Building the Glen-L HOT ROD - Transmission Page

Selecting an engine, transmission with the proper gear ratio and sizing the propeller for your custom built inboard can be a daunting task if this is your first inboard installation.   To help you sort it all out, we've listed specs and pricing for inline, down angle and v-drive marine transmissions as well as base marine engine and turnkey engine packages from several suppliers.   We've also included a gearing and propeller calculator and links to articles describing how to drill the propeller shaft hole.


Marine Transmissions

  • Co-axial (inline), Down-Angle and V-Drive models suitable for light pleasure craft use are listed.

  • In the Installation Drawing column, we've included links to Installation Drawings to help visualize the various engine/transmission combinations.  10, 12 and 15 propshaft angles are shown.

  • HP and RPM are Max Input ratings.  (G)=Gasoline & (D)=Diesel.  Click the hyperlinks to see the transmission specifications.

  • Pricing is for informational puposes only.  Prices highlighted in red indicate lowest cost supplier.

  • We've recently added Velvet Drive and Cyborg Performance transmissions.

Inline and Down-Angle transmissions
Manufacturer Model Mount
Angle Ratio Input HP @ RPM
G=Gas D=Diesel
Price Specs Installation
ZF 25 A Direct 8 Down Angle 1.5:1 209 @ 4800 (G)
165 @ 3800 (D)
$1519 Specs  
45 A Direct 8 Down Angle 1.256:1 303 @ 4800 (G)
240 @ 3800 (D)
45 C Direct Inline 1:1 357 @ 4800 (G)
238 @ 3200 (D)
63 A
Aluminum Case
Direct 8 Down Angle 1.215:1

97 lbs.
458 @ 4800 (G)
363 @ 3800 (D)
Max 502
Max RPM 5500
Inquire (1:56:1)
Specs Drawing +
63 C Direct Inline 1:1 458 @ 4800 (G)
363 @ 3800 (D)
PCM 80 I Direct Inline 1:1   $1770    
40 A Direct 9 Down Angle 1.23:1   $1720    
Velvet Drive 71 Series
Model 1017
Direct Inline 1:1

95 lbs.
360 @ 4500 (G)
Max 390

230 @ 4000 (D)
Max 300
Specs Drawing +
72 Series
Model 1018
Direct Inline 1:1

109 lbs.
550 @ 5000 (G)
Max 595

350 @ 4000 (D)
Max 450
$1099 (Rebuilt)
Specs Drawing +
72 Series
I/O Plug In
Model 1018-000-014
Direct I/O 1:1

150 lbs.
Liberty A Series
Model 3001
Direct 8 down angle 1.054:1 450 @ 4800 (G)
325 @ 3500 (D)
5000A Series Direct 8 down angle 1.05:1 450 @ 4800 (G)
340 @ 3500 (D)
$3495 Specs
Drawing +

Performance Transmissions
Manufacturer Model Mount
Angle Ratio
Input HP @ RPM
G=Gas D=Diesel
Price Specs Installation
Velvet Drive 72L
Liberty Series
High Performance
Model 3007
Aluminum Case
Direct Inline 1:1

76 lbs.
700 (G)
Max RPM 6000
Liberty Series
High Performance
Model 3011
Aluminum Case
Direct Inline 1:1

76 lbs.
860 (G)
Max RPM 6000
Liberty Series
High Performance
Model 3010
Aluminum Case
Dry Sump
Direct Inline 1:1

82 lbs.
Max 2500
Max RPM 6500
  Specs Drawing
Slow or fails to load
Liberty Series
High Performance
Model 3009
Aluminum Case
Dry Sump
Direct Inline 1:1

86 lbs.
Max 2500
Max RPM 6500
  Specs Drawing
Slow or fails to load

Performance Transmissions
Manufacturer Model Mount
Ratio Specs Price Supplier
Cyborg 900 Direct 1:1   $3399
1350 Dry Sump Direct 1:1 1350 HP, 1600 $3995
1500 Dry Sump Direct 1:1 1500 HP, 1770 $4175
Super Cyborg Dry Sump Direct 1:1 2000 $5299
Velvet Drive Mercury Quicksilver Stock and NEW Terminator series
modified Velvet Drive Transmissions.
Customer must supply 71 & 72 Series Transmission.

Stock 71C & 72C
Terminator 750
Terminator 950
Terminator 1200
Terminator 1350
Terminator 1500
CALL       Orillia, Ontario, Canada      
Cyborg, ZF & Velvet Drive performance transmissions BAM Marine


Manufacturer Model Mount
Angle Ratio Input HP @ RPM Price / Supplier Specs Installation
ZF 63 IV
(HSW 630 V1)
Direct 12 V-Drive 1.29, 1.56
2.0, 2.47:1
458 @ 4800 (G)
363 @ 3800 (D)
Specs Drawing *
85 IV
(HSW 800 V2)
Direct 12 V-Drive 1.644, 2.01
522 @ 3300 (G)
493 @ 3300 (D)
$5860 Specs  
220 V
(IRM 220 V-2)
Remote 10 V-Drive 1.23:1 562 @ 4500 (G)
400 @ 3200 (D)
$4861 Specs  
PCM Power Plus Direct V-Drive 1.48:1   $2567    
Velvet Drive 72 Series V-Drive Direct 15 V-Drive 1.21:1 500 @ 5200 (G) Gear : $7774
Chain : $8155
1.51:1   Gear : $7907
Chain : $8260
Gear : Inquire
Chain : Inquire
Liberty Series
5000 V
Direct 12 V-Drive 1.25:1 450 @ 5200 (G) $3684
$4695 simplicity-marine
Specs Drawing *
Casale Split Case
(Direct & In-out)
Remote 10 & 12 V-Drive Several
Unlimited Direct : $3335, In-Out : $3500

Inquire Casale Engineering
  Direct Drive

C500 Remote 12 V-Drive Overdrive
& Reduction
Heavy Duty
Call for price

Inquire Casale Engineering
Heavy Duty
Remote 12 V-Drive   Unlimited
Inquire Casale Engineering
Menkens   Remote V-Drive Several   Menkens V-Drive    


Supplier Links

See the links below for more models, details and pricing :


Installation heights

Installation heights from top of engine stringer
Dimensions taken from Installation Drawings @ 15 propeller shaft angle
  Velvet Drive
Riser Height ZF 63A
Down Angle
Liberty Series
Down Angle
Standard 25-3/16 24-1/8 25-5/16 24-9/16
3" 26-15/16 25-3/4 26-3/16 25-7/16
6" 29-15/16 28-3/4 27-3/4 28-5/16

Overall Keel to Riser heights (Standard Riser)
Dimensions taken from Installation Drawings @ 15 propeller shaft angle
Model Riser to Stringer Top Keel to Stringer Top Overall Height Overall Length Notes
ZF 63 A 25-3/16 6-9/16 31-3/4 42-1/16  
Liberty A 24-1/8 7-3/4 31-7/8 40-1/2  
71C 25-5/16 7-5/8 32-15/16 42-1/2  
72C 24-9/16 8-3/8 32-15/16 43-7/16  
350 MAG MPI with 71C         Drawing
350 MAG MPI with 72C         Drawing
350 MAG MPI with 5000A         Drawing
350 MAG MPI with ZF63A         Drawing
350 MAG Tow Sports with 71C 26-1/2 7-1/4 33-3/4 42-11/16 Drawing

Specs based on MerCruiser MIE 5.7 carbed version unless noted otherwise.


Turnkey engines and packages

In the following tables, we've selected several Turknkey and Partial engines from several manufacturers for comparison purposes.  Pricing is for informational puposes only.

Turnkey Engines and Packages
Description Supplier
MerCruiser Bobtail and engine/transmission packages   
MerCruiser, Indmar, Crusader & Barr/EDM Marine Engines
Engine & Repowering Guide
Crusader, MerCruiser and Volvo Penta Repowering Marine Engines
Marine Power, MerCruiser, Volvo Penta and Crusader Engine Packages
Crusader Engine and Transmission Packages Marine Engines (Holliston MA, USA)
PCM (Pleasure Craft Marine) Marine Engines
MerCruiser 350 Carb 71C Transmission / $8195    
MerCruiser 350 MAG MPI 71C Transmission / $8595    
GM 5.0L MPI 303 HP & PCM 1.23:1 Transmission / $9310    


Partial Engines
Description Induction Specs Model # Price Supplier
4.3L Vortec Marine Engine
SILVER Package
(1967-2011 Replacement)
Carb 225 HP @ 4800 4300-SS $3599 michiganmotorz Requires exhaust manifolds and related parts.
5.7 LH GM VORTEC POWER PAC Carb 300 HP @ 5000 Item # 1671 $4060 skidim Base engine, fuel and ignition systems, 8" harmonic balancer.
5.7L Vortec Power Pack Special
with Merc Exhaust
Carb 325 HP PPS350E $4295 dougrussell Includes exhaust manifolds and risers for Mercruiser application.
GM 355 Dressed Marine Engine Carb 365 HP / 390 FT LBS mbp3550ctc-marine $4995 blueprintengines Requires exhaust manifolds and related parts.    
5.7L Vortec Marine Engine
GOLD Package
(1967-2011 Replacement)
Carb 315 HP @ 5000 5700-IGOLD $5099 michiganmotorz Includes exhaust manifolds, risers, gaskets and bolts.
5.7L MPI Vortec
MPFI 330 HP @ 5000 5700-CrusaderSD $7499 michiganmotorz Plus shipping and taxes


GM Base Engines

May require intake manifold, thermostat, carburetor, flame arrester, fuel pump, ignition system, raw water pump, exhaust manifolds
Description Specs Model # Price Supplier
3.0L POWER PACK SPECIAL     $3599 dougrussell Includes carb, flywheel and distributor.
4.3L Vortec Base Marine Engine
(1996-2011 Replacement)
225 hp @ 4800
268 LB*FT @ 4000
4300-BaseV $2449 michiganmotorz Engine block, 4.3L Vortec cylinder heads, valve covers, marine oil pan, circulation pump, harmonic balancer, roller cam & roller lifters, roller rockers.
5.7L (350ci) Vortec Base Marine Engine
(1996-2011 Replacement)
295 hp @ 5000
355 LB*FT @ 3600
5700-BaseV $2699 michiganmotorz Engine block, 5.7L Vortec cylinder heads, center-bolt valve covers, 5-quart marine oil pan, circulation pump, harmonic balancer, roller cam & roller lifters.
Vortec 5700 (5.7L) Base Marine Engine 295 hp @ 5000
355 LB*FT @ 3600
Item # 1730 $3440 Engine block, cylinder heads, valve covers, aluminum 4V intake manifold with brass water jackets, circulation pump, oil pan, flywheel, harmonic balancer
Hardin Marine New GM Marine Base Engines    
H&H Marine Engine Service Ltd.
Vancouver, BC, Canada
Quest 3.0L GM Base $2,545.00 US    
Quest 4.3L GM Base $3,672.00 US    
Quest 5.7L GM Base $3951.00 USD     $ CAD    
BluePrint Engines (Marine Performance engines) Kearney, NE


Marine Conversion Parts
Part Description Part # Price Supplier
5.7L (350 ci) GM Delco Voyager EST Marine Electronic Distributor Kit (U.S Coast Guard Approved) GM Marine # 107-C $349.00   
Mounting Kit - Velvet Drive 71C & 72C transmission (mounts, oil cooler, hoses and plumbing fittings) Barr Marine # 494101 $346.00   



Shaft HP VS Speed : Gearing and propeller sizing calculator  Revised 07-FEB-2015

The SHP VS Speed Calculator determines optimum propeller diameter from HP and RPM using Crouch's Diameter-HP-RPM Formula. It will calculate attainable speed and propeller sizing for up to two engines with four transmission ratios per engine.  We've included an algorithm to calculate and plot minimum, average and maximum pitch ratio curves.  If the pitch ratio falls outside these curves, the shaft speed is unsuited to the boat and must be changed using either a different reduction gear and/or an engine of a different rated RPM.

We've run our calculator with the following data :

  • Engine Option 1 : 185 HP @ 4000 RPM, Engine Option 2 : 325 HP @ 5200 RPM
  • Displacement : 3200 lbs
  • Transmission Ratio : 0.88:1, 1:1, 1.25:1, 1.5:1
  • Required speed : 45 MPH

The spreadsheet is still under development, so if you find any glitches or have any questions about the spreadsheet, please send us an email.


PropCalcPlus : Gearing and propeller sizing calculator  Revised 15-APR-2013

Your transmission vendor should be able to suggest appropriate gearing and propeller sizing for your application. You can also do the calculations yourself with one of the many online propeller calculators.

Here's a quick explanation on how to select the correct propeller for your boat :

"The propeller is selected to load the engine and still permit full power to be developed. The propeller must allow the engine to come up to rated speed. It is incorrect to use a propeller so large that the engine will be overloaded, because this will not only reduce the power delivered to the propeller shaft, but more importantly it will cause abnormally high loading within the engine. This can result in destructive pressures and temperatures which cause premature bearing and valve failure. For ski towing, it is best to select a propeller which will permit the engine to maintain rated RPM when under load."

Source : Velvet Drive Installation Manual

Our downloadable Excel spreadsheet can help you select the proper gear ratio and propeller for your application.  We've expanded Surfbaud's Freeware Propeller Calculator for Excel to include a Theoretical Speed Table and Diameter-HP-RPM calculations.

You'll need to input several parameters into the spreadsheet, namely engine horsepower, Max RPM, gearbox ratio, displacement of vessel, waterline length and required maximum speed in knots :


Diameter-HP-RPM Formula

This Excel spreadsheet uses the Diameter-HP-RPM Formula from Dave Gerr's Propeller Handbook to find optimum propeller diameter from HP and RPM.

Click the image to the right for a PDF preview, or download the spreadsheet to do your calculations :


Calculate shaft angle from strut drop and transmission output flange location  Revised 12-APR-2013

Our latest calculator obviates the need to make a detailed shaft layout diagram to determine the shaft angle and shaft entry point for a given strut drop.

Definitions : Strut Drop and Shaft Angle

Photo courtesy of Glen-L Marine Designs

Drop is the distance from the strut base to the centerline of the shaft bore at the aft end of the strut.

Angle is the degree of the slope between the strut base and the shaft bore centerline.

Inputs required are limited to the distance from the transmission's output flange to the transom, keel to transmission output flange centerline and strut drop.  If you're stretching the hull, values may also be input to determine the shaft angle and shaft entry points for the stretched hull.

The sample calculator output depicted in the right hand side of this page was run with the following data :

  • Aft face of strut barrel to transom = 16"
  • Keel to trans output flange centerline = 4"
  • Strut drop = 7.5"
  • Alternate strut drop = 9"
  • Hull stretch factor = 10%

The computed shaft angle can be verified by using our Shaft Angle Table :

  1. Take the length dimension from the shaft entry point to the aft end of strut e.g. 28",
  2. Scroll down to 7.50" in the Drop column,
  3. Locate a value that is close to 28" in the Length column,
  4. The shaft angle for that length is listed in the Angle column.  Angle is between 14.5° and 15°.

The spreadsheet is still under development, so if you find any glitches in the spreadsheet, send us an email with the particulars and we'll look into it.


Shaft Angle Table  Revised 05-SEP-2017

Table computes the distance between the aft end of the strut bore and the shaft entry point for strut drops between 6 to 10 inches and shaft angles between 6 to 16 degrees.

Shaft Angle Table


Propeller Slip Calculator  Revised 20-APR-2013


Theoretical Speed Table

We have devloped a Theoretical Speed Table which calculates theoretical speed for various RPM, propeller pitch, reduction and overdrive ratios.

  • Given the desired engine RPM, the table presents multiple gear ratios, propeller pitches and resultant speeds.

  • Given the desired speed, engine RPM for multiple ratios and pitches can be determined.

Theoretical Speed Table


Shaft Angles & Layouts - Drilling the Shaft Hole

  1. Calculate shaft angle from strut drop and transmission output flange location

  2. Shaft Angle Table

    Table computes the distance between the aft end of the strut bore and the shaft entry point for strut drops between 6 to 10 inches and shaft angles between 6 to 16 degrees.

  3. Shaft Layout for Flywheel Forward Installation    

    Sample shaft layout for installing a flywheel forward V8 and Velvet Drive C71 transmission.

  4. Inboard Motor Installations Chapter 6 : V-drives     ( WebLetter 59

  5. Inboard Motor Installation Chapter 11 : Shaft Angles & Layouts     ( WebLetter 12

  6. Inboard Motor Installation Chapter 12 : Making the Shaft Hole     ( WebLetter 44

  7. Designer's Notebook: Drilling the Shaft Hole for an Inboard     ( WebLetter 119

  8. Riviera Shaft Hole Boring by Dave Lott, Glen-L Riviera builder (MS Word document)

  9. MerCruiser Inboards Installation Drawings     (

    These drawings may help you to visualize the various engine/transmission combinations.


Technical Articles

We've developed articles on the following topics :

  • Selecting the engine, gearing and propeller for your boat
  • Propeller Diameter Notes
  • Propeller Page
  • Inboard Installation Notes
  • Stretching the hull
  • Chevy LS1 Engine Conversion Notes
  • Parts required for inline installations
  • Frame Templates

Technical Articles


Flywheel Forward Engine Notes

We've developed a web page with some notes about Chris-Craft Flywheel Forward engines.

Flywheel Forward Page


LS1 Marine Conversion Notes

Links to marine conversion parts for Chevrolet's LS1 engine.

LS1 Marine Conversion Notes


Bellhousing and Adapters


Marine Engine Torque Vs. Marine Engine Horsepower


When it comes to engine horsepower versus engine torque in marine engine applications, most people make the common mistake of focusing on the marine engine horsepower rather than the marine engine torque. When it comes to both gas marine engines as well as marine diesel engines, in most cases focus should be directed to the torque more so than the horsepower. There is a common saying with in the OEM industry that "Horsepower sells a boat however Torque is what actually moves it". This could not be closer to the truth! One should realize that horsepower is really a measure of the torque over a given period of time. This taken into account by the rpm variable in the specification. The following equation may help to shed some light as well.

Torque = Hp x 5252 / Rpm (5252 is a constant)

It is interesting to note that the formula also verifies the typical torque bell curve when the torque trails off as rpm increases at the top end. One may consider that engines making torque at a lower rpm tend to work better in marine applications due to the fact that "most" boats tend to plane in the range of 2,000 - 3,000 rpm. It's not by chance that most marine engine manufacturers continue using the larger displacement - lower rpm, cast iron marine engines because of this fact. Many people wonder why these manufacturers haven't changed over to the high rpm engines the automotive industry has been converting to over the past 10 years; for the same reason the LT-5 Corvette engine and Lexus V8 engines didn't work very well in these marine applications --- nice Hp but at higher rpm's and therefore poorer low rpm torque characteristics.

Another interesting item to note is that since the proper method for propping a boat is to select the size prop that allows the engine to turn at it's maximum allowable rpm. It is required that a similar level of torque be produced at the top rpm condition as well as the proper planing rpm for a given boat hull (draw a straight line across the torque bell curve and see at what "lower rpm" this takes place. If this is not the case the selected prop will over-load the engine at the boats planing rpm and therefore yield very sluggish low rpm performance characteristics. For example a high revving engine that makes 400 hp at 5500 rpm would be making about 382 Lb-Ft torque (using the above formula) at 5500 rpm, since it would have a maximum torque output at probably 4,000 rpm it would be likely not to produce enough torque at 2500 rpm to make the boat plane very well since the prop was selected based on the 382 Lb-Ft value. Notice the higher the rpm an engine makes it's torque the worse this situation becomes.

In contrast to this; large engines that make significant horsepower at "very" low rpm's will therefore make a tremendous amount of torque, but at extremely low rpm. For example a diesel marine engine that makes 300 Hp at 2,000 is making 788 Lb-Ft at this same rpm. Noting that the torque curve is generated in "bell form", and therefore the maximum torque could be as high as 900 Lb-ft on this 300 Hp engine. Comparing this against a 300 Hp GM small V8 engine that makes 300 Hp at 5,000 and 375 Lb-Ft torque at 3200 rpm, this is a considerable difference. Very low rpm diesel engines typically make tremendous low rpm torque and therefore require specific gear ratios not supported by sterndrives, as well as requiring much larger diameter prop shaft's.

Source : Marine Engine Torque Vs. Marine Engine Horsepower (





  1. Hydrasearch Recreational Marine Hardware Catalog     ( Formerly Buck Algonquin Marine Hardware Catalog.

  2. Stright-Mackay Catalog     ( New Glasgow, Nova Scotia

  3. Mack Boring Marine & Industrial Accessories Catalog     (

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Building the Glen-L Hot Rod :      Revised 23-MAY-2018