highspeed problems

Ok, so I finally got my boat to idle perfectly and it does great at low speeds. I cleaned out the gas tank and all the gas lines, and now I am having trouble when my boat is going faster than 20mph. It goes good, then when you reach about 20 it's like the throttle drops and the boat will die. What could be the problem, is it my fuel pump, or could it be something else. Also how do you pressure test a fuel pump and what should it be at?

Check your MAP sensor. What is the RPM's? Sounds like the boat is going into limp mode. .02

I guess you 82 is carburated, right?

Sounds like fuel supply is unable to keep up. On a carb, volume is more important then pressure.

5-8 psi, but cant remember the volume.....been so long since I've messed with a dinosaur

What size jets are you using and what is your altitude? Did you clean the carb as well?

(Message edited by olSkoolTige on May 13, 2008)

MAP sensor?!? LOL along with the flux capacitor and the independent suspension. Sorry, but thats funny as hell.

Ever replaced the fuel filter?

And how far into the rebuild did you get?

Just replaced the fuel filter and i'm pondering over the rebuild. We got a mechanic friend of ours to come out and "tune" the carb. and it seems to be working great now. Seems like a fuel issue to me.

Glad you got a kick out of that nacho.

http://en.wikipedia.org/wiki/MAP_sensor

I don't check profiles because they are not always right. From what I have experienced, that was and can be a potential issue with the newer boats. .02

ok, well it can't be the MAP sensor. Even though it is a real thing, it is not on my 82, so it must be something else.

I am pretty sure it is my fuel pump, but is there anything else it could possibly be.

checklist completed: tuned carb, changed fuel filter, cleaned gas tank, cleaned fuel lines..

sounds like fuel pump is only thing left, since everything else has been gone through? i haven't worked on carbs for awhile but TM is right, you want more volume than pressure to feed that hungry little guy.. should be an easy DIY job to replace altogether if you got tools and some skills..

I'm well aware of what a MAP sensor is bro.. and that's why it was funny. I wasn't implying that they don't exist, but that you would not find one on Brandon's boat.

Kee & Manfox, the fuel pump is mechanical. operated by the fuel pump eccentric which bolts to the front of the cam. check the clear tube that runs from the fuel pump up to the carb. If you see gas, then you need a new diaphram inside the pump. other than that, there's not much that can go wrong.

back to the rebuild, I would guess...

fuel pump is showing 7 pounds of pressure. Is that too much? And even if it was, I don't think it would cause this problem.

All lines are clear and the carb is clean, I don't know where else to go from here.

One more thing, I temporarilly bypassed the gas/water seperator due to a crack in the canister it fits in, so it's not on there. But I don't see that being a problem either. It will be back on by this weekend, so I guess I will at least see if that helps the case.

to me, it seems more like there is air in the lines, so it is not getting enough gas, so you guys says its more volume than pressure, what would be a solution to feed the carb more volume?

any chance you got water in the gas line when you removed it? is it airtight?

I think thats your problem... any water or air in there would cause you to lose power. replace the separator. if not, then have your carb guy do a complete rebuild.

i'm pretty sure there's no water in there, but how could I see if there is air?

I don't know where the air would come from, there's no leaks in the gas hoses, where else could air be coming from?

well Denver, since i'm trouble shooting, when we taking your boat out. i'm a good driver. LoL

(Message edited by trickyboarder08 on May 15, 2008)

Nowhere other than a small leak. the fuel pump's vacuum could pull it in. Not likely, but since you mentioned the separator, i thought I'd throw it out.

My boat: sent me the wrong rotation cam. doubt I'll have it by NEXT wknd.

"temporarilly bypassed the gas/water seperator due to a crack in the canister it fits in"

Could be sucking air, this would give you accurate pressure, but low volume as air is easier to draw then.

how could no gas/water seperator cause it to suck air?

Definitely not trying to argue with you, I believe you 100%, but was looking for a reason this could cause it to suck air.