Isuzu Marine Diesel

[clarity36]

Perchance generated interest from members re Isuzu diesels; I am seriously looking at a marinised Isuzu as a repower for Clarity. Would members have an opinion of 3 cylinders versus 4? My options are the 3CD1, rated at 35.5hp (3000rpm) or the 4LC1 rated at 38hp (3000rpm). 3 cylinder vibration versus the increased complexity of 4 cylinders? An authority? advises me that an odd number of cylinders in a diesel is a more efficient engine. Any feedback would be appreciated. Thanks. Bill

[GordMay]

Originally Posted by clarity36

... An authority? advises me that an odd number of cylinders in a diesel is a more efficient engine. Any feedback would be appreciated. Thanks. Bill

I'll be interested to learn what our expert mechanics think of that opinion, and why.

[anjou]

A 5 cyl block has always been popular for john deere and case, but an auto motive 3 cyl doesnt gain any advantage.

Where is the power curve at the typical operating revs of 2,200 - 2,500 rpm?

Does the isusu have an alloy or cast steel head?

[Ram]

I have a Isuzu 6DB1 mariniesed Diesel engine, in my Albin Trawler, I have 2300 hrs on it, used it as a commercial dive boat for about 10 years off Palm Beach, in that time I did nothing but change oil/filter and put fuel in it and it cranks first crank--every time- about 7 years ago i put it on the hard and have not started it for about 4-5 years- I left it on a rental proprity I own and one of the tennets have vandalized the boat- took a hammer and broke all the gages , compess and filled the boat with garbage ect, the guy was mad because i was evecting him for not paying the rent- -Now im getting ready to put the boat back in service and am wondering if this guy put a water hose in the engine,that would be the way to really screw it up- if he did not I would expect this engine to start up right away-I will know in a few days- I poured a quart of Marvel oil down its throat a year ago and am crossing my fingers- Anyone know where I can get gages for this engine? and shop manuel?

[never monday]

Originally Posted by GordMay

I'll be interested to learn what our expert mechanics think of that opinion, and why.

A 3 cyl will be more smooth than a 2 or 4 cyl. The pistons on most are at 120* intervals of crankshaft rotation. A 2cyl has the pistons in 180* opposing each other. A 4cyl has 2 pair of pistons 180* opposed. .

[doug86]

Originally Posted by clarity36

). 3 cylinder vibration versus the increased complexity of 4 cylinders? An authority? advises me that an odd number of cylinders in a diesel is a more efficient engine. Any feedback would be appreciated. Thanks. Bill

the 3 should be slightly more balanced, but the 4 will develop more torque. I don't think there is much increase in 'complexity' adding just one more cylinder; if the engineering is sound for 3, it would be identical for 4, no?

Properly mounted and underway, I think you would be hard pressed to notice any vibration difference between those two engines.

I had a 60hp Isuzu that was marinized by Pisces. It ran flawlessly, and I was told that the basic engine is used world wide as a forklift motor, which meant that the non-marinized parts were available on 5 continents. I never had a chance to prove that right or wrong because I never had to buy any parts for it.

Doug

[Laidback]

I recently installed another professionally marinized 67 Hp Isuzu - the 4JB1 model engine - naturally aspirated
- This is the 3rd of a number of Isuzus chosen to replace : Ford, Perkins, Volvo and Yanmar.

The member Ram who is restarting a vandalized engine might consider first checking the dipstick for water, if water is seen drain the engine oil, if water is found then consider disconnecting the injectors, then cranking that engine - checking to see what is pumped out, if water is observed then it will be necessary to drain the engine's oil again , change the oil filter and resume cranking before starting the engine.

Toyota produced a 5 cylinder diesel engine for export pickups, whilst proved to be well balanced engines and ran very well, but for some non technical reason they were discontinued.

[klem]

I can't see any reason why an odd number of cylinders is more efficient than an even number. The number of cylinders is important but it does not have to do with odd or even provided that the engine is properly balanced.

The energy in the fuel is converted into three forms in the engine, useful work, heat into the block, and heat into the exhaust. The goal is obviously to make the useful work the highest percentage of this total possible. Changing the heat out the exhaust is possible but really comes down to a well designed combustion process in the cylinder. However, it is possible to change the heat that is lost to the block. The important ratio here is surface area of cylinder/volume of cylinder. The larger the cylinder is, the lower this ratio is meaning that the engine is more efficient. For a given displacement, the only way to get a larger cylinder is to decrease the number of them. This is a major reason why large diesels such as those in ships can achieve over 50% efficiency. However, this extra efficiency can only be realized if the combustion process in the cylinder is optimal which requires adequate airflow, fuel atomization, etc.

Changing the number of cylinders also needs to affect the bore or stroke or both. This will mean that the engine has different hp, torque, and rpm characteristics and has some efficiency effects as well.

While I do not have much experience with Isuzu engines, all of it has been quite good.

[Searles]

Most large marine oil engines are odd number of cylinders ,have seen straight 11 and13 cylinder 2 stroke engines up to about 50khp the four stroke are more often even number cylinders ,my own work boat 36ft 13tns has a 1953 five LW Gardner,over60k hrs sweet as a nut ,wot 1500 rpm lots and lots of odd number cylinder engine’s because they balance better

[Compass790]

Originally Posted by never monday

A 3 cyl will be more smooth than a 2 or 4 cyl. The pistons on most are at 120* intervals of crankshaft rotation. A 2cyl has the pistons in 180* opposing each other. A 4cyl has 2 pair of pistons 180* opposed. .

+1 for this comment