scrab 21 7.4 454 mercruiser...54mph... need more top speed!!!

[scabvzla]

I have a 1991 21f scarab with a 7.4lts 454 carburated mercruiser with thru hull exaust an a bravo 1 sterndrive. Im looking to go a little faster with out spending a lot of money. Curently mi top speed is 54 mph wot @ 4800rpm with moderate trim, one person on board and 50galons of fuel... I want al least to top at 65 mph... Actualy i run a 14 x 23 stainles steel mirage prop. Thanks for the help!

[KSims1868]

I'm surprised to hear it isn't getting over 60 mph.
I can get over 60 mph in my 1989 22 Scarab Excel with a 350 Mag. Are you going by the speedo, or is this GPS speeds? If it's the speedo...it might not be accurate.

I run a 14 x 23 prop as well (Laser II). Maybe you need a little custom prop-work. What carb do you have on there? Have you done a tune-up lately? I would suspect you should be running faster than ME with a 454 in the exact same hull. From what I understand...my 22' Scarab is basically a 21' w/ a 1' swim platform installed (so they call it a 22').

[BY U BOY]

My 91 21 was topping out at 58gps with a 454 330hp that was a little tired. Did a rebuild with head,cam,exhaust and am running over 70 now.

Check you hull for a rocker or hook. Have someone look at you prop for trueness. Also pull your exhaust tips and check the transom for water,the boat may have gained some weight over the years.

[BY U BOY]

Originally Posted by KSims1868

I'm surprised to hear it isn't getting over 60 mph.
I can get over 60 mph in my 1989 22 Scarab Excel with a 350 Mag. Are you going by the speedo, or is this GPS speeds? If it's the speedo...it might not be accurate.

I run a 14 x 23 prop as well (Laser II). Maybe you need a little custom prop-work. What carb do you have on there? Have you done a tune-up lately? I would suspect you should be running faster than ME with a 454 in the exact same hull. From what I understand...my 22' Scarab is basically a 21' w/ a 1' swim platform installed (so they call it a 22').

Ksims,next summer if you see me around flag me down.Always nice to meet other scarab owners.

[KSims1868]

90% of the time I'm out in Clear Lake. I live in League City, so Clear Lake and the bay are my playgrounds. Occassionally I get up to the San Jac.

Where do you boat most fo the time?

[scabvzla]

Originally Posted by BY U BOY

My 91 21 was topping out at 58gps with a 454 330hp that was a little tired. Did a rebuild with head,cam,exhaust and am running over 70 now.

Check you hull for a rocker or hook. Have someone look at you prop for trueness. Also pull your exhaust tips and check the transom for water,the boat may have gained some weight over the years.

when you say rebuild, did you buy the stock parts o did you buy new performance parts, like a 4 barrel carb, aluminum heads, racing cams etc etc. like i say i top at 54 by gps

[scabvzla]

here are some pics

[BY U BOY]

Originally Posted by KSims1868

90% of the time I'm out in Clear Lake. I live in League City, so Clear Lake and the bay are my playgrounds. Occassionally I get up to the San Jac.

Where do you boat most fo the time?

most of my time is in clear lake.

[BY U BOY]

Originally Posted by scabvzla

when you say rebuild, did you buy the stock parts o did you buy new performance parts, like a 4 barrel carb, aluminum heads, racing cams etc etc. like i say i top at 54 by gps

Went ti roller rockers/lifter,Aluminum hi perf heads,zz502 cam,Intake,aluminum exhaust,srp pistons, hi volume fuel pump,crossover,and a new Barry Grant 830cfm carb Basically the only thing that is stock is the block

[scabvzla]

Originally Posted by BY U BOY

Went ti roller rockers/lifter,Aluminum hi perf heads,zz502 cam,Intake,aluminum exhaust,srp pistons, hi volume fuel pump,crossover,and a new Barry Grant 830cfm carb Basically the only thing that is stock is the block

haha of course yo do over 70, nice engine, im completely stock the only thing i changed was the exaust. the first thing im gona do is buy the aluminum heads and a new carb, that should give me an extra 70hp. combine that with a bravo one 14 x 26 prop, and i hope to go 65 at least. the problem is that i dont live in the us, so its real hard to find parts for this kind of engines here. Most people just run v6 outboards....

this are the only pics iv got of the engine on this pc