   UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

        ANN ARBOR, MI 48105

January 12, 2007

                                                                        
                                        	      			                    
OFFICE OF 	                                                             
                                                                        
                       	               									             AIR AND
RADIATION

MEMORANDUM

SUBJECT:	General Motors Product Changes Affecting SD/I Engine Marinizers

FROM:	Mike Samulski, Assessment and Standards Division

TO:		Docket EPA-HQ-OAR-2004-0007

  SEQ CHAPTER \h \r 1 Gasoline sterndrive and inboard (SD/I) engines are
generally derived from land-based counterparts.  Engine marinizers
purchase automotive engine blocks to take advantage of cost savings
associated with economies of scale.  Marine engines are produced in
relatively small volumes compared to automotive engines and the
development of engine blocks by the marinizers would be expected to
significantly increase engine costs.  Marinizers prepare the engines for
marine use by   SEQ CHAPTER \h \r 1 adding the fuel and air management
system, marine cooling system, intake and exhaust manifolds, and
accessory drives and units.

	The vast majority of sterndrive and inboard (SD/I) marine engines are
based on automotive engine blocks produced by General Motors (GM).  GM
offers six engine blocks for marine use.  The smallest is a 4 cylinder
in-line engine with a total displacement of 3.0L.  This engine is
typically used for entry level boats.  The next largest engine is a V6
with a displacement of 4.3L.  This engine fills a niche in the marine
market in that it can typically fit in the same engine compartments as
the 3.0L engine but gives boaters a higher power option.  GM also offers
four different V8 engines:  5.0L, 5.7L, 6.0L, and 8.1L.  The 5.0L and
5.7L engines, which have been in production for decades, are the most
popular engines for SD/I applications.  The 6.0L and 8.1L engine blocks
are newer designs and offer higher power ratings.

	GM has recently announced that it intends to discontinue the 4.3L and
8.1L engine blocks in 2009.  The 4.3L engine is scheduled to go out of
production in May of 2009 and replaced with a 4.1L engine.  The 8.1L
engine is scheduled to go out of production in December of 2009 and
replaced with a supercharged version of the 6.0L engine.  Both of these
replacement engines are still under development.  GM’s projected
timelines for these engines are enclosed as Attachment 1.

	Attachment 2 presents information on the engine blocks used by the six
SD/I marinizers that are certified in California for exhaust emissions. 
These six manufacturers produce the vast majority of SD/I engines sold
in the United States.  In some cases, the marinizers change the length
of the stroke to provide a higher displacement option with a given
engine block.  This is represented in Attachment 2 by showing multiple
engine displacements for a company for a given engine block.  All six of
these companies will be impacted by the changes in the GM product
offerings.  Other SD/I manufacturers include airboat engine
manufacturers and high-performance SD/I engine manufacturers.  Many
airboat engines are based on GM engine blocks, though some are built
using aircraft engines.  High-performance SD/I engines are typically
based on custom racing blocks, though some smaller engines in this
category may use the 8.1L GM block.

	As shown in Attachment 1, marine engine marinizers can expect to have
access to prototype 4.1L and supercharged 6.0L engines in mid 2007. 
Marinizers have stated that they will need to design and build new
marine components for these engines, including exhaust manifolds, and
that they will need to develop new fuel system calibrations.  These
development efforts will likely include hardware and software designs,
performance and durability testing, and tooling upgrades.  As a result,
marinizers have raised concerns about having these engines ready to meet
emission standards in the 2009 model year.  Because of the engine
changes, it is unlikely that emission calibrations and catalyst
packaging developed for the 4.3L and 8.1L engines would be directly
transferable to the new engine designs.  Marinizers have also expressed
concern that they will not have enough remaining years of sales of the
4.3L and 8.1L engines to justify the cost of developing
catalyst-equipped exhaust manifolds for these engines.  

Attachment 1:  Projected Timelines for New GM Engine Blocks

Attachment 2:  Table of GM Engine Blocks Used By SD/I Manufacturers

 

Sources:

www.gmpowertrain.com

www.mercurymarine.com

www.volvo.com/volvopenta/

www.indmar.com

www.pleasurecraft.com

www.kemequipment.com

www.marinepowerusa.com

www.arb.ca.gov/msprog/offroad/cert/cert_mfr.php

 “SD/I Implementation,” presented to EPA by NMMA on October 26,
2006, Docket Identification EPA-HQ-OAR-2004-0008-0509. 

* Approximate number of engine power ratings is in parenthesis

4.3L block is planned to be replaced by a 4.1L block

8.1L block is planned to be replaced by a supercharged 6.0L block

8.1L

(4)

8.1L

(2)

8.1L, 8.2L

(2)

8.1L

(2)

8.1L

(2)

8.1L

(1)

6.0L, 6.3L

(2)

6.0L

(1)

6.0L

(2)

6.0L

(1)

5.7L, 6.2L

(8)

5.7L

(2)

5.7L

(2)

5.7L

(2)

5.7L

(2)

5.7L

(1)

5.0L

(2)

5.0L

(2)

5.0L

(1)

4.3L

(2)

4.3L

(2)

4.3L

(1)

3.0L

(1)

3.0L

(1)

Mercury

Volvo Penta

Indmar

PCM/Crusader

KEM

Marine Power

 

 

