AJ Enterprises
PO Box 276
Winter Harbor, ME 04693


E-mail us at <ajent@midmaine.com>

Alan Johnson -- Proprietor

Engine Choices
We can install just about any engine that an owner might like as long as it fits in the engine compartment. The new generation of diesel engines with computer controlled fuel injection and electronic controls offer fuel economy, lowered noise levels and less smoke and vibration. These are great steps forward in making these engines the best choice for use in small pleasure boats like our AJ-28. Most owners prefer the inherent safety of a diesel engine and that tips the decision in that direction instead of a gasoline engine. However we still offer gasoline engines and some owners still prefer these for a variety of reasons. The initial cost of installation of a gas engine is significantly less than a diesel, they do not have the diesel smell and are still the best at reducing noise and vibration to a minimum. The gas engine we use all have multi-port fuel injection and offer great fuel economy for gas engines. Our boats are easy moving and work very well with the gasoline engines available in todays market.

One note on the difference between Gas and Diesel engines is the cruise speed performance for each type of engine. Gasoline engines are lighter duty and it is recommended by the manufacturers that maximum cruise speed is 75% of WOT (Wide Open Throttle RPM). Most Chevy gas engines are rated at 4800 rpm and so the maximum continuous cruise rpm is approximately 3600rpm. The diesel engines are heavier duty and their cruise speeds are rated at 90% of WOT. For example the Volvo D-4 260hp engine is rated at 3500 WOT , and Max cruise speed would be 3,150rpm. This means that to get the same cruise speed you would need a gas engine rated about 20% higher than that of a diesel to get the same cruise speed.

The best Diesel engine choices for these boats are in the 150 to 350hp range. The 150hp engine should be considered the minimum and will give a cruise speed of around 16-18kts and a top speed of 20-22kts. A 350hp diesel will give a cruise speed capability of 28-30 kits and a top speed of 32-33kts these speeds are great as long as the sea conditions permit.

We have used the mostly Yanmar diesels in this range for years and they always give great performance in these boats. We have used the Volvo D-4 & D-6 engines and they are also great choices in these boats. We had a couple of owners who wanted to try the Steyr 4cylinder engines rated at 235hp and they worked well and had great fuel economy as reported by the owners.

As for the gasoline engines, we prefer to use the Marine Power Chevrolet conversions for these boats. They are of proven design and very installer friendly and that saves money for the owner during the installation. The newer 6.0L is right out of the new generation Chevrolet pickup and has had a great reputation there since 2000 and has worked out just as well in the boating world. If you are a traditionalist when it comes to gas engines you can still have a 350 or a 454 of the older generation “Chevy”.

One final word on the Gasoline vs Diesel decision. The fact that Diesel fuel is the safer of the two fuels is an absolute fact. Everyone understands that gasoline vapors can explode and nobody wants to take a chance on something like that. If for some reason your personal preference is a gas motor you can rest assured that we know how and will install these motors in compliance with all of the US Coast Guard regulations. We also follow all of the ABYC recommendations for installation and ventilation of gasoline engines.

The engines we prefer using right now are the Volvo D4 & D6 diesel, but again we can install any engine you might prefer.

To get a quote for us to install you favorite engine just call or e-mail us.





A January day in Winter Harbor Sometimes engines arrive in January
Speed and Fuel consumption Figures


(These figures are for average weight pleasure boats, and are actual GPS reading on actual boats)

ENGINE                        IDLE SPEED   /  CRUISE SPEED  /     TOP SPEED

Marine Power 350 Chevy  EFI 325hp       3.5 Kts         21.5 Kts         28.5 Kts

Marine Power 8.1L EFI Chevy 425hp       4.0 Kts         25.5 Kts         34.0 Kts

Yanmar 4 cly Diesel 240hp                       4.5 Knts        20.0 Kts         26.5 Kts

Yanmar 6 cyl Diesel  265hp                      4.0 Kts          21.0 Kts         27.0 Kts

Yanmar 6 cyl Diesel 320hp                       4.3 Kts          23.0 Kts         29.0 Kts

Yanmar 6 cyl Diesel 370 hp                      6.0 Kts          25.5 Kts.        32.0 Kts

Yanmar 6 cyl Diesel 440hp                       6.5 Kts          27.5 Kts         33.5 Kts


(Fuel consumption is more a factor of boat speed than engine  size. These are approximate figures.)

Most diesels will give the following fuel consumtion regardless of size:

16kts-4.5gph    20kts-6.0gph   24kts-9.0gph  28kts-15.0gph

Gasoline engines (multi-port fuel injected):

16kts-6.0gph   20kts-8.0gph   24kts-12.0gph   28kts-24.0gph   


Length Over All  -----  28’  6”                                     Cockpit length long top  ---  14’10”

Length at waterline --  27’  2”                                      Cockpit length short top  --   16’ 5”

Beam  -----------------  10’  4”                                       Head room helm station   --    6’ 5”

Draft  -----------------    2’  10                                        Headroom cuddy cabin  ----   5’ 8”