Mariner 150 2 stroke need help please!

[Gremos90]

Hey everyone, I'm new here and new to outboards. I am very mechanically inclined though.

So here's the nitty gritty. It ran really good on muffs in the yard, put it in the lake and it falls on its face and dies as soon as you come off idle. I maybe got 8km/hr and for a 150 that's pretty embarrassing.

I checked compression on all 6 cylinders and they're absolutely beautiful (120-130). I have spark on all 6 as well. I pulled apart the carbs and cleaned everything up, except they weren't dirty at all. I replaced all the fuel lines and one of the fittings because it was cracked. Cleaned out the fuel tank, put new fresh fuel, put a new fuel filter.

It sputters under muffs in the yard now. Not a consistent idle/throttle when I crank on it.

How to set the throttle? How do I set the idle? How do I set the air fuel mixture? I was told my jets are the kind of jets that you're supposed to tighten all the way in and leave them there, not turn them back at all? Essentially how to get this thing to SQUARE ONE?

I really don't know the year of the motor but the boat itself is a 87.

 

[AVI_8]

Sounds like fuel starvation, or air getting into the fuel, when you rebuilt the carbs did you dismantle all the carbs and blow them through with carb cleaner, check the float needle valves. You mentioned that you closed off all of the carb jets, did that include the idle control jet, if so I’d double check that they normally get backed out around 1.25 - 1.5 turns.
Check the fuel pump diaphram.

Have you got a service manual, itll tell you how to set up the carbs for your particular engine, once you’ve got the serial number you can probably find it here
https://forums.iboats.com/threads/service-manual-index.447812/

 

[Gremos90]

Sounds like fuel starvation, or air getting into the fuel, when you rebuilt the carbs did you dismantle all the carbs and blow them through with carb cleaner, check the float needle valves. You mentioned that you closed off all of the carb jets, did that include the idle control jet, if so I’d double check that they normally get backed out around 1.25 - 1.5 turns.
Check the fuel pump diaphram.

Have you got a service manual, itll tell you how to set up the carbs for your particular engine, once you’ve got the serial number you can probably find it here
https://forums.iboats.com/threads/service-manual-index.447812/

Here's the thing theres (unless I'm retarded) only two adjustments per carb, I have to pull a plug out and screw the jet in or out. Atleast that's what I've come to find out. I don't have any adjustments on the carbs themselves that I can find at ALL. The only thing that changes the way the motor runs is ... This....thingy.

 

[jimmbo]

Well, you just learned that running Great on Muffs means Nothing, these engines will sound fine running on 3, even 2 Cylinders when on the Muffs. No Backpressure. Put it in the Lake, it is a different Story.
Does it have a Spark the can jump 3/8", on all cylinders?
Does the Fuel Pump supply enough fuel?
You had the carbs off, did you make sure the Sync between the Carbs and the Timing was still good? In fact, does the Timing advance when the throttle is moved to full throttle?
How did you set the Floats"
That thing you circled in red, is the Fuel Enrichment Valve/Solenoid that replaced the Choke System
I would guess your engine in in the 1980 thru 1984 years.

 

[Dukedog]

tha motor looks ta be an '83.. its second gen power head but still has single cylinder TnT..

you need to find an OEM manual for it... by your own words your lost on what and how to do stuff on that motor.. there are no adjustments to those carbs.. they have an "idle circuit and an off idle (high speed) circuit" that can only be changed by changing jet sizes.. tha idle speed/rpm are controlled by changing "idle timing only".. that needs ta be done in tha water and in gear... this is jus tha start!.. ya need ta know tha link n sync procedure (done before ANY timin', idle or max, is done) etc. ............. jmo