1994 DT65. Hard wiring oil tank level sender

[JohnOrrett]

Hi all, I posted a while back about this engine throttling back to 3,000 RPM after running in a swell. No alarm or anything and new plugs fitted. I'm taking the boat to a marine agent for servicing, new impeller etc. but came across this comment relating to the DT65:

"the 2-stroke oil tank level sender has a tendency to give up and put the engine in limp home mode despite a full tank of oil. Replacements are expensive, but it's cheaper to blank it off and hard wire the plug so the system thinks the tank is full all the time."

The mechanic thinks it may be a fuel issue, sucking in air maybe, but says that he will have a look for me. to try and pinpoint the issue, I'm tempted to try the above to see if that makes any difference. Has anyone a wiring diagram to show how bypass the sender. Would pressing the red reset button help? (not ideal whilst out at sea though).

He also mentioned a couple of things - something on the middle carb that might be an issue. Would this be something to do with the mixture? He also said that some engines have a switch at the front of the engine. The one we have just seems to have a blank hole!

Any help appreciated

Thanks,

John

[Solarman]

Hi john, what you've described sounds a lot like trash in a tank getting sucked into the carbs, it could also relate to the oil level sensor in the tank if it is going bad? There are test procedures in the Suzuki service manual for those sensors.
It is easier to buy/download one of the manuals, it has the wiring diagram for your motor. Does your suzuki monitor tell you a code when rpms are limited to 3k? Usually given in two sets of flashes, then it repeats the code until it is repaired.
The carb mixture screws should never be changed. They are set by the manual/factory specs, and are only functional at idle speed. All three mixture screws set identically. If the carbs have been apart, the jets on some older models have different jets between the carbs from factory (carbs were balanced to each cylinder by the jets). If the jets get mixed up, the carbs may not run evenly at higher rpms.
I would not recommend disabling any sensors, as the ECM will always look to read those sensors.

Good luck. Post back when able to let us know how it's going.

[JohnOrrett]

Thanks again Solarman. I doubt if it is trash from the tanks. They were brand new plastic containers with fresh fuel. The engine had been running for a good while until the revs dropped down to 3,00. Research shows that the oil level sensor can cause an issue, hence the thought of someone else to bypass the sensor and keep a close eye on the oil level!

I think the mechanic must have been talking about the Throttle Valve Sensor, as it looks like that is on the middle carb.

No codes, no alarms, no flashing lights, the revs drop, normally when in a swell whilst at speed. I have also now bought a manual for the motor. Will wait to see nwhat the mechanic says in a few weeks. We are taking the boat to Ireland in a few weeks so wanted it checked out before then. We have a solid backup Honda 5hp as well.

[Solarman]

Have been to both threads, will stay with this one.

If you can post in detail, exactly what's happened/ happening, and all that has been done to correct the problem, all items tested, or replaced. We might be able to assist you to locate the problem.

Post back when able.

[JohnOrrett]

Update - engine went in for service. Carbs cleaned in sonic bath but were in fairly good shape. However, the engineer said that the filter in the oil filter/flow sensor unit was covered in what he described as 'jelly' which was stopping the proper flow of oil through it. He has replaced it and cleaned out the oil tank and put in fresh oil.

Engine runs fine in the tank. We won't know for sure until we run it it on the river in a couple of weeks time, but fingers crossed.

Will let you know the outcome.

Thanks as ever for the assistance

[Moonlighter]

"Jelly" could be from inside fuel lines - being affected by ethanol fuel. How old are the fuel lines from tanks all the way to engine? If in any doubt ..... replace is a good idea. Especially if they have become a bit less flexible with age/exposure to sunlight.

And, do you have a Racor style water separating fuel filter in the fuel line between tank and primer bulb? Really good idea to fit one. We have them on the larger motors and even on the small boat with our 40hp.

[JohnOrrett]

"Jelly" could be from inside fuel lines - being affected by ethanol fuel. How old are the fuel lines from tanks all the way to engine? If in any doubt ..... replace is a good idea. Especially if they have become a bit less flexible with age/exposure to sunlight.

And, do you have a Racor style water separating fuel filter in the fuel line between tank and primer bulb? Really good idea to fit one. We have them on the larger motors and even on the small boat with our 40hp.

Hi Moonlighter. Fuel is here in the UK so standard 95 octane unleaded. Fuel lines are now new as we bought a couple of 22l hard plastic tanks to replace the old metal tanks. I did ask the engineer about a Racor but he reckoned it didn't need one. Might be worth thinking about.

[Solarman]

The racor is still a good idea, as well as running an additive in each tank of fuel, especially if it is NOT a good quality marine fuel. Some suppliers/stations purchase their fuel from the lowest outlet of the refinery tanks. This is the lowest priced fuel, but it also has the most trash.

If he has cleaned the oil system then make sure you run oil & gas mixture until you are certain oil is flowing to every cylinder properly.

Good luck.

[JohnOrrett]

The racor is still a good idea, as well as running an additive in each tank of fuel, especially if it is NOT a good quality marine fuel. Some suppliers/stations purchase their fuel from the lowest outlet of the refinery tanks. This is the lowest priced fuel, but it also has the most trash.

If he has cleaned the oil system then make sure you run oil & gas mixture until you are certain oil is flowing to every cylinder properly.

Good luck.

Thanks Solarman. We always get fuel from a proper garage, Shell, Esso, BP etc., rather than the cheaper supermarket fuel. The engineer ran a premix to make sure everything was working OK after the service. Any particular brand of additive?

[Solarman]

I buy the sea-foam additive, have not had problems with fuel.

Good luck.

[JohnOrrett]

I buy the sea-foam additive, have not had problems with fuel.

Good luck.

Many thanks, will report back in a couple of weeks after sea trials!

[JohnOrrett]

OK here is an update. Engine ran well for about 20 minutes, then revs dropped again, even with throttle wide open. I was trying to gently move the control lever a little and thought that might have been the issue. Took off the engine cover and tried to rev the engine using the throttle lever, with no joy.

I then pushed down slightly on one of the 2 throttle control rods, the 2 vertical rods. I pushed the one nearest to the boat, and the moment I did that, the engine went back to full revs immediately, and carried on running faultlessly all weekend.

Question is, by pushing the throttle control rod down, I presume that operates the butterfly in the carb? By pushing down, is it opening or closing it? Would this cause too much fuel to be in the carb and the revs reduce because of this, and once the rod moved the butterfly, it had the correct air/fuel mixture? I'm not sure what caused the rod to stick in the first place.

Thanks, John

[Solarman]

John what you are describing sounds like the choke rod, if it's at the front of the carbs, like mine. All of the choke butterfies are connected together at the mouth of the carbs. This should have a solenoid (for automatic choke) at the top of that rod. It should be activated by pressing the ignition key inwards. If your choke rod is not free to spring back to full open, or if you need to close it partially for the motor to run better, then carbs may be your problem (dirty air/ fuel pas-sages, or sticking butterflies).

Post back when able to let us know, good luck.

[Toyotatrukin]

Got a 89 or a 90 model dt65 and someone has decided to take all of the oil injection system off and just leaving the plugs undone long story short on first startup engine runs great then after about 10 seconds the cdi changes the timing and it starts running super rough, any ideas?

[Dt85drydocked]

@Toyotatrukin

"Got a 89 or a 90 model dt65 and someone has decided to take all of the oil injection system off and just leaving the plugs undone long story short on first startup engine runs great then after about 10 seconds the cdi changes the timing and it starts running super rough, any ideas?"

Was there a fix for this?