BLOWN OUT BAHA BOAT BUILD BLUES

HangerWide

Member
BLOWN BAHA BOAT BUILD


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Project description:

Repower a 1997 Baha 290 Mach 1 Open Bow that was purchased at a discounted price due to loss of short block integrity. The original block suffered interior expansion cracks to both cylinder banks just above the lifter bores from freeze damage.
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Project Goals:

  • Determine a realistic budget

  • Prioritize decisions and expenditures as 1: reliability 2: efficiency 3: performance gaines
  • Appropriate & Realistic power for application. (500HP/ 1800-5400rpm range)

  • Improved overall performance from factory power package.

  • Overall build to create strength and durability in a engine that produces a minimum of oem power then apply low boost for reliable power gaines and performance increase

Focus points of engine components:

  • Estimated Build Cost = $5200.00 - $5700.00 / Max out of Pocket $7000.00 Allowed

  • Initial Machine Work for surfaces, cleaning, and inspections.

  • 454Ci cast block W/ Increased rotating assy strength and main studs

  • Large Oval cast heads W/ increased valve train strength and head studs

  • Intake - Forced injection W/ aluminum aftermarket dual plane, single carburetor, manifold

  • Fule - high output mechanical with ⅜ minimum supply lines

  • Carburetor - Holley marine grade blower carb with mechanical secondaries 850cfm

  • Replace Stock ThunderBolt V ignition with more reliable setup.

  • Oil Supply - High Volume Pump



Selected Components

  • MKIV 454CI Short Deck

    • Standard Bore

    • Stock Crank

    • Scat I-Beam Forged Cap Screw Rods

    • Icon Forged Flat top pistons, Fee floating pin

    • Speed Pro Tri-metal Performance Bearings
-871 heads

    • Mercruiser OEM Roller Cam

    • Lunati Retrofit Hydraulic Lifters

    • ⅜ Push Rods

    • Comp Cams Stainless Steel Roller Rockers (standard ratio)

    • Comp Cams Adjustable Guides Plates
-Intake and Fuel Management

- Performer RPM 2.O

- Holley / Quick Fuel M-850

- Baker engineering / ProCam Marine Mechanical Fuel Pump

- Kenne Bell / AutoRotor 1.5L Twin Screw SuperCharger

-Ignition

- Davis Unified Ignition Marine HEI with Custom Advance Curve

* (14 degrees / all in @ 2800)

- Talylor Cable 8mm Spark Plug wires




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Project Details:


The 1997 Baha Cruiser 290 Mach 1 Originally came equipped with a Mercruiser 7.4L Bravo III engine and drive package. In Brief detail this package consist of a GEN VI 7.5L cast block with small oval port cast heads with open chambers and a volume listed as 118cc, a cast 4bbl intake manifold supported by a Weber/Carter AFB with mechanical secondaries rated at 750CFM. The Short block is a 2 bolt main with cast steel 4.00” stroke crank, 6.135” forged press pin rods and cast pistons supporting 5/16 top and second rings and 3/16 oil rings. The Cast Pistons are flat with a slight dish but i was not able to find the exact volume of the pistons. The heads are 156 casting small oval ports with non adjusting stamped rockers and guide plates listed as 118cc and having Valve size 2.06 intake, 1.72 exhaust. The head gaskets are mercruiser MLS gaskets. The camshaft is a Mercruiser Marine roller cam with 215/217 duration@.05 the centerline is 110 and a lobe seperation of 115.4 The engine is listed to have 8.1:1 Static Compression and with and intake close time listed at 69 the dynamic compression is roughly 6.5 assuming 118cc heads and a 3cc dish. The engine is rated at 330HP.

Detailed Specifications Link:

https://www.perfprotech.com/blog/tech-specs/mercruiser-bigv8-marine-engines-specifications

To replace the engine I chose a Mark IV block that i pulled from a 76 motorhome with roughly 86000 miles on it. The owner stated that he had the engine rebuilt years ago from a spun bearing and the crank has been turned on the main journals. After breaking the engine down I confirmed bore size as 4.25” and the cylinder walls were in very good condition. The crank was as stated with 1 size under on the mains. I ditched the flat tappet cam, lifters and all the bearings then delivered the bare block, crankshaft and heads to the machine shop for inspection. The shop reported that all components passed magnaflux inspection and were usable components. After discussing the build project and my desired goals we chose an approach for required machine work. I had the block cleaned including oil plugs pulled and galleries brushed, hot tank treatment and a jet wash cycle then the cylinders were honed for use with moly rings. The crank was turned and polished with a final measurement of 10 under on the rods and 20 on the mains. I had the heads resurfaced and the valves cut and seated, the guides were inspected and noted well within tolerance. The springs and retainers were replaced with the springs from the mercruiser engine head seeing as i intended to use the mercruiser cam from the damaged engine. We discussed oversize valves and extensive head work but the machinist felt the money would be best spent elsewhere as the marine exhaust manifolds are rather restrictive to benefit from larger valves. On the way home i stopped by the car wash and pressure washed all the parts using a degreaser and a few brushes. At home i prepped the block and heads for paint. After painting and a quick recleaning I treated the parts with wd4 and covered the engine with plastic wrap and spent a week or so researching and ordering parts.


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Everything went together rather well. I chased all threaded holes and cleaned all hardware with parts cleaner and a wire wheel. The main caps and heads received stud fasteners and all valve train components were coated in assembly lube and sprayed with dry moly film. I followed many threads and instruction from this site in regards to clearances while putting everything together and feel rather confident in the build and was rather proud of myself.


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Once assembled I Ran the engine naturally aspirated for break-in and confirmed timing. I had good oil pressure at 60 psi above 2000 rpm and no noted temperature issues. SOOOOO i took her to the lake. It started good and ran without issue while in the no wake zone but once i tried to plan off i could get to about 2800 and that all she had. I checked timing it was good so, checked fuel supply and pressure and volume were good. Then i noticed my oil pressure had dropped and there was oil noted in the builg. I wasn’t far from the loading ramp so i returned at just above idle throttle, at idle my oil pressure was near zero and just off idle I had almost 20lbs. Back home I found that the issue began when the secondarys would open then the engine would flood, severely flood, I checked the plugs and they were black and fouled. I checked compression and THIS is where the trouble was found. 80 on all cylinders.


It took several days to find the issue but the low compression comes from a miscalculation on deck height where i ordered pistons that do not have the accurate compression height. I ordered 1.27 pistons and needed 1.52 pistons. My current configuration deck height is .395 in the hole so my compression is hammered. I suspect that with the low compression i was way over jetted and flooded the cylinders causing the rings not to seat and push excess crankcase pressure to the pan pushing oil out the rear main. I intended to bump my static compression slightly by using flat top pistons in place on the cast pistons in the factory block as i needed a higher static ratio to achieve the desired dynamic ratio with the cam i have, but now i'm at a critical turning point in my build. The cost of piston and rings is far more than replacing the rods or crank so I would like to keep the pistons. I am sure the crank will need turned again and all the bearings replaced as well as the whole engine cleaned, im sure I ate the bearings, I cut the filter and there was metal in the element.


As i assess myself over this build I can account for many mistakes, such as failure to check deck clearance after installing the rotating assembly, or checking the measurements of the rod and pistons together. Hell i didn't even check the length of the rods when i got them to make sure they were the correct length that i intended at the time. I did clean all the parts as instructed from several of grumpy's threads. I spent lots of time and money on the proper tools for checking clearances i just missed it. I don't feel i rushed the build… maybe i was just overwhelmed or over my head but one thing's for sure. I was real proud of my self as i thought I had done well with my project. Setting goals, researching all the options and parts, reading reviews and setting realistic performance goals (i hope). I know its no 1000hp cannon, but i thought it was a modest build with a little flare and would be a great engine from my boat… im not all that confident in it anymore. Embarrassing


All that aside this thing needs to come apart. So im looking at my options, i have spent a lot on rods and pistons and they are forged components. The crank is stock so to me the best results for the money would be to replace the crank with a stroker crank and take advantage of the added performance, BUT there is no way to make up the distance with crank stoke alone. So Im buying rods either way. Now Its not much more expensive to just replace the crank with a 4.25 stroke and run 6.385 rods to put me at .020 deck height and a .020 gasket to achieve .040 quench and adequate compression. If i do not replace the crank i can run 6.535 rods and that puts me -.005 out the deck. I can make that up with a gasket to get somewhere between .035 and .038 but to get to .045+ from a gasket that will match well with boost I would have to go to copper head gaskets which are awesome but expensive. About the same cost as buying a crank, either way i need to balance the rotating assembly So in the end I’m about to spend 1000$ on the bottom end and would like some opinions and suggestions on where to go with the engine at this point. I am not worried about the expense as much as i am worried about reliability and cost vs gains. Seeing as it’s coming back apart this is a good time to review the all of the parts and see if i am even close to what i intended to build (obviously not in the compression area) is there alternative cam specs that would be better suited for this engines intent? Are there other obvious issues that i am missing? Any suggestions and PRO TIPS are welcome and wanted. Im open to changing anything that needs to be corrected either for better performance or especially for reliability. I have other specific information if needed, I know I left a lot out in terms of specific details that i can provide if needed.
 
If You go Stroker Big Block Chevy You will need to loose the Kenne Belle Twin Screw Supercharger as its only 1.5 liter displacement and sized for a 454 Big Chevy.

Keith Black makes his line of Forged Pistons. ICON Pistons. Nicely made.
Very Strong. Affordable.

Kinda at a breaking point.
Fix the 454.

Go 496 with no supercharger.

Build a Marine 502 .
Build a 540.
Build a 572 Big Chevy.

Need to tear down your 454 and see what good and damaged.
Full assessment.
I know it's tough.
Pretend its a job and not yours.
Emotions left out that way.
 
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I used to be a Big TRW Piston Fan user.
Speed Pro owns now or Federal Mogul corporation.

Kieth Black Pistons are made nice and a good value.
Modern thing ring package pistons tend to cost more.
Keith Black Hyperuentic & Base forged Icon pistons are one the few left with GM stock 5/64" piston ring sizing.
Thin rings have advantages.
Give 7-8 more HP at the crank.
Not Racing so I do not see a huge advantage.

Better pistons made like CP Carillo & Diamonds.
About $1000+ per set.
Not Racing so I don't see the Need for them.
 
GREAT PICTURES!

lets drop back to basics, I can only base suggestions on the facts you tell, me,
is that a standard 9.8" block or a tall deck truck block,
Id assume its a standard 9.8" deck block
use the existing pistons and crank, upgrade the rods, (yes this might require a re-balancing, check the rod weights are similar or get the crank balanced to new rod/piston weight,
https://www.summitracing.com/parts/sca-6653522a

piston pin to deck height pistons-1.27
dechkl.png

Much stronger than stock aftermarket 6.535 rods are available rather reasonably priced

https://www.summitracing.com/parts/sce-t13325
get the quench near .045

once you get the longer 6.535 rods, measure the true piston to deck height before ordering head gaskets, most un-decked blocks measure 9.818- 9.823 not 9.8 exactly
find_tdca.jpg


http://garage.grumpysperformance.co...on-ring-info-youll-need.509/page-2#post-71538

http://garage.grumpysperformance.co...in-height-compression-height.5064/#post-66240

http://garage.grumpysperformance.com/index.php?threads/can-you-plan-for-quench.11298/#post-51325

http://garage.grumpysperformance.com/index.php?threads/types-of-crankshaft-steel.204/

http://garage.grumpysperformance.com/index.php?threads/head-gasket-related.1859/#post-50617

http://garage.grumpysperformance.co...ore-clearance-on-your-block.14251/#post-72471

http://garage.grumpysperformance.co...ting-rod-balancing-question.13403/#post-69706

http://garage.grumpysperformance.com/index.php?threads/precision-measuring-tools.1390/#post-68861
 
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If You go Stroker Big Block Chevy You will need to loose the Kenne Belle Twin Screw Supercharger as its only 1.5 liter displacement and sized for a 454 Big Chevy.

Keith Black makes his line of Forged Pistons. ICON Pistons. Nicely made.
Very Strong. Affordable.

Kinda at a breaking point.
Fix the 454.

Go 496 with no supercharger.

Build a Marine 502 .
Build a 540.
Build a 572 Big Chevy.

Need to tear down your 454 and see what good and damaged.
Full assessment.
I know it's tough.
Pretend its a job and not yours.
Emotions left out that way.


With those suggestions that's an easy choice. I started with a goal to build a forced induction motor. So retaining the 454 ci displacement with proper compression and deck height is the target. The requiered rod length is 6.535. is there any issue with clearance to expect? Rod angle conserns?
I am glad that you recommend the icon pistons as that is the pistions I have. I preferred the 5/16 ring pack for this build.

Thank you for your advice. You offered a different perspective that helped me sort out the options.
 
obviously you need to check clearances carefully,
as connecting rod profiles differ between part numbers,
but I never had and significant issues using similar SCAT 6.535 rods,
so you might just want to call SCAT to talk with the tech guys
tell them what your tring to accomplish ask for their advice
Phone: 310 370 5501
the blocks deck height, minus the connecting rod length, minus 1/2 the crank stroke. will equal the required piston pin height
http://www.enginebuildermag.com/201...ton-compression-height-and-crankshaft-stroke/
deckh.jpg

deckh.png

http://garage.grumpysperformance.co...onnecting-rod-rod-length-too-stroke-info.510/

http://garage.grumpysperformance.co...od-rod-length-too-stroke-info.510/#post-10311

http://garage.grumpysperformance.com/index.php?threads/big-block-chevy-info.710/#post-72463

http://garage.grumpysperformance.co...g-block-for-stroker-assembly.2855/#post-77609
 
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When I get it apart I will check the exact height again before dropping the crank, and BEFORE ordering parts.
There are a few options for rods in that length.

The link you are the scat rods I was plan on getting.

There are a few different brand rods that are a little more but not out of the budget.

Scat- 2200A series are the same as the ones above but have the ARP2000Alloy bolts. There about 100$ more.

K1- technoylogy are about 660$ ARP2000Alloy and are about 60g lighter (avertised)

Callie's compstars - 660$ and have the L19 bolts

Between the options I see the Scat-2000a Series is the better value based over the other 2 but is it woth the extra 100$ for the 200,000PSI bolts over the 180,000PSI in a engine that will never see 6000RPM? I just ask seeing as forced induction adds stress on the bottomend. Is the 100$ worth the gain in reliability for this application?

Assuming the crank is damaged it's 150$ to have it turned. A Scat Forged Steel crank is under 300$. Should I consider purchasing a new crank for better durability and less down time waiting on the machine shop? Most of what I read here is people are pretty confident in the stock crank under 6000rpm and 600hp? Given the cost difference of 150$ is minimal what would yall suggest.
 
if you can get a 4340 forged crank, and use ARP main cap suds and you can afford to do so thats a great value, its not mandatory but you have no idea how many millions or revolutions that crank and rods have cycled through or how much stress they have seen, that existing cast crank is probably fine, but if your changing cranks Id select forged every time!
and yeah check the crank bearing clearances and crank journal alignment,
most better shops have the required equipment to verify crank saddle alignment, that MIGHT or might not change if you use ARP studs on the main caps.
716.jpg
 
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if you can get a 4340 forged crank, and use ARP main cap suds and you can afford to do so thats a great value

I apologise. Te crank I was referring to is, A Cast Steel crank. You have mentioned the Scat Cast Steel crank in many threads and it's priced under 300$ if I can find a Forged crank for a decent price I would not be against spending the money
 
for your application cast steel, is more than strong enough,
but if it was my engine Id go with a forged crank if I was swapping cranks simply because,
the existing crank is an unknown factor, and if I was forced to buy a crank,
Ive yet to see a properly built engine Ive built have a 4340 crank break,
Im certainly not suggesting it can,t happen, just that a forged crank is about 50% plus stronger!
as one of my LEO, friends says
: you don,t put on a bullet resistant vest because you intend too get shot,
its because you know the shit can unexpectedly hit the fan,
even if you do everything correctly!
and knowing you took the precautions you could,
prevents a great many bad things from happening!
 
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I would get all piston and rod assemblies out.
Inspect the skirts and ring grooves.
Copper from the tri metal bearings often will score the soft aluminum piston skirts.
If Ok then remove the rings on #1, #7, #2, & #8 pistons .
Reinstall.
Check the piston to deck heights at TDC each.
 
I am glad I signed up and reached out to this forum. I feel much more confident in tackleing the next task of correcting my inaccurate build. Im on duty starting tomorrow until Wednesday morning... so I will start tearing it down some time Wednesday. I will take photos as i go Thank you for the guidance thus far. Im proud to be a part of this place.
 
With the tear down we have.
1 crank that is mildly scored - needs turned
Cylinders are A-ok
Pistons look great.
Cam lobes and lifters are fine.

Deck height is 9.811

So with 6.535 rods we are .006 in the hole. With a .04 gasket I'm at .046 Piston to head clearance.

I have ordered:
Scat 2200A series H-beam rods
Scat Forged Standard Weight Crankshafts
Titan copper head gaskets @.040

I'm resizing photos at the moment. I will post them later.

My current cam specs with 1.7 ratio measured:
intake lift at cam .284 (.284*1.7)=.4828
Total exhaust lift of .282 (.282*1.7)=.4794
Duration at 209/209
Centerline is 110
LSA 115
Intake closes at 36
Spring pressure open is listed 238-262lbs


Is this a enough cam? The max lift for these heads are about .550 but that pushing it. Should I invest in a new camshaft looking at making power under 6000.

With the all Forged Internals would it be safe to push it up to around 5600-5800 wide open throttle? Vs the 5000-5400rpm I was shooting for when I started?
 
The cam was matched to the Supercharger.
Lots of testing done prior to production.

You want to use A cam factory or aftermarket designed for Boat Supercharger boost.
It's a Hot Air Style Blower charger.

Cam specs often appear tame.
They are.
Boost makes the engine come alive.
 
even the cast crank easily should handle the stress of 5800rpm, swap to forged and your adding about 50% greater strength.
 
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