Many original engine marinser/boatbuilder alternator & charging setups are poor & outdated and can be improved significantly. Please scroll down to see the specific upgrades I offer for some of the most popular engines. Some of these setups I’ve developed myself and I’m really proud of – they’re not available or offered by anyone else. I only carryout the complete job and don’t supply parts as a kit.
With the popularity in fitting larger Lead Acid battery banks or Lithium batteries, having an alternator setup that can keep up with the increased demands is important. This page ties in with my work on Lithium systems as it’s often necessary to improve and modify an alternator charging system to take advantage of a lithium battery’s ability to quickly recharge, but have control so this same property won’t damage the alternator. Fitting an alternator controller is a great upgrade and things have moved on so much from the Adverc type system. The latest Mastervolt Alpha Pro gets the very best out of the alternator/engine setup but has features like a small engine mode to improve engine running and reduce belt loads & alternator temp sensing to protect the alternator. See my Matervolt Controller page or call for more details.
Installing a washing machine is a big deal converting a holiday boat into a proper liveaboard. It’s often necessary to improve alternator performance in order to keep up with a large inverter running a washing machine. I can complete the job from scratch – charging system, battery monitor, inverter and washing machine. It’s sometimes possible to fit a smaller 1300 watt Candy heater element to a washing machine to decrease loads on the inverter/charging system – please call for details.
Isuzu 200 Amp Bosch Alternator Upgrade.
The excellent Isuzu Canaline engines are let down by a particularly poor factory domestic charging setup. I have a 200 amp alternator upgrade running a freewheeling clutch pulley with a custom 6PK poly-v crank pulley conversion. This series of Bosch alternator is used in the £2k+ Mastervolt 14/200 package. Available for most of the 4 cylinder engines. Custom stainless steel adjusting arm and mounting bracket. A few options on alternator pulley sizes giving upto 4.2:1 pulley ratio. This upgrade transforms charging performance. Works very well with a Balmar MC-614 or Mastervolt Alpha Pro alternator controllers. Please call for details.
Barrus Shire Engines
**New** 200 amp Bosch alternator setup for some Barrus Shire 40 & 45’s. 6PK poly-v crank pulley conversion with freewheeling alternator pulley. Can replace the discontinued 110 amp Prestolite RDG5725. Custom folded stainless steel mounting bracket & adjusting arm. Unstrained & powerful, transforming the original setup. This kit isn’t suitable for all of the Barrus 40/45’s – call me for more details.
If you have a Barrus Shire 45/50 with the 240 amp Prestolite alternator you may experience poor charging performance due to the extremely low 14.0 to 14.20 voltage regulator set point, and also belt performance issues due to the 6PK belt setup which is unable to transfer anywhere near the 240 amp current through the solid alternator pulley. More info here.
For the ‘single belted’ Barrus Shire I have a 90 amp upgrade replacing the original poor performing Hitachi with optimistic 80 amp badge. Includes a custom 65mm pulley which gets the very most out of the XPA belt setup. I’ve done this conversion to well over 100 boats now.
Beta Marine Engines
It’s possible to replace the troublesome solid aluminium poly-V pulleys fitted to the travel power and domestic alternators on some Beta 38, BV1903, Beta 43 & Beta 50 engines. A smaller freewheeling pulley is available for the 95 Amp Iskra or this can be replaced with the 175 amp alternator as fitted to the later engines. I keep this in stock as a kit along with the custom Beta made freewheeling pulley and new belt. The poor performing 12 & 24 volt Delco Remy alternator can be replaced with a top quality Iskra 12V 175amp or 24V 120 amp. These engines can suffer from crank pulley issues which can potentially destroy the engine. This is a particular problem when charging big lead-acid and lithium with the large alternator loads they create. A Mastervolt Alpha Pro works so well here limiting loads at low engine speeds and increasing the load at the 1200rpm that Beta specify & looking after the expensive battery bank with it’s adjustable voltage and max charge rate.
Beta bv1505, Beta 35, Beta 38 90 amp alternator with small 65mm pulley, wider XPA belt upgrade and cable sizes uprated to 35mm. Transforms charging performance from the standard original setup:
For the later Beta 38 with 6PK crank pulley setup there’s a 200 amp Bosch upgrade available. A Mastervolt Alpha Pro must be installed to de-rate the alternator loads to suit the engine’s power at low speeds.
Engines Plus Canaline 42 12V 200amp Bosch Alternator Conversion.
For the 42HP engine with 6pk multi v crank pulley. Replaces the discontinued 110A Prestolite 35214420. Massive increase in performance throughout rev range. I use a custom alternator mounting bracket and adjusting arm, and fit a freewheeling alternator pulley which improves power transmission, helps stop belt squeal/chirping and makes for a smoother running engine. Can go down to a 50mm freewheeling pulley giving an excellent 4.2:1 pulley ratio. The photo shows a 175amp Mahle alternator and I’m now using a 200amp Bosch unit..
- As a guide rated alternator output in amps should be around 25% of a Lead Acid battery bank AH capacity. However this is a very general rule and other factors influence the recommended alternator size.
- Running a heavy load such as washing machine through an inverter will increase alternator demand greatly and is a key reason to improve alternator charging performance.
- Pulley ratios: a large engine crank pulley combined with a small alternator pulley increases alternator speed at given engine speed and this increases alternator output and alternator cooling.
- With V belts fitting a smaller alternator pulley decreases belt contact area. Also the shorter radius increases belt deformation and combined with larger loads puts more heat into the belt. When running smaller alternator pulleys It’s really important to use a good quality belt and IME Gates XPA Quadpower 4 are best. I have custom 65mm XPA pulleys available and this size generally gives a good compromise between alternator performance and belt (& pulley) life.
- Depending on belt wrap available, generally a 10mm wide AVX V belt can drive up to 70 amps. 12.5mm XPA up to 110 amps. Multi V flat belts can transfer significantly more power.
- It’s often possible to replace a 10mm wide belt with an 12.5mm wide XPA belt and fit an XPA alternator pulley enabling an increase in alternator size. The belt sits higher in the crank/water pump pulley and the only significant belt forces occur at the alternator pulley. This is relevant to some Vetus, Beta, Thornycroft, BMC & Ford engines.
- Poly V belts are pretty flat so don’t deform as much as a deep V belt running around a small radius alternator pulley. This means far less heat is put into the belt and they can reliably run around a much smaller alternator pulley – typically down to ~50mm.
- Poly V freewheeling clutch pulleys can transfer higher loads at a lower tension and run far smoother than the solid pulley version.
- Generally a modern alternator with dual internal fans and associated open casing/frame have far better cooling than a single external fan design – so can achieve higher loads for longer with better reliability.
- Fitting an external voltage regulator can greatly improve alternator performance and are particularly useful when charging better quality batteries.