loosing power on take off on hot days

[jopes]

This happened a couple time last year on hot days. Take off and the engine starves for gas, back to idle and it will take off just fine.

Chalked it up to the qjet being old, I now have a 1406 on the engine. It happened once this spring on a hotter day, tossed on a new fuel filter and it has been fine.

We were out yesterday and it was nearing 90+ when we went to leave, took off and it nearly died again. then it took off just fine.

Am I just experiencing vapor lock in the system or my fuel pump taking a crap? Current fuel / water separator has ~ 15 hours on it.

 

[HT32BSX115]

Re: loosing power on take off on hot days

Howdy,


Well, you do live in a part of the country that has "winter" gasoline. That means the vapor pressure is considerably higher in the winter time. Using that fuel in the summer can cause vapor lock problems in hot weather with a hot engine.

Now having said that, you also have a high time engine and fuel system.

High time on the engine wouldn't make much difference, but high time on the fuel system could....... Your fuel tank likely has a fuel pickup screen and anti-siphon "valve". The screen could be plugged (or partially plugged) with debris or you could have a plugged (with bugs/bees/etc) fuel tank vent line. or "bad" fuel pump etc.

 

[jopes]

Re: loosing power on take off on hot days

I would think any fuel I put in the tank from last November would have been burned off with 15 hours of engine time this year?

When you say high time are you meaning a lot of hours? If so the only items that have that is the fuel pump and tank. Engine and carb were new last season.

 

[Don S]

Re: loosing power on take off on hot days

Pick a nice hot day and run it with the engine cover off and see what happens. What is your temp gauge registering on those days?

 

[Oshkosh1]

Re: loosing power on take off on hot days

Two words...Density Altitude.

It's an effect which you MUST be aware of when flying in high and hot conditions.

Basically an normally aspirated engine will not produce the performance it would at lower, and cooler altitudes. Many pilots have died as a result of not realizing this. ANY engine... boat, aircraft, car, etc... is subject to this.

Could be an issue in this case(high and hot conditions) as Douglas(as I recall) sits somewhere around 5ooo feet or so.

 

[jopes]

Re: loosing power on take off on hot days

Pick a nice hot day and run it with the engine cover off and see what happens. What is your temp gauge registering on those days?

dash guage says 120. But I will have to confirm that the next time I am out with a IR temp probe.

 

[Don S]

Re: loosing power on take off on hot days

dash guage says 120

Shouldn't be that low. Get an IR temp gun and check the engine. You should be seeing in the 165 to 175? range on your instrument panel gauge, and the IR gauge. Check right next to the temp sender to see if the guage is reading right.
If it is reading right, you need to put a thermostat in it. Sounds like someone took it out to cool things off. Probably still overheating, just the gauge says it's cool.

 

[jopes]

Re: loosing power on take off on hot days

It could very well be the sending unit, I had 140 in it when I put the engine in last year, then went up to a 160 since I do a lot of slower speeds ie: trolling and just cruising, with very little water sports.

 

[HT32BSX115]

Re: loosing power on take off on hot days

I would think any fuel I put in the tank from last November would have been burned off with 15 hours of engine time this year?

When you say high time are you meaning a lot of hours? If so the only items that have that is the fuel pump and tank. Engine and carb were new last season.

Years and hours on the fuel system makes the (in-tank) fuel screen, anti-siphon valve, and fuel pump suspect..........Any fuel you had in there from NOV, would have been burned off AND, the longer it sits (in your tank) the higher VOC components of gasoline do evaporate off making it less susceptible to vapor lock. Sometimes the gasoline suppliers have higher VP gasoline they haven't sold by the time summer rolls around and you can still get some that can be a problem. In recent years ALL US gasoline has had the vapor pressure lowered by enough to probably eliminate the problem for most of us.....(EPA mandate)

Your problem might be a clogged screen in the tank, filter, and/or fuel pump problem.......as old as your boat is, you might have contamination in the tank.

If you're at 5000 MSL, (like Oshkosh1 indicated) you're only making about 70% power to start with. So any other problems will be compounded

 

[jopes]

Re: loosing power on take off on hot days

maybe I will run this tank down and try using a different in town for a few months to see if that helps out. if not I will take the tank apart and see how that looks.