How fast with OMC v8?

[TWICEBIT]

Hello everyone,

I am new to the site and to Hot Rod boating. I've been looking over the site for a couple of weeks and I am impressed with the amount of knowledge here. I am considering a 21' Eliminator Daytona tunnel that has a stock OMC 4.0 liter V-8. I know there are mixed feelings about these motors but I would like to hear some opinions of how fast this boat should be assuming the motor is in a good state of tune. The motor is stock (including power steering) with the exception of a high perf elec. fuel pump and the oil injection has been eliminated. The hull has a manualy adjustable lift plate. I know prop choice and set up has a lot to do with the performance but I would like to know what range of speed I could expect.

Thanks for any help,
Bryan

[TWICEBIT]

I forgot to add that the motor has a low drag lower unit with low water pick up.

[Instigator]

Stock it will probably run 80 to low 80's.

Great motors, near bullet proof but like gas.

Ton's of potential and great torque for a big heavy boat like that.

If you snoop around the site a bit and pay attention to who is talking/typing you'll find out a lot of good info on these motors.

Lots of guys have had them that were already way out of tune and in poor shape to begin with.
They are normally the ones telling you they're junk.

Takes a lot of paitence to get a 20 yr old V-6 2 stroke into tune then think if you make it a 8 that most have no clue on how to work on.

Gary

[Matt Gent]

Ours is a 3.6 300. It is stock as far as we know, though it gives compression readings in the 145psi range.

85mph on the limiter with a 26 4-blade chopper and decent holeshot.
90mph @ 6600 with a 29SRX, harder to plane off.

It will go 110-120 miles @ 70mph on 44 gallons of gas.

Our propshaft is about 1-1/8" below the running surface for lower unit longevity. I think there is probably another 5mph in lifting the engine and playing with props. I'd love to try a 30 cleaver and raise the engine an inch and a half.

[Instigator]

Ours is a 3.6 300. It is stock as far as we know, though it gives compression readings in the 145psi range.

85mph on the limiter with a 26 4-blade chopper and decent holeshot.
90mph @ 6600 with a 29SRX, harder to plane off.

It will go 110-120 miles @ 70mph on 44 gallons of gas.

Our propshaft is about 1-1/8" below the running surface for lower unit longevity. I think there is probably another 5mph in lifting the engine and playing with props. I'd love to try a 30 cleaver and raise the engine an inch and a half.

Very impressive!

Had no idea that thing ran that good.

Miami Dave has a 30 for a JohnRude he'd let you run if you hook up.

I also have (he is borrowing) a Spinelli DR-4 29" that I bought for cruising and Dave really likes it too.

Would help you pop on plane w/the extra blade.

I don't like the SRX's on tunnels.

They're only 14 1/4" dia and lose bight when you get the motor up.

My River Rocket ran a best of 98 w/one but spent more time in low 90's if everything wasn't perfect.
I spent a lot of time over trimming the motor with that wheel trying to carry the bow.

Sold it.

Being that low too, there is definately more there!

P.S., lose the limiter :)

[TWICEBIT]

Thank you guys for the info. That is exactaly what I was looking for. If I end up with this boat or another one, I am sure I will have more questions.

Thanks again,
Bryan

[RUDERIOT]

I just can't get the idea of doin' a V-8 outa my head...:eek:

[Li'l Toy]

Matt Gent above is my son. One thing we learned on this site is that you need to bolt the lower unit. Apparently OMC lower units generally, and paticularly the ones on the V8, aren't nearly as tough running a surpace prop as the Mercs. The rear bearing carrier will "work" because it isn't real tight in the bullet, and make the back of the bullet egg-shaped. Drill 4 holes at each 90 degrees around the lower unit through the bearing carrier, bolt it with 1/4-20 x 1" flat head machine screws and locknuts. And I have lost the upper left one three or four times even with the locknuts--I finally bought some stainless wire, and I need to drill and wire the nuts.

I agree you need the big, torquey motor to run the Eliminator. I don't think a 280 would be nearly as nice day-to-day. DFI insted of 8 carbs would be nice, and I just had my first problem getting a part, but there are plenty out there used. Oh--if you are in salt, use some kind of lube on the shaft that carries the butterflies for the port top two carbs--mine has frozen up twice, and the second time was when the computers said that Bombardier had no more throttle body assemblies.

You already have the VRO out of it--everyone agrees that is necessary.

[Li'l Toy]

It is a 22 year old dinosaur with 30+ year old technology. Until I can afford a 300xs (which is limited even lower and I will probably never afford), 6800 is fine with me. Some folks on this board say to hold it down well below that.

[Riverratt]

Do you still need to pin the newer carriers? My 92 V8 has the bearing carrier that has the 2 bolts out at the back of the carrier instead of the 4 bolts back inside.

[Instigator]

I just can't get the idea of doin' a V-8 outa my head...:eek:

Mark, call me today if you get a chance. 772-879-7652

RiverRat, absolutely! Pc of cake to do and be glad to walk you through it if you like.

LilToy, great info!

I have a buddy in Ky w/an 8 on a 22' Talon. Slightly warmed over and turns it right at 7K.
No issues so far but he has been though his to start with and that is part of turning any of them up.
He has another one in process that he is leaning on a bit ;)

Also agree on the differnce between HP's and torque.

Rick Gillman out in Az has one on an Eliminator and he turns it 10K :eek:
It is a lake boat that he has also drag raced very succesfully ;)
He is also a tinkerer though.

Racer (Al Stoker) is the best on this board for honest info on your limitations and would take what he says as gospel.

If you are staring to see issues in part availability I'd buy a spare and moth ball it. Hell, they're almost free down here since we all know what junk they are ;)

Something else to consider... for the fraction of a new motor you could mount Wayne Taylors EFI to it. Have'nt hooked mine up yet but it's a pretty amazing pc and is almost infinately tunable through all of the rev range.

Better yet...., buy your spare then let Dr. Montague grind on that block while you wait on your boxs to show from Wayne :p
400 HP's for $5 or $6K ;)

[Riverratt]

Thanks Instigator. Mine is in the process of getting a new propshaft and carrier installed right now. I broke a propshaft.

[TWICEBIT]

Thanks again for the info guys. I am having a friend inspect the boat in person hopefully today. I have not seen it in person yet (it is 5 hours away). If it checks out good I will make my decision on it very soon and check in for more info on minor mods to be done.

Thanks again,
Bryan

[Dutch]

if you wouldn't haul sheep around in your boat it wouldn't break.

[Big Johnson V8]

Mine was set at 1" below the pad. Would run in the low 90,s with a 4 blade cleaver 29. The thing really came alive when we put unlimited pack on it, better hole shot and awsome mid-range. It was built by Dragon Master Outboard and he has several of them sitting in the shop, I have never had problems finding parts.

[outboards4life]

Mark, call me today if you get a chance. 772-879-7652

RiverRat, absolutely! Pc of cake to do and be glad to walk you through it if you like.

LilToy, great info!

I have a buddy in Ky w/an 8 on a 22' Talon. Slightly warmed over and turns it right at 7K.
No issues so far but he has been though his to start with and that is part of turning any of them up.
He has another one in process that he is leaning on a bit ;)

Also agree on the differnce between HP's and torque.



Rick Gillman out in Az has one on an Eliminator and he turns it 10K :eek:
It is a lake boat that he has also drag raced very succesfully ;)
He is also a tinkerer though.

Racer (Al Stoker) is the best on this board for honest info on your limitations and would take what he says as gospel.

If you are staring to see issues in part availability I'd buy a spare and moth ball it. Hell, they're almost free down here since we all know what junk they are ;)

Something else to consider... for the fraction of a new motor you could mount Wayne Taylors EFI to it. Have'nt hooked mine up yet but it's a pretty amazing pc and is almost infinately tunable through all of the rev range.

Better yet...., buy your spare then let Dr. Montague grind on that block while you wait on your boxs to show from Wayne :p
400 HP's for $5 or $6K ;)

spun my dads up to 8700 with a 30 cleaver on the Daytona. Ask Charlie how fast it went passed his STV at the Rumble last year.:D

Like Gary says as long as it is tuned right they will run hard for a very long time.

[wideopen23]

not trying to hijack this thread but I have this same set up with a v8 275 and I can not get mine to come out of the hole. With a 24 raker the motor goes to 2500 rpm and takes forever to get on plane then takes off like a bat out of hell. Any of you guys had this problem?

[wideopen23]

ttt......

[Airboater]

not trying to hijack this thread but I have this same set up with a v8 275 and I can not get mine to come out of the hole. With a 24 raker the motor goes to 2500 rpm and takes forever to get on plane then takes off like a bat out of hell. Any of you guys had this problem?

try a different prop ,do you have a planing foil ,might help keep it from cavitating plus
plane faster

[wideopen23]

there is a planing foil on it, I am going to try a diffrent prop on it this weekend to see what happens, it just seems that a 275 on this type hull with a 24 raker should pop it right out of the water.

[RUDERIOT]

It should come out pretty aggressively. There is absolutely no way a 24 Raker will stall that motor at 2500 if everything is right. Link & sync the carbs first & make sure you're getting timing advance. Then make sure what carbs you've got & check the air bleeds to see that they match the carbs. If not get the ones that the book calls for & you're done.

[baja1000]

My silverwing did the same thing till I put a Red fuel pump on it. I put it to if I remember right to 80 psi

[wideopen23]

I have synced the carbs timed it, checked compresion everything seems to be in order. The only thing I noticed tonight is that the idle jets are 26 and according to BRP they should be 30? Would this make a diffrence?

[RUDERIOT]

Go by the carb. body #. and then of coarse that's not to say that somebody somewhere along the line didn't change the tubes. The bleeds must be for the body you're using them in. I know this isn't always true but it just makes the whole process of tuning the bottom end so much easier. You haven't burned it down yet so I doubt you have a major vacume leak anywhere.

The smaller idle bleeds would make it slightly fatter than it's supposed to be at idle. Does it smoke much when you take off after idling 15 min? Can you feel/hear it miss or does it just bog at 2500? Push the enrichenner when it's doing this & see what happens. It's awfully hard to diagnose a problem that I haven't heard.

[wideopen23]

it does smoke idleing and seems like it coughs from time to time idleing. But I have tryed clearing it out before taking off that doesnt help, I have tryed pushing the enricher but it just bogges worse. On take off I can floor it the motor runs to 2500 and stops untill on plane. The carb # on the body is 393574, well I cant find this number any where, the number that is stamped on the metal plate on the side is 397479, which calls for i-30 m-36 and 65d.
What is in it is i-25 m-36 and 65d.

[wideopen23]

Ttt......

[RUDERIOT]

it does smoke idling and seems like it coughs from time to time idling. But I have tried clearing it out before taking off that doesn't help, I have tryed pushing the enricher but it just bogges worse. On take off I can floor it the motor runs to 2500 and stops until on plane. The carb # on the body is 393574, well I cant find this number any where, the number that is stamped on the metal plate on the side is 397479, which calls for i-30 m-36 and 65d.
What is in it is i-25 m-36 and 65d.

When a Looper sneezes it's usual cause is a a vacuum leak, damaged reeds... or both. Composite reeds ain't very tough & won't stand much sneezing.

[lilabner]

You can get a perfect idle by using a Magnehelic gauge, and 8 special fittings per OMC engineering drawings..The fittings, or tubes screw into the intermediate jet hole and the jet goes in the other end of them..a fitting in the side of the tube goes to the gauge via vacuum tubing..You have to be in the water, in gear, at idle, and get a reading on each carb..you adjust the reading with different idle jets..not for the amateur, and very time consuming, but worth it in the long run..this is done mainly for the big carbs on the early engines..

[RUDERIOT]

We're about to make this a lot more convoluted than it needs to be. We're trying to make the motor plain the boat, not make it run silky smooth.

The reason I place so much stock in having the correct by the book air bleeds for the carb body & tubes you're using is that it's just the easy way to pretty perfectly fine tune the idle, off idle/bottom end of the r.p.m. range. You can of course do the trial & error thing but why? One thing I will tell you about those carbs is to be sure & keep an eye on the emulsion tube projection-height. They can & some times do move. This movement DRASTICALLY changes the main jet requirement. I had my motor jetted about on the edge for drag racing & all of a sudden #1 plug showed it was a couple sizes fat & to make a long story short, the rest of the motor had .086''s in it & #1 ended up at .076''. This about drove me nuts so I stuffed & set up another big bore to replace it with. When I removed it the pullover looked to be taller in it than the rest & it was. By about 0.125''. How that tube moved up is beyond me but I've since made a gage to check 'em.

[gearcase]

eliminator 1989 ran the u know what out of it. nose cone low water pick up. pissed off a few merc stokers with it. back in the day!

[wideopen23]

I will get the jets all back to stock settings and see what happens, Ruderiot, are these emulsion tube projection-height things the same as the pullover tubes? How do I pull them to check for same sizes?

[RUDERIOT]

No. The brass tubes (pullovers) that are attatched to the carb. body & reach down into the float bowl carry the idle & midrange fuel for those circuits. By the way, there are at least 2 differant sizes of each tube, maybe more. The midbores for some reason have larger i.d. pullovers than the bigbores do, or at least that was the case with the ones I have & I switched the larger tubes into the bigbores. This is one way to fatten up the lower midrange & has allowed me to "cruise" the motor at a constant 35-3800 with race jetting & not burn it down. Much above 3800 & it starts to sound real "crisp", not a safe thing to do to a motor with big bores, if you care anything about it.

The emulsion tube is the one you see when you look into the bore of an assembled carb. Look them over real well cuz also, as well as moving up & down (up will make it fatter & down will make it leaner) with a given main jet size, I've seen them erode on the back side of the plastic tube. This makes 'em fattern' a hog.