85 150 Carbs on 92 150 motor

[sriner86]

I recently found out that my 150TLRQ has non original carbs on it. From research they look like the carbs from a 85 150HP engine (6G4-14301-02-00, 6G4-14302-02-00, and 6G4-14303-02-00 going from top to bottom).

The intake manifold part numbers are the same and the reed assembly is the same as an 85 200HP.

Is there any harm or decrease in performance from running this carbs opposed to the 6R2's?

WOT appears to be great, it only has a miss at idle that I've been trying to fix.

[panasonic]

How long have you had this engine and how much have you ran it?

Hard to know if running different carbs will cause long term problems. But if you have been running it for a long time like this and it has not caused any problems...should be OK.

Are the plugs a good colour?

[boscoe99]

I don't anyone will be able to see, smell, feel, taste, observe any difference between the various 150 carburetor part numbers that have been used over the years when installed on a 150 Yamaha.

As panasonic notes, check the plugs to see what can be seen. All of the carburetors can be adjusted and/or different jets installed to accommodate either minor variances within a motor or for atmospheric conditions.

Then think about all of the motor heads that are installing non-OEM carburetors on their automobiles with no ill effects being seen.

More than likely someones 1992 carburetors got damaged and it made more sense to install second hand probably used 85 carburetor part numbers than to buy new carburetors from Yamaha.

[sriner86]

I've had the boat for 6 years. Plugs look good. I noticed the bottom 4 were slightly wet while the top two were dry after idling on the flusher. Which brought me to look at that top carb thinking it wasn't fueling properly.

It's always had a cold start issue and a slight miss at idle. But has ran great off idle. I figured the older carbs are fine, but just wasn't sure. I'll see if there is any setup difference between them. I had set them up per the manual for a 1992. Maybe these ones need different settings.

Thank you.

[panasonic]

To get a good read on your plugs here is something you can try. Its called a "Plug chop" You put in a brand new set of plugs , warm up the engine of course, go full throttle for a bit, and kill the engine while wide open. Now take the plugs out and have a look at them. They should be all the same colour.

Now this might be a bit problematic doing with a boat out floating around and how hard it is to get at the plugs. I done this many times on motorcycles after modifYing jetting, exhaust pipes, ect...

But it sounds like you got a dirty carb or incorrect pilot screw settings giving you your idle problem.

If you try the plug chop test, wear your life vest and take your old plugs and two plug wrenches with you in case you drop something overboard. Would not want to see you stranded.

[boscoe99]

I looked up the jet sizes for a 1985 and 1992 carburetor. As might be expected, with the later year model the jets are smaller. Someone might have been having problems with the later year carbs, due to the smaller jets, and installed the earlier carbs to solve what might have been a lean run condition.

Normally folks will simply install the larger jet sizes. But who really knows why your motor was modified. It shall remain a mystery.

1985 jets = #130 and #90

1992 jets = #124 and #80

[sriner86]

From what the broker told us, it had brand new carbs installed. So I'm figuring these were on the shelf and fit. No idea why it needed new carbs.

I found the correct carbs on ebay, but if these ones will work I'll just keep them. I will do a better plug reading once I can get it out on the water again.

It looks like all the timing and idle screw setting are the same between the two years. The plugs and the float setting (one float vs two floats) are different.

[boscoe99]

I am seeing that the idle mixture screw settings are not the same. Even with the use of the smaller idle mixture jet, the idle mixture screw is turned a bit further inward on the later year model.

[sriner86]

Oh your picture is showing slightly different from the manual i found for 84-96 Yamaha's on boatinfo.no

I'll try carb settings for the earlier carb with new spark plugs (either the B8HS-10 or the B7HS-10) and see how that behaves and looks.

[FabricGATOR]

I would follow the specifications for the currently install equipment. After all, the only function of the carb is to atomize the fuel in the ideal mixture for the volume of the cylinder.

Lean is lean and rich is rich...

The idle (pilot) screw adjustment is not only a process of the jet installed but also how that particular pilot screw and seat is machined into the casting. So use the adjustment for the carb installed. Also, that specification is only a starting point to get it running so it can be fine tuned to correct idle response.

Throttle chop and colour check is what we do on the motorcycles when ever we change the way an engine breathes. Aftermarket exhaust install, other than OEM air filter/air box, ram air scoop.... The goal (or procedure) is to run at a speed and cut the ignition (and disengage the clutch) and coast safely to the side of the road and check you sparkplugs. You can then change individual jets in the specific carburetor to get your motorcycle running right.
There is even such a thing as a temporary test sparkplug with a quartz window on it that you can see the flame color in the cylinder as the engine is running at idle and adjust that carb for optimal idle performance. (See Colour Tune)

I do not see any problem with running a different year carburetor as long as it performs well. Besides, with all the ethanol contamination in this nations fuel supply, it is probably only a matter of time before you may need new carbs at a later date.

Find out which cylinder has the misfire at idle and work from there.

[sriner86]

Oh your picture is showing slightly different from the manual i found for 84-96 Yamaha's on boatinfo.no

I'll try carb settings for the earlier carb with new spark plugs (either the B8HS-10 or the B7HS-10) and see how that behaves and how the plugs look.

I agree once properly setup it should all function the same. I just found out this past weekend that the carbs were different.