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2007 30HP 2-stroke Mariner - Troubleshooting Strange Idle + Cut out at WOT (Vids)

Q

QLDTOM

New member
Hi,


I have a 2007 - 30HP - 2 Stroke Mariner on a 399 Stacer Proline Hull.


I took the boat out for my first test run and i was running it on and off for about 3 hours, cruising for 10 minutes at a time in between spots.


After a few hours i decided to head to the top of the creek, so i was running at WOT for about 15 minutes when the motor seemed to mis-fire or have some kind of issue resulting in the motor cutting out (Large vibration and the motor kicked/wobbled too)


I could not get the motor to start again (Coasted to ramp with Minn-Kota)


When i got home i drained the fuel (95 Octane from Caltex) and replaced it with stock standard 91 Unleaded with new oil - I also drained the Carb and removed the old 95 from the other hoses and gave it new spark plugs.


I can start the motor again and it Idles but the revs appear to drop and then come back.


I have cleaned the Carb and it seems immaculate, all the jets and needles are cleaned too.


The IDLE is set on the Carb correctly from what i know as when its running well there are no problems, its the drops in RPM that have me questioning the motor.


Either i assume its ok and take it out again or i book it into a boat mechanic to pay out the butt for a look over - I dont know if im just over thinking it or not.


It is hard to start as well - i hope the running-videos may help someone determine if it sounds ok.


The only strange thing i can notice is that the roller-cam that actuates the arm on the carbie has been wrapped in electrical tape to increase the the the WOT top speed - If i remove that tape the boat only does 28-30kph - with the tape it does 42kph
(The tape just seems to help push it slightly further to the WOT position)


carb arm.jpg
carbiue2.JPG
Tests/Info/Video Below:

https://www.youtube.com/watch?v=IaxSNOVYgCY - Idle Video showing RPM Drop
https://www.youtube.com/watch?v=fXQUnTor_Ao - Video of 2 minutes of running with revving etc

Cylinder PSI:
Cyl1 = 155 PSI
Cyl2 = 160 PSI


New Spark Plugs BR7HS-10


Cleaned Carbs/Jets


Cleaned/Replaced Fuel Filter


Replaced Fuel Hoses

comp test.jpg

30hpmercmarin.JPGoutbaord2.jpgoutboard1.jpg
 
Last edited:
..." i was running at WOT for about 15 "

Are you kidding! You think that's an electric motor that can run wide open all the time? You need to back off a bit, to breath the motor.

I suggest a compression test to see how much damage has been done.

Jeff
 
fastjeff said:
..." i was running at WOT for about 15 "

Are you kidding! You think that's an electric motor that can run wide open all the time? You need to back off a bit, to breath the motor.

I suggest a compression test to see how much damage has been done.

Jeff
Click to expand...

Hey mate, by WOT i just mean at general top speed, not over cranking.

Compression test results are in the post as well as pictures.
 
I am going to check my owners manuals to see if there are any warnings like-----" Do not run at full throttle for more than 3 minutes at a time "
 
In your list of checked/replaced/cleaned I didn't see where you included checking the fuel pump bladder - if not, worth a look and check for restriction/crud in the hole that leads into the crankcase behind the pump itself (which drives the pump with pressure).

I did hear the rpm reduction at idle - sounds like a fuel starvation problem of some sort. You may also want to run a finger under the flywheel and check for a "gloopy residue" - a toasted upper crank seal, which would allow fuel/air/oil to escape could be the issue. The other thing I would check is for similar residue right in the bottom of the lower cowl - that would be looking for a toasted powerhead base gasket, although that is usually accompanied by a "sneeze" when it is shot.

I don't think this model has a transfer cover (but am not positive). On other twin models that gasket would be suspect as well.
 
galamb said:
In your list of checked/replaced/cleaned I didn't see where you included checking the fuel pump bladder - if not, worth a look and check for restriction/crud in the hole that leads into the crankcase behind the pump itself (which drives the pump with pressure).
Click to expand...

Will double check everything in your post - Thank you for taking the time to reply i will report back.
 
QLDTOM said:
Will double check everything in your post - Thank you for taking the time to reply i will report back.
Click to expand...


Well don't I feel dumb.

When I bought it I was told the tank and line were new but it appears only the tank is new.

The hose was filled with some kind of plastic material.

I hope to test again tomorrow on the water and can mark this solved I hope.
 
I have seen the inner liner of fuel hoses collapse and cause a restriction.....I mean like serious restriction, there was a bulletin about it years ago with the introduction of ethanol fuels.
 
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