turning 4800 rpm

[21 checked]

I have a 78 enchanter with a 76 200 rude original heads and carbs.I run it 2.5 under the pad with 12 inch set back With a 24 pitch 4 blade I can only turn 4800 at 58 mph.I just changed to a spinellie. prop 93239869458 I was told 21 worked to a 22 but still 4800.What is stoppin the motor what should my jets be? I have ran without cowl and no dif. need help.

[roadkill636]

I had the same problem with my 76,200
24p 3 blade raker=4700rpm
21p 4 blade=4700rpm
check to make sure the thermostats are still in there
I think that if pitch is the same, a 4 blade will turn a bit slower than a 3 blade
let me know if you need any parts,im parting out a 1976=200

[EMDSAPMGR]

What compression does the engine have? Is the tach adjustment setting correctly set? When you floor it do the butterflys open completely-to where they are level. High speed jets: .058 Idle jets: .031.

[21 checked]

The compr is 110 to 115 the butterfly are flat out haven't checked jetting yet those are behind the screw on the side of the carb right. I am going to check against another tach to check accuracy.Thanks for the jet sizes.

[baja200merk]

timin advancing? fire on all 6?

[21 checked]

Timed at 24 seems will check to see if firing on all cyl.

[B.Leonard]

12" setback and still 2.5" under the pad:rolleyes: Sounds like its burried. That motor will not rev with the prop burried. Try raising the motor. How much of a rooster tail are you throwing? If nearly no tail its too deep.

-BL

[21 checked]

I get about a 4 foot rooster and it is pretty loose. I don't think I can go much higher with stock lower.

[baja200merk]

wit 12 in back + what evers built into the boat id plug the two top holes on each side of the lower with epoxy and jack it up till you loose water pressure.. i would guess it will start to drop once your about even with the bottom.

kevin

[EMDSAPMGR]

If you have the original (uncut) 643/644 heads, stock compression should be around 125+. Still, your compression is solid. I'd probably look to the carbs. Have you been through them? I'd be sure all the passages in the carbs are open. Pull all the jets out and make sure there is no debris in any of them. Use carb cleaner to flush the passages. If you decide to fill the top two water inlet holes on the lower, you should also machine out the rib between the bottom two holes to provide enough water inlet area to feed the engine enough water volume for cooling.