DT 65 WOT problems

[jkovacev]

Hello,

My DT65 was working great at any throttle position until after about 20 min of use today, now it does not go above 1300 RPM? the throttle linkage looks good, fuel is good, fuel filters are good, the fuel pump was replaced about a month ago. I have no warnings oil is good

I was trying to check if the prop and the motor were correct. It looks like the motor is a little to deep and might need less pitch as RPM never went above 3200.

After the forth run and getting to 36mph we slowed to a troll then tried again but this time it would not go past 1300 RPM. THE SUZUKI gage was reading fine. I checked the oil in the tank and it is going down so I know it is burning oil.

[artdf175]

This almost sounds like a fuel tank vent problem
When this problem occurs, what is the fuel bulb doing?
Does it go flat?
Another thing to try to observe would look at the small inline fuel filter
See if there is any air in this indicating a hose connection problem
Art

[jkovacev]

The flue bulb is round, and there is no air in the fuel filter in motor.

[Solarman]

When you replaced fuel pump, did you examine it? Why was it replaced? What else have you done to carbs?

When it only went up to 1300 rpms, what did it act like/ do if you pushed throttle forward farther? Was it running smooth up to 1300 rpms?

It sounds like either it's going into limp mode, plugs acting up (do you have an old set you could run for a test), fuel restricted (why I asked about pump), or maybe a TPS.

With some additional info, it might help us.

Good luck, post back when able.

[jkovacev]

The fuel pump diaphragm had some cracks so I rebuilt it as well as the (carbs were in major need of a rebuild) and replaced the plugs. The reason for this is the boat sat for three years outside in UT with a full tank of gas (GAS PUMPED OUT and lines pumped out). After this it ran great for 15 hours.

It was running great at 1300 RPM we had to run for about 15 min at this to get back to the dock but it did not matter how much we pushed the pushed the throttle forward it did not make any difference. Once I got it home I started it to flush out the motor and ran it for about 10 min. the RPM was able to get to 3000 but did not push past that.

[artdf175]

what year is this engine?
here are some things that come to mind
3,000 RPM .. when you say "flush out"
was this in a tank or with a hose connection?
running in neutral?
should never be run over idle on a hose connection
running in neutral .. the rev limiter will not let it go any higher

did you change out the fuel line from the tank to the engine?
I have a 2006 kicker and the internal part of fuel line was disintegrating and plugging the flow and creating a lot of other problems.
all this from the alcohol in the fuel..
Art..

[jkovacev]

1986 DT 65
It was both side feed hose and it was in neutral.

I have not changed any lines from the tank to the motor. I did not see anything in the fuel filter on the motor. the lines look to be old. there not hard or cracked as what you would thing if running Alcohol based gas.

I also replace the impeller and the gear oil (it did not have any water in)

[artdf175]

the rev limiter kicked in is the reason it would not run over 3,000 RPM
however,, be very careful.. it is my understanding the manual will tell you not to run while on a hose. just not a enough water flow is he primary reason.

The outside of the fuel hose is made of a different compound that the internal side.. It is not terribly expensive to replace and if it sat for 3 years, it could have some build up restrictions..
Might double check the carbs and make sure you, again, blow out the ports effectively . 3 years is a long time to sit idle without having problems..
does your boat have an internal tank or run off an external one?
If it is internal.. double check the air vent for the tank.. with it sitting for e years, little critters find small holes to call home..
Art

[jkovacev]

Good to know, about the water.

I will replace the fuel line, bulb and check the vent line. The tank is AL 22gal the pickup is welded in to place so I can't remove it and check the screen. I know the vent does not have any sort of screen on it. I know the fuel/water separator was about 10 years old.

Thank you.

[artdf175]

you can use compressed air to blow out the tank vent.. just be careful because you can slightly pressurize the tank and can get blow back..
replacing the fuel hose is good periodic maintenance, especially if you appear to be having fuel related issues.. and not really sure how old it is to start with

if you are too far from a river or lake that you can back into, some dealers have a basin you can back into to run the engine at wot ..

and obviously if you have taken apart the carbs make sure they needle valves are set back to factory settings and should only need very minor adjustments

good luck and let us know how you do..
Art..

[Solarman]

OK, you didn't replace the fuel pump? You rebuilt it (the check-valves are not included in the rebuild kit.). Open up that pump and look at the clear discs (both check-valves) in the lower section. If those check-valves are cracked, broken, or missing the pump won't work well. And, im guessing those fragments of the check-valves are in front of the needle valves restricting fuel flow into each carbs float bowl. (You would need to remove each needle valve seat to find all the pieces, then reset float height for each carb.)

Art, not sure if the '86 had the neutral switch, or rev limiter then?

Check these things and post back. Good luck.

[artdf175]

Solarman, you are correct, I am not sure about neutral switch or rev limiter ..but something to be checked into.. you mentioned the "limp mode" earlier, which is essentially a rev limiter..

Good to know, about the water.

I will replace the fuel line, bulb and check the vent line. The tank is AL 22gal the pickup is welded in to place so I can't remove it and check the screen. I know the vent does not have any sort of screen on it. I know the fuel/water separator was about 10 years old.

Thank you.

with regards to this comment .. you say the fuel/water separator was about 10 years old.. so when did you replace it? .. as you may know, this is an annual replace item.. If you were running on the old one, I can only imagine having problems. would be very plugged up..

and also suggestion to to test fuel source problems.. get small external tank, maybe 2-5 gallon type and plug directly to engine and see if you have same results.

And Solarman mentioned your fuel pump.. a couple of years ago I had a problem with my fuel pump on a non-Suzuki kicker.. I took the hose off the pump that goes to the carb and put the end in a container and started the engine. got virtually nothing to pump out.. replaced the guts and got a full steady stream of fuel.. one way to test the output ..

art..

[Solarman]

If you could borrow, use a portable tank, this could tell you if it is the on-board tank, and then you could focus on that. But certainly the fuel filters need to be upgraded, 10 years is way past time.

Art back then ('86) the motor could have had a flow switch for a heat sensor that would cause a limit situation ,but not any neutral switch.

Good luck, post back when able how it's going.

[jkovacev]

I replaced the fuel filter and water separator after I drained the fuel tank as the gas was very old. I replace the float switch as I was getting water flow reading problems and once I took it off found out it was broken. the water flow switch fixed the water flow reading problem.

I have rebuilt all three carbs and set then to factory settings. this worked great for over 10 hours of use. Then went out with my son and it worked great for an hour; then stopped in the lake for about 15 min once I restarted it would not go more then 1500 rpm. it ran fine just would not go over 1500.

Also should the spark plugs set to the minimum spec?

Very Respectfully,

John

[Solarman]

It ran for ten hours, then stopped for some time, and then wouldn't run over 1500 rpms. Could something be stuck in the flow switch?

I'll look at your parts pages to see what else might cause limit to kick in. Ok, in parts page it shows a throttle switch (look in the service manual on testing and check.) It also shows a throttle sensor (the service manual may tell you how to test this?) Either of these may limit your motor to 1500 rpms. The fuel pump/ system might limit you also, but I think you would have surging up and down if this were a problem.

Check these things and let us know.

Post back when able to let us know.