Honda GX-50 Outboards

Greetings, since many of you seem to love acronyms…I created AMLIT…American Living In Thailand.
An ME, former oil refiner, former motorcycle road racer and car racer. I am a sensor tech geek and a control systems designer. Yes, an ME, plus much process and electronics experience. I have some Honda experience here, with former HRC and AP Honda gurus.
We run an API Tech ECU, with Blue-tooth to phone or laptop tuning. The phone tuning is quite fun on the road! It isn’t always working. The tuner good, the ECU has glitches. My main man has health issues, so working that and not ECU’s.

My purposed design plan for the future Nano is smaller engines. We have designed, and soon building small, inexpensive outboard engines for racing, fishing, water taxi’s on the canals here. The engines will be Honda GX50 or bigger, all made right here.

The outdrive is a modified existing design, but our own. We are building them as surface drive units to further efficiency. (Prop begins submerged, then we lift it to near 50% exposed) Carbon fiber use in the right places.

Our current prototype only weighs 5.4 kg. (12 lbs.) We have tested near 3.0 HP. The fuel consumption is good already, but surely we can optimize performance and economy with a tiny EFI. Run them at any temperature, humidity and altitude with near equal capability.

That is our new goal. Honda, Nano powered outboard and kart engines. Ohhh, and rice equipment…sound crazy? The small rice farmers use diesel engine tiller rigs, soon to be curtailed. HP Honda’s to the rescue!

Very cool. Do you happen to know the charging/electrical capacity of the GX50? Particularly how many amps @ 12v the charging system can produce at idle.

What kind of glitches are you encountering with the API Tech ECU?

The GX50, GX100 do not have a charging coil. They are magneto pickup ignitions. The GX120 and above do have charge coils. We have a 12 V linear actuator for adjusting our prop depth, so we run a lithium 12V battery with a solar panel. Works so well, that we have never had to do anything. I think a simple lead/acid 7ah battery would work.

The glitches in the API Tech are a bit confusing. Sometimes it just shuts down. I think it is a heat issue, but that means…capacitor? Not sure. I relocated nearly everything in my project bike…fuel tank is under the seat, air box is where the tank cover is…battery just behind. The ignition is OEM location, right side near the radiator overflow tank.

Sadly, the owner/tech brain had a stroke and is back in Japan…not doing well. The locals are good at the dyno work and analysis, but short on advanced design. The unit has no heat sink. It is a sealed black box. My colleagues in the Philipines do not have that issue. All built here, I think. Maybe mine has an internal issue.

I am not married to the APITech….but need to move on. We are going to do a Bangkok to Nepal trip and need reliable ECU. I am currently using a unit for a CBR300R on my CRF250L. The mapping is good, but cannot modify. Effectively, I have a 250cc with EFI and cams and air box for a 286cc CBR. (CBR300R) Same engine, different bore, different exhaust.

Very interesting use of solar. If the system has an additional 50w to 60w output capacity, you should be good for injection. I believe a 7aH battery should be a sufficient reserve, depending on how long you might encounter low-sunlight conditions on any given trip.

If the issue due to heat, then it’s more likely related to an internal power regulator. Many regulator IC’s feature a thermal shutdown mode that will cut power temporarily to protect itself from burning up.

I am thinking a few options, Travis. Though the smaller engines do not have charging coils, I might be able to adapt a charge coil. The GX 120 cc has 25 and 50 watt coil options. I would have to check fit. However, if I knew peak Nano consumption, I can easily get a lithium battery that is worthy, and solar combo. Our boats will have solar regardless…and two batteries. One for a linear actuator, (and engine?) one for the other console needs. The linear actuator is simply for trim.

Update on this, related to the CRF. Thank you for the info on thermal regulator IC shutdown. My mounting is in the OEM location, but the Honda PCM/ECU had a small heat sink…the API does not and is in dead air near coolant return. It does get hot after engine shutdown and when driving in traffic. No highway issues.

I think all I would need here is to build a throttle with injector inlet for the Honda GX series. I saw some GY6 ones. Quite massive and would need machining…from 28mm down to whatever…for the 50cc maybe only 20mm venturi. If the Nano kit comes with all else? Good to go!
I have baseline maps for the CRF in 250cc stock, plus cams and head flows and a few pipe dumps… the 286cc the same. But no base line for a GX50/100/120/160, where my real interest is. No real flow bench. Old school methods, not exact.

I believe you can expect approximately 50w - 60w of draw from the pump, ECU and injector depending on your exact setup. So adding a charging coil to the engine may not be necessary if your solar setup already has at least 60w unused capacity. Also, there may be better options for a smaller pump that could reduce the power requirements significantly. The pump is the hog.

It may be easier to work out a method of mounting a TPS sensor to your stock carburetor’s butterfly, and run it dry to act as your TB. Then add in a spacer/plate behind the carb to mount in the injector and a TMAP sensor. I’ve had good success with this kind of setup in earlier testing.

We’ll have at least a basic form of O2-based self-tuning in BETA, should be helpful for establishing a baseline for those GX’s on the dyno.

I’m excited to see what you’ll do with this, and how Nano can improve on things versus API. Do you have any pics or videos of the existing GX50-powered craft? If so, feel free to post them. I’ll check it out :+1:

Just an update Travis and all. Here in Thailand, things are showing signs of a return to business. To date? Food and health care. We have, however, used your questions to look into the tiny 50cc to assist in power generation to go along with our solar. The pump has a vacuum assisted “lift pump”, which helps a bit with any injection system pump. A bit? hmmm, positive pressure to the electric pump suction.

We are currently using either a lithium ion or a gel cell for pumps and gauge needs. I am not concerned about the power required. We can make it. We might be designing/adapting our own alternator, if truly needed. Easy to use the clutch drive. (alternator fits below the clutch bell.) If we use engine rpm, we can near-max output quite easy. (3800+/-)

Ohhh, an addendum to the above. For those who might not be this involved: A typical alternator on a car or motorbike, reaches max output in the 4500 to 4800 rpm range. So, if your alternator puts up 14+ volts at 4750, as an example…above the needed volt s required, it would either be shunted or stored.
So, for Nano EFI purposes, please understand that your system need only meet the requirements of the Nano controller, the pump and whatever you desire to display in gauges. That can be quite big or not.
We separate the needs. Need to have a robust controller? (Nano) one system. Need to have a starter and fuel pump? Another battery system Gauges and goofy fluff? Maybe another.
WE use an “engine system”, with two small cells that exceed needs. The gauges and pump? By itself, with solar backup, plus…we are doing a “oh shit” system from the engine. Trickle, if needed. No issues with conventional engines…our 50cc Hondas? less problems.