GM Marine SB Compatible 355 c.i. Engine - 365 HP - Long Block
GM Marine SB Compatible 355 c.i. Engine - 365 HP - Long Block
GM Marine SB Compatible 355 c.i. Engine - 365 HP - Long Block

GM Marine SB Compatible 355 c.i. Engine - 365 HP - Long Block


GM Marine SB Compatible 355 c.i. Engine - 365 HP - Long Block


HP & Torque: 365 HP / 390 FT. LBS

Cylinder Heads: Cast Iron Vortec

Compression Ratio: 9.5:1

Camshaft: Flat Tappet - .480 Intake / .489 Exhaust Lift and 226 Intake / 236 Exhaust Duration @ .050 - 112° LSA

Pistons: Hypereutectic

Crankshaft: Steel Crank - 3.480" Stroke and 5.700" Rods

Regular price $5,899.00
  • Secure payments


  • HP & Torque: 365 HP / 390 FT LBS
  • Compression Ratio: 9.5:1
  • Cast Iron Heads
  • Flat Tappet Cam
  • Cast Steel Crank
  • Hypereutectic Pistons


  • Hand-picked seasoned block
  • Square and parallel decked
  • Align honed main bearing bore
  • Cylinders honed on computer controlled machine to within .0002 straightness and roundness
  • Cylinders are sonic tested for thickness
  • 4-Bolt Main
  • 4.000" Bored .040" over
  • 1-Piece Rear Main Seal
  • Mech fuel pump provision: Yes
  • Passenger Side Dipstick Drilled and tapped for clutch linkage

Rotating Assembly:

  • Cast steel crankshaft
  • 3.480" Stroke
  • OEM type 5.700" connecting rods
  • Hypereutectic pistons
  • Internal Front/ External Rear

Cylinder Heads:

  • GM Vortec cast iron cylinder heads
  • 1.25 dia. valve springs, hardened retainers and keepers
  • 2.02 swirl polished intake valves
  • 1.60 swirl polished exhaust valves
  • Elgin hardened push rods
  • Long slot rockers with positive lock adjusting nuts

Cam Specs:

  • Cam Type: Flat tappet
  • .480 Intake .489 Exhaust lift
  • 226 Intake / 236 Exhaust duration
  • @ .050 - 112 ° lobe separation angle

Ignition Timing:

  • 34 degrees total at 3500 RPM

Also Includes:

  • New cast iron marine intake
  • Valve covers
  • Oil pan


  • Replaces Standard Rotation engines only. Not available as reverse rotation.
  • BluePrint Engines recommends the use of a flame arrestor in marine applications and advises checking local laws to ensure compliance with the United States Coast Guard Requirements for Ignition Protection & Fire Resistance.

Engine Accessory Specifications

Your BluePrint engine was dyno tested with the parts and specifications listed below. If you prefer to install a different part, your engine may not produce the horsepower recorded on your dyno sheet.

Part Number: MBP3550CT

Fuel Delivery Type: Carbureted, 600 cfm *Not Included*

Spark Plug: Champion 13

Spark Plug Gap: .045"

Harmonic Balancer: No

Flexplate/Flywheel: No

Stall Converter: N/A

Intake Manifold: Marine, cast iron

Fuel Recommendation: 91 Octane

Timing (Initial/Total Advance): Initial timing - 10-16° and Total timing 32-34°

Firing Order: 1,8,4,3,6,5,7,2

Notes: Recommended break in oil for your BluePrint Crate Engine: BPP710, Not for EGR

Header Partners:  Click here for our Header Partners and recommendations.

Click here to download a copy of the Installation Guide that came with your BluePrint engine.


The satisfaction of our customers is our highest priority at BluePrint Engines. We use quality components to balance your engine's rotating assembly within two grams of spec. We dyno test your crate engine and certify that it's ready to deliver horsepower and torque.

We give your BluePrint engine the industry's best-in-class warranty for 30-months / 50,000 miles — with the extra confidence only BluePrint can provide. Our warranty applies to individual or professional installations and is fully transferable.

For a detailed overview of our warranty, click here.


We make sure we hit our target horsepower and proper torque with every crate engine. We use an advanced computerized balancer to get our rotating assemblies within two grams, ensuring silky smooth power over the entire RPM range. That's precisely why our engines sound and run better than our competitors.


A comprehensive, dyno-generated printout showing these critical specs will accompany your delivered engine. No more guessing or wondering what your installed engine's real-world peak horsepower and torque ratings actually are. Any doubters in the crowd? Simply flash 'em your dyno results!

This engine will be dyno tested before it ships to you at no additional charge (others charge $500)!

Harmonic Balancer - GM SB Compatible - Internally Balanced
BluePrint Engines Crate Engine Break-In Oil — 1 Quart
BluePrint Engines 10w30 Engine Oil - 1 Quart
GM SB and BB Compatible Oil Filter
8mm Spark Plug Wire Set - 90° Boots - GM SB Compatible
Liquid Filled Fuel Pressure Gauge - 0-15 psi