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50 cobra need more ponys

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Ken M.

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I have a 97 212 striper with a

I have a 97 212 striper with an OMC 5.0 ford cobra/300cmf holley carb. I am the 3rd owner and I know the motor has been rebuilt atleast once. There is no hr meeter so that is ????? The motor runs great but it eats a lot of 90 oct. As close as I can figure I am getting around 10 gal per hr at 3200 rpm cruse with a factory 14 3/4 X 17 SST prop at 3/4 trottle. Is this normal?? The book says that WOT should be 5500 rpm and the best I can get is 3900.
Should I try a 450cmf 4 brl or is there an aftermarket fuel injection system that is marine rated?? Also there is a ticking sound at idle. I think it is a sticky lifter or maybe the cam is going. Not sure on that yet.
Any ideas??
 
"Not sure if that's the ri

"Not sure if that's the right prop, but only 3900 revs sounds like a tune up problem. Hell, the secondaries of the carb simply may not be opening.

Ten gallons an hour for that motor sounds about right. My 360 Chryslers burn about that much in cruise mode.

Jeff"
 
"Thanks for the info Jeff. The

"Thanks for the info Jeff. The motor was tuned up last spring and the 300 cmf carb is a 2 brl so no secondaries. I am new to I/O so that 10 gal per hr sounds like a lot to me. That SST prop is the original and has a few knicks, I usually run a new Ballistic in the same size. If I am running light I put on a 14 1/2 X 19 and it does a little better. But still dont have the range I want. It has a 65 gal tank and I would like a 200 mile round trip range to get out where the big halibut are.
I am still thinking about fuel injection. Any Ideas??
Thanks Ken"
 
Fuel consumption on a boat can

Fuel consumption on a boat cannot be compared to automotive.Let off the throttle on a boat and you do NOT coast for half a mile like you would on a level road.It is called DRAG and there is lots of it.
 
"On a second thought, have a g

"On a second thought, have a good MARINA check it on their DYNOMOMETER to see if you have a motor in good shape."
 
".." I am new to I/O so th

".." I am new to I/O so that 10 gal per hr sounds like a lot to me. "

Welcome to boating! Exxon (and even greedier state goverments)love us!

...."The motor was tuned up last spring and the 300 cmf carb is a 2 brl so no secondaries."

That might be your problem right there: 300 sfm is tiny for a motor that size. Did someone toss that carb on there for "economy" reasons? If so, they wasted their money--and yours!

Jeff"
 
That carb is the one that was

That carb is the one that was on it when I bought it. I dont know if this is factory or an aftermarket thing. What do think would be the right carb for a 302 ford??

Thanks Ken
 
"I had a 20 foot older searay,

"I had a 20 foot older searay, (heavy boat).With a 17 pitch prop and an edelbrock 600cfm marine carb i was burning 6-7 gal an hour and cruising at 3200 rpm, and could easily hit my target 5000rpm without cavitation.
Change your intake and carb, and you will be pleasantly surprised. Then you can try repitching your prop to get into the desired rpm range.
My opinion"
 
"You're either over proped

"You're either over proped or underpowered; it should hit target RPM at WOT. 5500 sounds somewhat high, usually it's around 4500ish for a 302, re-verify that figure. Also consider that the cam , heads, compression, ect. may have been changed during the rebuild and may not have the power of the original motor. The 4brl. will give a little more but not enough to get from 3900 to 5500 for shure. Check ignition timing, may not have been set right during the tune-up. Other than major work to increase power, I'd try a smaller prop.; the decreased load will probably yield much better mileage and un-stress the motor. I'd think that boat should be able to cruise at 1/2 throttle or less."
 
"97 Cobra, do not quite belive

"97 Cobra, do not quite belive that, but 87 sounds better. RPM of 5500, 42-4400 sounds more correct. And the ticking sound - do you have a juming spark on the coil? 10 gal at 3200 is a good job through a 2bbl holley. I think there is more than a flooding carb here."
 
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