Long Island Marine Surveyor

Telephone 631 589-6154  Fax 631 589 0084


Long Island Marine Surveyor 631-589-6154

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Long Island Marine Surveyor

Boat Size Power or Sail Boat Gasoline or Diesel Engine Boats Inboard Outboard or I/O Fresh or Raw Water Cooling System Boat Style Boat Manufactures Used Boats For Sale Boat Appraisals Boat Brokers or Dealers Boat Sellers Responsibilities Boat Buyers Responsibilities Contacting a Marine Surveyor Marine Surveyors Fees



Outboard Engines, Inboard Engines or Inboard/Outboard engines.

An outboard engine in bolted onto the transom of a vessel. Of the three types of engines listed above it is the lightest. Outboard engines are somewhat less expensive than inboard or I/O engines. They are easier to replaced and can be lifted out of the water when not in use. The older outboards are two stroke, some of the new ones are four stroke engines. Four stroke is better. Outboard engines are only designed for boats while most inboard engines were designed for cars and adapted to boats. 

On the average I have found that outboards do not last as long as inboard engines. While I know someone reading this has an outboard that is 40 years old used regularly and runs like new, most outboard last about 750 hours before needing a major overhaul like a new power head. Inboard gasoline engines last about 1500 hours. Inboard diesels 3000+ hours.  


When you turn the boat to port or starboard the entire outboard engine moves. It is this movement of the engine that makes steering the vessel easier especially when maneuvering in reverse. This maneuverability when the vessel is placed in reverse is shared with stern drive boats but not inboard boats, which use a rudder for steering.


The major different between an I/O boat and an inboard is the transmission or gear. In an inboard boat the gear is inside the boat and on a I/O the gear or transmission, also called a stern drive unit is mounted to the transom on the outside of the boat. The stern drive unit is sometimes referred to as an out drive unit. This out drive or stern drive is almost always submerged in water. Well being always submerged in water reduces its life expectancy. A stern drive unit or out drive on an I/O boat will generally last 750 hours. While an inboard transmission or gear will last 3000 hours before needing a major overhaul. These are not inexpensive units, a stern drive can cost $5000 or more to replace.

Inboard boats that do not have stern drive units can have one of two types of transmissions or gears, a straight drive transmission or a V drive transmission. Both of these transmissions are inside the vessel. The straight drive transmission will give about 3000 hours of service before needing a major overhaul and the V drive transmission about 1500 hours of service. More stress is placed on the V drive .transmission since the drive shaft forms a 45 degree angle with the engine. The benefits of a V drive are interior cabin space. A V drive allows the engines to be set back further aft midship giving more interior cabin space.

A major benefit to inboard engines and inboard transmissions it that they are generally inside the boat away for the elements. This extends the life when compared to transmissions or engines that are subject to the elements.  Outboard and I/O are submerged.

Please contact us directly at neboaters@aol.com we would be happy to assist you in answering any questions that you may have.


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