your existing engine as long as you swap over all the accesories. Look for a boat that has been damaged, repoed, sunk(fresh water only), Has a bad transom or floor. Look at dealers and repair shops. Its best to find a complete engine/drive setup if you can find one. You will need to know what to look for if you are mixing pieces, a lot of the merc stuff interchanges, but it can get confusing
 
Hey??... Not sure what to call you... Anyhow, thanks for all the info, you've helped me more than you know. I always wondered why it was called a stringer. Takeing your last post into consideration, I think I'll just keep up the maintenance on this one, run it for all it's worth and hopefully get a couple of good years out of it. After that if I still even want to set foot on a boat I believe I'll just look for something a little/lot newer that I can actually buy parts for....Striper season is just around the corner so there's no off season for this V.
Thanks again, I truley appreciate it.
 
don't forget with those stringer mounts you usually don't have a trim, only a tilt, operating the drive in any position other than all the way down will wipe out the ball gears. Some of the stringers had a trim system that used hydraulic motor mounts that raised and lowered the front of the engine for trim.​
 
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