v-6 dt 150 problem

[lifetime62]

just bought a boat with a v-6 Suzuki 150 . changed all 12 spark plugs, fuel line and bulb , added premium gas and going down the lake running 4000 rpm's it will cut back to 2000 rpm's , need help

[Solarman]

dt150, age?, carbs?

Can you give a little more info on motor? Age? Are there any codes flashing on monitor gauge? Does it have carbs? Tell tale? The dt does tell me it's 2 stroke, the RPMs going from 4k to 2k sounds like it might be going into limp mode? Could be fuel related still, but need more info from you.
Help us help you.

[lifetime62]

the motor is a 1991, don't see any problem on the guages , i did change the fuel line and bulb , it does have carbs (3), they looks great i have 125 compression on all cylinders , this is a 1990 sprint bass boat , it don't have guages per say ,

[Moonlighter]

Some extra description of the circumstances of how it starts, runs and accelerates, and when it cuts out, exactly what it does, and how it re-starts will help us to help you. Is the fuel bulb flat, full of fuel, normal when the engine cuts out?

The more info and details, the better so someone here can make some informed suggestions for you.

So far, all I could suggest is possibly that you may have a fuel restriction problem, and for you to check the simple, cheap and easy things first:

1. It could be as simple as a partial blockage in the tank breather, causing it to starve when held at higher revs for a while. So check the breather hose and the breather outlet, often those mud wasps can make nests in there and block it up. Also check that the breather hose has no kinks etc in it. Blow thru it if possible to make sure it is all clear.

2. It could also be a partial blockage or failure of the anti-syphon valve, which is on the fuel tank pickup on most US boats. Remove the barb and clean and check you can blow easily thru it one way, and not at all the other way. If in doubt, you can either replace it or punch the ball, spring and seat out and reinstall it as a straight-through fuel barb.

In both of these cases, it would be likely that the bulb would be squashed flat when the engine stalls.

[Solarman]

dt150, 1990, running issues

You have two fuel pumps on that motor. Do you have a manual to test both pumps? Have they been inspected/ rebuilt, checked for damaged check valves inside? First, I would test both to make sure they are pumping fuel properly. If not I would inspect the check valves (not replaceable, 2 in each pump, must replace pumps if bad). If check valves are good, then rebuild both.
Let us know how the test comes out. If both pumps are good, well move to next step, trying to find out which cylinders are cutting out.
Does your motor NOT have a monitor gauge on dash?
Good luck.

[lifetime62]

the fuel source it looks as if someone has already remove the anti-syphon valve and connected it straight , I didn't see the bulb goes flat when it cuts back , it only cuts back right when you get to 4000 rpm's , I will check the breather hose tomorrow get back to you, I have no manual to check or even where it is on the motor , I will try to find a manual

[Moonlighter]

I was referring to the fuel tank breather hose. Goes from the tank to a fitting on the outside of the hull, to allow air into the tank as the fuel level drops.

[lifetime62]

breather

I was able to check the breather and there was water in and I did blow it out , going to take it out tomorrow and see if that helps , cross fingers ,, how do you replace the filter behind the oil container

[Moonlighter]

If there was water in the breather line, there is a fair possibility that water has gotten into the fuel tank and, from there, into the engine's fuel system, or at least into the filters.

Do you have a water separating fuel filter - like a RACOR style filter, fitted? If so you should check that filter and see if it has any water in it. Drain, check for any water, and replace the element.

Not sure if that is the filter you are referring to that is behind the oil tank, but if it is, they are just a spin-off filter, so an oil filter wrench will get them off. A smear of oil on the rubber gasket is required when they are reinstalled.

[lifetime62]

run it today and still doing the same thing, it doesn't have a water separator on the boat , just a fuel filter and then the one behind the oil injector tank on the motor resevior this one is little and clear

[Moonlighter]

Ok, well I think the suggestions others have made should now be followed up. Fuel pumps etc.

I would just reiterate that it really is imperative to have a really good water separating fuel filter fitted, separate to any in the engine itself, on your boat, RACOR make good ones that have a clear bowl underneath that allows you to see and drain out any water. Mine is fitted near the transom, between the tank and the primer bulb. I change the element annually as part of routine maintenance.

So after you get this issue sorted out, that would be high on the agenda.

[Solarman]

dt150, 1990, running issues

Grant the one on the motor behind the oil tank, is the fuel filter on the motor. He may have the water/fuel filter on the boat. It is a water separator and fuel filter combined. If I read him correctly.
Lifetime, if you have any water getting into that breather line, then good chance your filter has some in it. If it was fuel in the breather line, then it may have a loop in the line, that is below the tank. If you fill the tank, and it overflows through the breather then that fuel should fall back into the tank. If either water or fuel get trapped in that vent line it should be checked for flow problems.

[BillCon]

When your running and hit 4000 rpms and as soon as it starts to cut back, push the key in, that will dump fuel into the lower two carbs that is stored in fuel primer pump on top of the engine, if it picks back up, your problem is fuel flow related, if it doesnt then its a fault circuit related problem.

[lifetime62]

I ran the motor at the ramp and I can put a rag in the right side on the top carb and it don't change , same on the middle carb. it didn't change at all ,still died at 4000 rpm's.
it does have a filter on the motor and i am having it changed

i bought a separator and put it on.

[BillCon]

I, also have a DT150 they are real hard to diagnose at idle because they sound like a mini dragster on steroids, I, can pull off plug wires on mine and it still sounds very close to the same, but take it to the ramp but dont unload it, run it under a load about 2000-2500 rpms you can tell a lot more that way, start your diagnosing there with the carbs under a load, you could qlwo have a reed valve acting up when it gets hot, but im guessing you have a fuel related issue, let us know what you find in that test