1997 Suzuki 150 HP EFI V-6

[JSMoore]

A friend of mine has a 1997 Suzuki 150 HP EFI V6 outboard on the the back of a 21 ft. center console boat. The motor has been giving us a couple of problems. And, since there is no Suzuki mechanic any where around here, we are trying to figure out some of this on our own. Any advice or ideas anyone cares to contribute will be appreciated.

Here's the two problems:
1. Rough idle - won't idle very long without quitting. Won't hold idle in gear for very long without dieing.
2. At speed, motor develops good power and runs smooth with WOT in the mid 4k rpm area. But, will occasionally "drop" a cylinder for a while. Then, it will pick back up on all 6. It does this in a completely unpredictable, random way.

Plugs have been changed. When checked, plugs look light tan - no oil, carbon or build up.
Fresh fuel, several times weekly. (boat is used A LOT!)
Replaced water separating fuel filter.
No issues with oil pump.
Runs on Hi-test auto gas, (no ethanol free gas convenient to our area)
Motor is used so much, we don't bother with fuel treatments.

Any suggestions where to look?
Thanks!
JSMoore

 

[JSMoore]

Re: 1997 Suzuki 150 HP EFI V-6

Ideas, anybody?

 

[99yam40]

Re: 1997 Suzuki 150 HP EFI V-6

Not really that up on the Suzukis but as with all motors checking the basics will not hurt compression, spark, and timing. Testing fuel pressures and vacuum will show if there is a restriction some where.
With all the different sensors on these things makes it necessary to get a service manual and test things like they lay them out . Also testing the sparking system should be laid out in the manual and tell what test equipment is needed.

I have a friend that had 2 97 DT150s on a 25' Stama , but he sold it. I believe he still has the manual and quite a few spare parts from when he popped a piston on one and ended up putting on a 98 DT150 replacement to sell the boat. PM me if you would like to get in touch with him

 

[Tcrum5711]

Re: 1997 Suzuki 150 HP EFI V-6

Moore-

I've got a '03 version of that motor. Mine was acting some what similar with the running rough and not liking to idle. Ended up being the needle and seat in the cap of the vapor separator tank was leaking and pumping fuel right into the intake manifold though the evaporator line on the top of it. I changed out the diaphragms in the low pressure fuel pumps also which one had a tear in it and was pumping fuel into the motor also. Still doesn't like to idle occasionally but it's much better.
Mine will "drop" a cylinder during WOT runs also. I chalk it up to the computer sensing the high RPMs and lowering the RPMs to save itself. Usually does it after four or five miles of a good run.
Mid 4's seen pretty low for WOT. Mine is supposed to be 5200-5600rpm. Might be part of problem also.

 

[JSMoore]

Re: 1997 Suzuki 150 HP EFI V-6

Ok. Thanks for the ideas. I have zero experience on these EFI motors. So, I'll show my buddy these responses. BTW, Tcrum, I think his WOT rpm is low too. Seems like the motor wants to run - but something holds it back. Thanks again!