Long Island Marine Surveyor

Telephone 631 589-6154  Fax 631 563-3758

 NFPA USSA  FMANA SNAME USNI ABYC 

Long Island Marine Surveyor 631-589-6154

Long Island Marine Surveyor

Boat Engines

Boat engines are of one of the following designs:

Gasoline or Diesel, fresh water cooled or raw water cooled, outboard or inboard.  

Gasoline engines are generally less expensive that diesel engine.  Gasoline engines can be either fresh water or raw water cooler and can either be outboard or inboard engines.  Outboard engines are generally two stroke engines as compared with inboard gasoline engines which are four stroke.  Some new outboard engines are now four stroke engine and are being well received in the outboard engine market.

Diesel engines are also raw or fresh water cooled.  They are more expensive than gasoline engines and are considered safer.  A diesel engine will weigh much more that a gasoline engine of the same horsepower.  While gasoline engines need a spark to ignite gasoline, diesel engine ignite fuel by compression.  Diesel fuel will not ignite by a spark, while gasoline has a flashpoint of -45 degrees (below zero), diesel fuel has a flashpoint of 125 degrees.  This means that at 45 below zero gasoline will give off enough vapors to ignite while diesel fuel will not produce enough to ignite until it reaches the temperature of 125 degrees.  The much higher flashpoint of diesel fuel makes it a much safer fuel to use in boats.  A diesel engine will last much longer than a gasoline engine when properly cared for.

Raw water cooled engine tend to have a much shorter lifespan when the raw water cooling them is salt water.  Raw water cooled engines that are used in fresh water like lakes have a much longer lifespan.  Salt water will corrode an engine from the interior.  A salt water cooled gasoline engine has a life span of about 10 years maybe less depending on maintenance and use.   All outboard engines are raw water cooled.  All diesel engine are freshwater (coolant) cooled.

Fresh water cooled engines are engine that have a cooling system using a heat exchanger.  Fresh water cooled engine will last much longer than salt water cooled engines.  A fresh water engine has antifreeze which circulates in the engine, the antifreeze is cooled by salt water in a heat exchanger.  Salt water enters the heat exchanger cooling the antifreeze the antifreeze then cools the engine.  The correct mixture is 1/2 antifreeze and 1/2 water which produces what is referred to as engine coolant.  This system will extend the life of the engine but must work correctly or overheating problems will occur.  Overheating will seriously damage and engine.  Inspection of the system includes pressure testing the cooling system if needed.  Pressure testing this system will insure not leakage exists in the coolant system.  A gauge is placed onto the heat exchanger and the system is pressurized to 15 psi.  Internal leakage in the engine from the head gaskets can be determined with this pressure check.

The engine is the heart of any boat.  An improperly working engine will cause nothing but problems.  Replacement of a gasoline outboard engine will run anywhere from $3,000 for a smaller boat to $10,000 for a larger boat.  A inboard gasoline engine replacement will cost from $7,000 to $10,000 for the average boat. Diesel engine will cost approximately $5,000 for a sailboat to $30,000 for a powerboat.

A boat engine should be compression tested if any problems are apparent or suspected.  (See compression testing of engines).

Inboard Boat engines are essentially auto engines that have been modified for boats.  These engines have been produced for years by the auto industry and do perform very well in boats and cars.  The problem is that these engines are made for cars.  Cars have a transmission that down shifts an engine so that it is mostly running below 2000 RPM.  Boats do not have transmissions that down shift.  When a boat needs to go faster it must increase its RPM.  Boat engine normally run at 3500 RPM and higher depending on the vessels speed.  When an engine runs twice as hard as it was meant to twice as many problems will developed.  Boat engines are run for about 50 to 150 hours per season.  You probably put 150 hours on you car engine in two weeks of driving.

Engines have starters and alternators (except for small outboards).  These are electrical items and when subjected to a salt water environment can cause problems.  Inspection of alternators and starters are part of a marine survey.  Starters and Alternators of marine gasoline engine should be explosion proof.  Explosion proof equipment is that which has the USCG approval J1527.   Spark arrestors are present that prevent these items from ignite an explosive atmosphere.   All electrical equipment attached and capable of producing a spark must be explosion proof equipment as per ABYC and USCG standards and regulations.  Since we have auto engines automotive alternators and automotive starters will fit.  Many home mechanics have replaced marine alternators and starters with automotive equipment only to have their boat blow up.  Please do not ever do this.  Please make sure that any boat you buy does not have automotive starters or alternators. J1527 must be on all approved USCG electrical equipment on engines and in engine compartments.

(See NFPA, USCG and ABYC directives and recommendations for more specific information).

Rust and corrosion are major problems for salt water operated engines both diesel, gasoline, raw and freshwater cooled, inboard and outboard.  A large percentage of problems arise from rust and corrosion.  While engine are often painted to maintain a good cosmetic appearance, especially when a boat is for sale.  A rusty old engine is usually just that and should be avoided or at least closely inspected.

Engine should not be leaking oil.  Oil in the bilge indicates problems.  Rusty oil pans or poor oil pan gaskets will leak oil into the bilge and are not cheaply repaired nor are they easily found.  Replacement of a poor oil pan gasket usually involves raising the engine from the boat.  Alternator belts should be tight.  Water pumps and their impellers must be replaced yearly.  Oil coolers inspected.  Strainers should be in place to prevent the engine from picking up sea weed, eel grass and other items that will prevent water from cooling the engine.  My recommendation is for professional maintenance of engines a qualified mechanic is worth his weight in gold (during August anyway).

Engine wiring should be neat, clean and color coded.   Spark plugs and wires should be changed yearly.  All engine gauges must be properly working especially oil pressure and engine temperature gauges.

Key Benefits of a survey

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