Problems keeping stock OS outboard running.

[Jack Brady]

Hello, Last season we ran technology 55% fuel and had no problems. This season we were in a bulk order for red max fuels and we got 60% . I am running the last gallon of technology 55 and have no problems. My dads boat with the 60% red max wont go more than 4 or 5 laps and quits. Motor is barely warm. The only way we can keep it running is to run it real rich and very slow. We tried different fuel yanks and lines. We tried different engine that we know runs well and still the same. Finally we drained the tank and put in the technology fuel and it ran normally. Do you guys know anything with the red max fuel? Or if just 5% more nitro makes that much difference. We have a couple of cases of the red max and dont know what to do or what may be the problem with it. Thanks

 

[vision craft boats]

Hello, Last season we ran technology 55% fuel and had no problems. This season we were in a bulk order for red max fuels and we got 60% . I am running the last gallon of technology 55 and have no problems. My dads boat with the 60% red max wont go more than 4 or 5 laps and quits. Motor is barely warm. The only way we can keep it running is to run it real rich and very slow. We tried different fuel yanks and lines. We tried different engine that we know runs well and still the same. Finally we drained the tank and put in the technology fuel and it ran normally. Do you guys know anything with the red max fuel? Or if just 5% more nitro makes that much difference. We have a couple of cases of the red max and dont know what to do or what may be the problem with it. Thanks

Sounds like a bad batch of fuel. I run 60 year round down here in FL,most of us do.

 

[Duck899]

Sounds like water in the fuel or components in the fuel not right.....it happens.

 

[John Knight]

RedMax, unless it is a special order, generally uses 20% oil, 4% castor and 16% syn, for their boat fuels. This is what was done as recent as 2 years ago but I am not sure if they still do it. John Otto does not put this much % of oil (Morgan Cool Power oil) in his fuels unless asked for. And he uses all syn unless castor is asked for too. The RedMax oil is also heavier than the Morgan oil. Between the different % and the heavier oils in RedMax, that may be part of the problem. The heavier oil will not allow the engine to make internal heat as easy.

Try another fuel jug, new and unopened and see if it makes a difference. Also restrict some water to the water jacket to get the engine hotter. Is the head shim still in the engine? If so, take it out and run it without the shim. If these changes do not help, get in touch with RedMax and talk with a fuel engineer.

 

[Jack Brady]

Yeah, the head shim is out. How Hot is ideal? I am not talking exact temp but after a run and you touch the head should it be warm or pretty hot to the touch? Maybe like you say we are not getting enough heat in the motor.

 

[John Knight]

Yeah, the head shim is out. How Hot is ideal? I am not talking exact temp but after a run and you touch the head should it be warm or pretty hot to the touch? Maybe like you say we are not getting enough heat in the motor.

Jack,

The OB lowers act as a heat sink and draws heat away from the engine. More of a challenge for an OB than an IB. However, many of us use the 3 second rule. If you can keep your fingers on the head for 3 seconds or more, it is too cool. Others use an infrared temp gun (Radio Shack for about $30) and get the temp about 220 deg F. Bring the boat slowly back to the dock, beach, etc., and see what the temp is. If you bring it back and stop fast, you wash down the head and the temp reading will be false.

 

[HTV Boats]

Don't put too much stock in the heat left in an engine as it comes ashore. I have used the infrared temp guages and real time temp sensors on our outboards. Your peak temp will go down 10% or more just backing off throttle load. As it stops and settles into the water it rises slowly due to heat disapating out of the metal. Still nowhere near what you had running under load. To measure after the run accurately and consistently is near impossible in my opininion. Pay attention to how it runs while restricting water flow and see if it will run richer without falling off. More heat more fuel = more power. Tune to the rich side not the lean side especially on an OS.

Mic

 

[Jack Brady]

Thanks Guys. I am going to try to get more heat in the engine and also I am going to try a hotter plug. I am running a mc 9 now. We will se how it goes this weekend.

 

[Tony Newland]

In my experience more nitro = colder plug and a richer needle. +5% nitro isnt going to a huge jump though, I go back and forth with 50% and 70% several times per day testing things...... At least that always works nice on my boats.. In my OS XM I run Odonnell 89's with 50% Odonnell Fuel. Havent changed a plug in 2-3 weeks and never sucked an element.

Also the temp you get after a heat race right on shore is going to be very close to operation temps, heat just cant dissipate from the aluminum very much at all in the matter of 2-3 seconds, whatever difference there is, will be virtually un-detectable by anything other than an exergen temp gun (which in car racing is very common but for a guy to just have a gun in boating seems to be very rare from what I've seen this year)..... I keep mine around 200 and get mucho runtime out of my engines. Keep in mind water flow and mixture go hand in hand, if the engine is too lean no amount of water flow is going to cool it and vice/versa. Its a balance.

if your going through plugs having a hard time finding the needle, always go rich, rediculously rich. Go a turn out.... at least it will run and not overheat