3 Things To Consider When Choosing a Marine Generator There are two sources of critical power on your boat, your engine and your generator, or what we call your marine diesel genset.

There are two sources of critical power on your boat, your engine and your generator, or what we call your marine diesel genset. The engine moves the boat through the water. The genset powers every appliance – from the microwave, kettle and hot water system to desalinator and air-conditioner.

The genset you install must be able to run all of these with something to spare. So to work out the power you need, add up the wattage of all the appliances on-board. Then apply an extra 20% buffer for the additional start-up load. This will give you an approximate idea on how much power the vessel will draw, at maximum. To be 100% sure, speak to THT to confirm the correct size generator for your vessel.

1.     1500 or 3000rpm?

For 50Hz-rated generators, the two available options for engine operating rpm are: 1500rpm and 3000rpm.


These generators are fairly quiet anyway but when run through a water lock muffler, there is little to no external engine exhaust noise. They’re also designed to provide a longer service life and are great for commercial applications. The down side is that these marine diesel gensets are bulkier and heavier than a comparable 3000rpm genset.


Seems counter intuitive but 3000rpm marine diesel gensets are smaller, more compact units which makes them excellent for fitting into tight spaces. Due to the higher rpm, they do produce a bit more engine exhaust noise, producing a sound best described as a ‘low hum’ when run through a water lock muffler.

3000rpm units are perfect for recreational pleasure vessels where space is an issue.

2.     Single-phase or Three-phase?

Choosing between single-phase or three-phase power is dependent on what appliances are in your vessel and how much power they will draw. Most recreational vessels require only single-phase generators which are usually 3-25kVA.

Commercial vessels vary in their need for single or three-phase. If you have large water or hydraulic pumps on-board, chances are you will need three-phase power. Three-phase generators are mostly from 25kVA upwards.

3.     Open or soundproof – what will fit?

Marine diesel gensets are available in ‘open sets’ which means they have no cabinet. It makes sense then that ‘Soundproof sets’ are covered in to help keep the noise down. Being larger than open sets, and also slightly heavier, you need to measure where you want to put the soundproof generator to make sure it will fit.

Open sets are an advantage if you need to have good and easy access all the way around the generator – something a lot of commercial vessels prefer.

If quiet operation is a priority, soundproof sets are for you because they have powder coated aluminium or fibreglass covers all the way around, with sound attenuating panels inside. This does make them more expensive than open sets.

Also check to ensure that all the service points on the generator are accessible (including oil and fuel filters, sea water pump impellers, anodes and the oil sump pump). Make sure they’re not against a bulkhead so that the generator can be easily maintained.

THT Marine Sales Can Help You Choose The Right Marine Generator

Finding the right generator for your boat is all about some solid research. The biggest bank of knowledge you’ll find in Perth is right here at THT. We’re top gun marine diesel genset experts.

You can Contact Us or come straight in to Royal Street, Tuart Hill where our team has heaps of information to share just to get you on the water, faster.