DT150 Bogging on first plane

[CAustin]

Hi. My 2002 DT150 is bogging down when I come up on a plane for the first time during a days' use. It happens like this. I put the boat in the water and it starts up fine. Runs a little rough for a minute with low rpms sometimes and can be enough to throw the oil alarm at times, then it clears up or I shut it down and start back up to clear it. I then idle out through a no wake zone for about five minutes. Sometimes it's letting out a lot of smoke when idling through the no wake zone. Then I throttle up to get the boat on a plane, it bogs down. It gains rpms slowly until the boat planes then the motor clears up and runs fine. For the rest of the day, I can go to my spots and shut the motor down for long periods, start it up and it runs up through the rpms when planing off without a single hitch.

Can't be plugs since it did this even when I replaced them last year. There is no water in the fuel. I thought about fuel pumps, but my thinking is that if it was fuel pumps, it would do this every time I plane off. I could be wrong though. My next option would be injectors, but then again, wouldn't it do it every time with injector problems also?

I've also thought about the extra smoking through the idle zone could be the engine getting too much oil at low rpms and fouling the plugs, causing it to bog down that first time plane and burning the oil off of the plugs then clearing up. But how is the pump pushing more oil than needed at those low rpms? I just remembered seeing an arm going to the oil pump from the throttle linkage when looking at the pump one day. I wonder if it can be adjusted.

Would really appreciate some input if anyone has had any experience with this. Thanks!

[T-Bone]

I have the same motor 03 model. I had the same issues you are describing. I found my fuel line was deteriorating on the inside. I also did not have a water/fuel separator. I replaced all fuel lines and bulb. Added a separator and have no more problems.

[boats.net]

Check oil pump link arm is connected and adjustment.

[CAustin]

Thanks for the help. I'll go ahead and replace the fuel lines/bulb. They look okay on the outside and feel fine but who knows what condition the insides are in. The bulb I forgot to mention. If the boat sits for at least 2-3 weeks, I have to unhook the fuel line from the outlet side of the bulb, squeeze the bulb and place my finger over the outlet, then release the bulb to draw fuel up to it. The fuel lines/bulb should have been one of my first things to look at, but my thinking is that this would cause it to bog down more than just once during a trip. It needs to be dealt with regardless.

I have a separator but the housing is old. Maybe there is something going on with it also. I'll replace it as well when doing the fuel lines. When you replaced the lines, did you replace the lines on the manual fuel pumps also or just from the tank to the motor?

I'll recheck the linkage to the oil pump. As far as I can remember, it was connected last time I looked at it when searching for an oil leak. Is the linkage adjustable? I see other linkages (throttle and shift) and they are adjustable. I just didn't pay attention to the oil pump one when I glanced over it. If it's adjustable, how would you know what's the right amount? I wouldn't want to adjust it and cause it to supply too little oil to the motor.

[CAustin]

The bulb I forgot to mention. If the boat sits for at least 2-3 weeks, I have to unhook the fuel line from the outlet side of the bulb, squeeze the bulb and place my finger over the outlet, then release the bulb to draw fuel up to it. The fuel lines/bulb should have been one of my first things to look at, but my thinking is that this would cause it to bog down more than just once during a trip. It needs to be dealt with regardless.

Ah ha! Disregard the part about the bulb. After reading a post about bulbs, I learned that it's normal for a bulb to operate like that when you place your finger over it (the outlet side). Problem is, I learned also that fuel should not drain back down to the tank. Meaning...... Air. If there is an air leak in the lines between the motor and the bulb somewhere, the fuel drains back down to the tank over time annnnnnnnd the bulb will not prime due to no negative pressure being created in the line (motor side) from the air leak. Maybe it bogs that first time on a plane from a "vapor lock" situation being created from the leak and once fuel demand gets high enough it sucks it out of the line. Sounds logical. Lets hope so!

So. Replace the lines(from tank to motor), bulb and even the separator.

[T-Bone]

I replaced fuel lines between tank and the connection on the engine. I do not have a quick connect at the motor. I did not replace lines on the motor itself. While replacing the fuel lines I found there were several splices and even had 5/16 line going to 3/8. I replaced with all 3/8 inch line. The screen filter on the motor would have lots of black particles in it and I would clean it often. That's when I realized the interior of the fuel lines were breaking down.