NexGen 3.5 KW Generator upgrade in 30 Pilot II

[rgano]

The Nexgen 3.5 in my boat, like just about everything else, was installed before the danged deck mold was added with no regard for eventual maintenance. So, when the crappy 12-volt Jabsco cooling fan for the electrical end quit recently (engine hours about 200) causing the wiring to it to burn up and fill the boat with smoke (because some fool never placed a fuse in the circuit), I was faced with having to remove the generator from the engine compartment in order to remove and replace the fan as well as its aged and holed plastic duct hose. I had to cut the exhaust hose and seawater hoses going to the siphon block because I could not gain enough access to their hose clamps. These were upgraded to better material and lengthened upon re-installation to allow generator removal in the future.

While others with this generator have told me it runs fine with the fan off, Nexgen says it will shutdown under a load without the fan running due to thermal overload. I am not interested in challenging what the manufacturer says, nor do I want to damage the long term health of the generator due to consistent overheating. I am, however, interested in NEVER having to replace the fan again.

The biggest part of the upgrade concerned changing the cooling fan from 12 VDC to 120 VAC, something that Nexgen told me would be a more dependable feature. Their reason for not doing this was the added complexity of a 120-VAC fan. The generator has no 12-Volt windings; so the battery charger needs to be run to prevent the fuel pump and fan from running the battery down over time. The fan is clearing a lot bigger load than the itty bitty fuel pump, and thus the battery charger can be run at a lower power factor or not at all.

Concern over possible improper voltages hitting the 120-VAC fan's motor during generator startup, lead me to investigate two options to start the fan after the generator had reached stable a running condition; running wiring to and installing a separate switch at the main power panel or installing a time delay relay back at the generator. I chose a time delay set to 30 seconds. With no room in the generator's sound shield, I chose to mount the relay on a small shelf I made out of formed plexiglass on the engine compartment aft bulkhead.

New fan is a Vents VK 100 fan rated at 162 CFM. Nexgen said to get a fan rated at 165 CFM to 250 CFM, but even the Jabsco 12-Volt POS was not rated for much more than 100 CF.

Time delay relay is a Schneider Electric model TDRSOXP-120V.

The old holed and cracked plastic hose air duct was replaced with aluminized flexible dryer duct.

Total cost of parts around $450, including $200 for new wiring harness and $100 for fan. Labor, including the two friend who helped me lift the generator out of and back into the engine compartment - ZERO.

 

[jskinner30PII]

Rich,
Thanks for posting. I figured I need to pull the entire unit just to replace that belt on the back side. I can't even reach the outboard rubber strap for the casing / cover. Now I have something else to look at? Do you have a picture of the placement of your unit? Is it starboard of the shaft against the rear bulkhead?

 

[rgano]

Yes, the unit is stbd against the aft bulkhead and is only held in place by two screws though the fwd two aluminum straps running under the fiberglass tray of the sound shield. I have to lie on the cockpit deck with my upper body down over the generator and then awkwardly reach around the outboard (stbd) end of the generator in order to reach the rubber clip which hold the aft piece of the shield to the fwd stbd piece. However, removing this fwd stbd piece of shield does little good because there is still little to no access to anything except maybe the air filter, AND you still must move the whole generator around a bit to be able to get the large aft piece of the shield off to access the main drive belt. I doubt the exhaust hose will grant you enough leeway to accomplish this. I added a 45-degree fiberglass elbow and about a foot of exhaust hose to be able to have enough slack in the hose to accomplish this kind of activity. I also changed out the two hard hoses goin to the anti-siphon valve to longer softer silicone hose to make sliding the generator to port enough to be able to access the three hoses.

If you are removing the generator for ANY reason, I heartily recommend getting rid of the crappy plastic vent hose pieces and the even crappier Jabsco 12-volt fan. I have lost count of how many of these fans I have had to replace in this and my previous boat. It was never intended for this kind of service. There are some quality 12-volt fans, but you will pay a couple hundred dollars for them, and you are still stuck with having to run the battery charger to prevent draining the battery over time.

The 120-volt fan I used was bigger than the Jabsco and had to be held in place with some giant zip ties back up in the alcove created by the deck mold where the step is at the aft stbd side of the cabin.

Fitting the new duct hose was a bit of a challenge because the exhaust fitting on the stbd side of the hull is some goofy small side, well under three inches in diameter while the typical in-line fan of sufficient capacity has four-inch openings, and the fitting on the generator's exhaust ort on the sound shield is 3 inches in diameter.

The solution was to buy two 3-to-4 inch plastic duct adapters; fasten one end of each of the two 4-inch dryer duct hoses to them with hose clamps; use 5200 to glue one of these adapters to the inside of the hull over the short tube sticking in from the hull exterior fitting propping in place and allowing to dry for two days (LONG arms needed); remove the exhaust flange fitting from the generator's sound shield and stick the other adapter in there with some vinyl tape used to enlarge it a tiny bit to make a snug fitting. The free ends of these two hose sections were of course clamped to the fan before I backed my aching 69-year old body out off the generator shelf.

This was a week's worth of off and on work in the Florida summer heat and humidity, but I firmly believe the upgrade will result in a much more reliable and maintainable unit where I won't have to climb over the rails onto my brother's 42-foot Grand Banks in a remote anchorage in the middle of the night for an air-conditioned bed because my stupid fan burned up and filled my boat's cabin and engine room with smoke leaving me no AC.