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Need new motor for my Scarab, please help me do it right!

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Need new motor for my Scarab, please help me do it right!

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Old 08-20-2018, 08:41 PM
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Default Need new motor for my Scarab, please help me do it right!

Hi All,

I'm not sure what to do here. A month ago I grenaded a motor I put together (backyard build) and it sucks. You can read the saga here - https://www.offshoreonly.com/forums/...new-build.html

Based on what I learned from all of your feedback on that thread, I'm sure that I did my "new" motor no favors which probably led to its early demise. It didn't even make it one full season...

Long story short, I plopped vortec heads, comp xtreme marine cam, vortec intake, on a rebuilt Mercruiser 260HP block (non-roller). Block had new pistons, bearings, and rods (all factory cast parts). I ordered a relatively cheap rebuild kit (maybe cheap chinese parts? not sure...) for the bottom end at the time due to ignorance on parts.

I want to put a reliable, powerful motor back in the boat but don't want to make any mistakes this time. I'm wondering if the cast pistons are just not up to the abuse of my right hand and the bigger cam/heads and stress they put on the motor. Or if the cast parts are just fine and I just never tuned the motor properly?

I can get a vortec longblock pretty inexpensive, get the same cam and spring kit (except for roller motor), plop on my intake and have the same power (which was sufficient for me, I gained 9mph!!) and be back on the water pretty quick for pretty cheap. My question is, will it last if I get it tuned properly this time?

I've been told that I should go to a forged bottom end, is that true? The cost difference is VERY significant stepping up to a forged rotating assembly. I'm not opposed to doing it if that's the only way i can get the power I'm looking for and have it last.. Just wondering if a factory vortec roller block can take the added abuse of a larger cam and be reliable if tuned properly. The engine I just grenaded was a non-roller, early SBC 5.7 and this is the second time I've toasted it. The first go round, summer 2017, I put vortec heads and intake (factory cam) on the stock bottom end rotating assembly (7 seasons on that motor) and it blew up towards the end of the season. That's when I bought the cheap rebuild kit, tore it down and replaced parts, put new vortec heads on, and added the xtreme marine 12-236-3 kit which made it through 4th of July week.

Looking forward to your expertise and feedback, thank you!

Heath
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Old 08-20-2018, 09:10 PM
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Cast is fine for NA. If you are adding boost then its time to go forged.

I ran 10 PSI boost on a cast Scat 9000 crank and cast Speed Pro pistons for over a year. Then I started cranking the boost up a little at a time and I butted a piston ring.
Its all in your tune. You need a wide band O2 sensor or have the engine ran on a dyno before installing it in the boat.

Just realized, you may have butted a ring due to heat from it being so lean. Did you figure out what broke?
Were you running a retrofit roller cam or flat tappet?
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Old 08-20-2018, 09:27 PM
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Thanks for the advice, Pax! The cam was flat tappet. Can't remember which piston broke but it took a valve with it, cracked the block, broke cam in half etc.. Motor is toast! I'm pretty sure it ran lean as hell for too long, stupid me!

Would love to just grab a vortec longblock from jegs, summit, michigan motorz etc. and put a solid cam in and be done with it!
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Old 08-20-2018, 09:47 PM
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Here is the cam I installed.

​​​​​​12-236-3 - Xtreme Marine?
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Old 08-21-2018, 07:35 AM
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So when you say vortec intake, are you talking a dual plane or?
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Old 08-21-2018, 08:52 AM
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Originally Posted by 1986Scarab1 View Post
Thanks for the advice, Pax! The cam was flat tappet. Can't remember which piston broke but it took a valve with it, cracked the block, broke cam in half etc.. Motor is toast! I'm pretty sure it ran lean as hell for too long, stupid me!

Would love to just grab a vortec longblock from jegs, summit, michigan motorz etc. and put a solid cam in and be done with it!
You definitely want a roller block/cam. There is no reason to be messing with flat tappet cams anymore. Especially with all the shady oils out there, that can contribute to cam and lifter failure with flat tappets. If you do not feel comfortable building an engine, like you said just buy a short or long block 350.
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Old 08-21-2018, 09:05 AM
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https://www.summitracing.com/parts/m...3ct1/overview/
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Old 08-21-2018, 09:46 AM
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This would be my choice. Drop it in and live happily ever after with a wideband.
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Old 08-21-2018, 12:03 PM
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Much appreciated gentlemen! I didn't even see this motor when browsing summit earlier. Does it matter that it's not a "marine" motor? To my understanding, the freeze plugs are different and the cam may not be acceptable because of water reversion issues?

Further, here is the intake I currently have - https://www.summitracing.com/parts/sum-226018

I'm not certain what power I was making with the last setup (never dynoed) but based on the mph I gained folks have guestimated right around the power this motor you posted above is making.. I believe that should be plenty for a nasty little Scarab 1....

As for the intake and carb, is there a better intake that would make more power that you suggest? How about a cam? Also, the current carb is an old quadrajet that I had rebuilt, am I leaving power on the table?

I'm 100% open to spending additional on more aggressive top end if it will net me a significant increase and still be reliable once tuned. Would a new cam, springs, 1.6 RR, carb and a better intake be worth the trouble, cost and power I could produce?

Thanks a ton!
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Old 08-21-2018, 01:06 PM
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Originally Posted by 1986Scarab1 View Post
Much appreciated gentlemen! I didn't even see this motor when browsing summit earlier. Does it matter that it's not a "marine" motor? To my understanding, the freeze plugs are different and the cam may not be acceptable because of water reversion issues?

Further, here is the intake I currently have - https://www.summitracing.com/parts/sum-226018

I'm not certain what power I was making with the last setup (never dynoed) but based on the mph I gained folks have guestimated right around the power this motor you posted above is making.. I believe that should be plenty for a nasty little Scarab 1....

As for the intake and carb, is there a better intake that would make more power that you suggest? How about a cam? Also, the current carb is an old quadrajet that I had rebuilt, am I leaving power on the table?

I'm 100% open to spending additional on more aggressive top end if it will net me a significant increase and still be reliable once tuned. Would a new cam, springs, 1.6 RR, carb and a better intake be worth the trouble, cost and power I could produce?

Thanks a ton!
The stock 350 long block that Mercruiser used is a car engine. The water pump, starter, alternator, TBI or Carb....etc everything on the outside of the engine are what makes it a marine engine. I think the oil pan may also be different.

The intake you have is fine, I have the Edelbrock version of it on my 383. I thought quadrajets required a special flange to mount, yours looks like the Holley style square flange?

You could stick a Holley Marine carb on it.
https://www.summitracing.com/parts/h...2670/overview/

These are the cam specs in that motor

Cam Type: Roller
.495/.503 lift
220/224 duration
@ .050, 110 degrees LSA
Using 1.5 rockers

Are you using the stock manifolds? Through hull or out the drive?
My cam is bigger than that, and as far as I can tell, I am not reverting water. Stock manifolds, exhaust running out the side of the boat. Boat has not been on the water, since my cam swap. Running in the driveway on the hose, I have no reversion. I am also EFI, which I think plays into that some, since some tuning with the EFI can calm the cam down at idle.
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