Yamaha 150 TRXC vibration issue

[Psalm 99]

Engine is a 2-cycle 2004 Yamaha 150 hp. Engine vibration pretty much doubles when in about mid range rpm (2000 - 2300). Idles nicely and runs smooth and strong while cruising (around 3000 + rpm). Thought I had problem solved as the small on-board fuel filter, while looking real clean, would hold fuel without draining. Used a jet of compressed air directed from inside surface. Vibration went down a lot but still there, even after replacing the filter. Fuel line, plugs, fuel pumps new with-in a year. Remote fuel/water separator just changed. Figure two choices: (1) Pull carbs, run thru sonic cleaner, rod out jets. (2) Try shock treatment with Ring Free (Nice write-up on Forum). However, I use Ring Free continually and a little on the high side (about 1.5 oz/10 gallons fuel). Always use non-ethanol fuel. Any thoughts before I get into this would be appreciated.

[TownsendsFJR1300]

Have you since drained the carbs, caught what came out and inspected?. Maybe squeeze the primer bulb (to flush) and see if any crap comes out..

Did you find any crap in the under cowl and other fuel filter when you drained them?

Any work done to it just prior to the issue?


It does sound like a carb has a piece of crap in it..



Re quote: "small on-board fuel filter, while looking real clean, would hold fuel without draining."

As we don't know the exact model of it, on this parts fisch: http://www.boats.net/parts/search/Ya...UEL/parts.html

the under cowl fuel filter shouldn't empty. It stay's about 2/3 full.

If you can post the complete model # may help too...

[Psalm 99]

Thanks Scott: I didn't drain the carbs, should have known better. Have had lots of problems with this engine due to it sitting for a long time with bad fuel. But for the last 6 months, its been working fine. I'll drain the carbs and check for junk as recommended. Sort of looking for an excuse not the pull the carbs but I've gone thru this before (about a year ago) using a sonic cleaner. If I do end up pulling the carbs, is there a picture available which show access to the jets? Thanks for the help!

[Psalm 99]

I should have been more explicit about the fuel filter. As the plastic screw-on cup which surrounds the filter is full of fuel, I simply removed it and the filter element but left the fuel in the cup. Then I dunked the element back into the cup. When I lifted the element, the fuel remained trapped in the element. Using compressed air, I blew the element surface out applying the air to the inside surface of the element. When dipped into the fuel after this, the element did not hold fuel. Figured it was fixed but I ordered and have since replaced the plastic filter element.

[Psalm 99]

Drained all six carb bowls and used primer bulb to flush fuel out of drains individually. Fuel looked clean although one bowl had a very small (about 0.10" dia.) water droplet. New fuel from primer use was clean.

[amahaork]

First check timing Slow idle and fast idle marks? Are you sure all coilsfiring properly at all rpm? Just observe and compare strobe light for every coil and compare.

[TownsendsFJR1300]

Being it sat for quite awhile, then been good for 6 months and the fact you did find some water (not much, but enough) some suggestions.

I would probably start with a stronger dose of Ringfree. You may luck out depending on what the crap(if a jet is slightly clogged). You can simply use a 6 gallon auxiliary tank, vs filling the entire built in tank.

I use a product called K100 which any water in the tank, suspends it and it eventually gets burned off.

My fuel tank is 1997, 60 gallons, and has NEVER been removed. I did drain it FULLY about 2 years ago (35 gallons or so), had an issue(spark plugs).
The fuel looked/smelled like new and was close to 2 years old.. The K100, IME, does work very well. All I run is RF and K100 as the stabilizer.

The third video: Demonstration | Fuel Additive | K-100 is very interesting (and shows what I posted). You can buy a small bottle. I buy a case(quarts on-line) but some marina's and motorcycle shops carry the product.

Cheap and much easier than pulling carbs and certainly can only help. If that doesn't fix the issue, I suspect you may have to drain the fuel tank(at least to inspect the fuel), and lastly, pull the carbs.


**Quote:
I've gone thru this before (about a year ago) using a sonic cleaner. If I do end up pulling the carbs, is there a picture available which show access to the jets?

I gather you simply dunked the entire carb(s) without disassembly (or you'd know where the jets are- accessible after the float bowl is removed)

The sonic cleaner works good BUT you still have to disassemble it including the jets.

If you look above, on this page in RED, is purchase Yamaha parts. Click on that, follow entering your year, model then the carb pic. It'll show the carbs, ONE broken down completely showing the main jets, idle jets etc.

The carb is NOT CLEAN until YOU can see light thru all the jets. Simply dunking or a spray of carb cleaner don't count... Do one carb at a time (dis-assembly) should you need to refer back to one for assembly (or comfy with it)

Also, the carbs "were cleaned" (not really), prior to sitting for another 6 months... Non stabilized ethanol fuel can go bad in as quickly as a month and varnish up a carb. It wasn't mentioned about a fuel stabilizer so even if the carb was correctly cleaned awhile ago, it very well could have varnished up again. "Gas Shok" IME is also a great stabilizer. I've had a bad experience with Stabil many years ago and won't use it. They may have improved it since, sooo...

Good luck and please post back.

[Psalm 99]

I'll certainly get some K100. Because I've had so much trouble with the engine, I'm real cautious about letting my fuel sit. This really is a great engine, just some understandable maintenance issues. Little history: got the boat used about three years ago. No prior history as I got it off E-bay. Boat is a 20.5' HydraSport Lightning CC with a 80 gal. fuel tank. Engine only ran on two cylinders at first. If I'd just drained the tank when the boat arrived life would have been much better. Engine had 325 hrs on it when I bought it and I've put about 250 hrs on it since. I did disassemble the carbs somewhat as the floats were grossly out of whack and the seats for the needle valves leaked badly when the floats where correctly adjusted per mechanics manual. Used a small pyramid shaped diamond rasp (Harbor Freight, about 600 grit) to gently (shaft between thumb and forefinger) buff valve seats. Tested with a mini-vac on the fuel intake and weight of float holding needle on seat. Took a number of efforts but finally got all seats to hold 20+ psi which stopped fuel from pouring out carbs when primed. I also installed new needle valves. This was about a year ago. Along with the new fuel pumps, plugs, cleaning my ground wires, and reducing the fuel line (with new line) from about 16' to 4' (relocated the fuel/water filter), the engine has been pretty good. This vibration issue is livable but as it just recently happened its an indication that something is wrong. The fact that the needle valve seats where so compacted makes me think that, although the engine has been running ok, maybe a full disassembly of the carbs is in order. I did reference the pic of the full carb on the Forum's site as I order my parts there but I was wondering what's under the two large brass plugs (part 21 on the pic). I thought maybe there were some areas which I hadn't accessed but which needed attention.
I'll make up a batch of R-Free & gas (think 2 oz/gal was recommended). I have both a 5 gal and 2 gal gas cans. You mentioned 6 gallon. I'm running at home with the engine on muffs. I'll run about 1500 rpm. Would the 2 gal be sufficient? Once again, thanks for all the help. - Al

[TownsendsFJR1300]

Correct, 2 oz per gallon for RF shock treatment... I would do the 5 gallons.

I'd personally prefer to run the engine in the water with varying RPM's. Of course run it quite a bit in the "rough RPM range" trying to clear out whatever may be in the carb...

On some of the smaller machines (chainsaw, weed eater, etc) I've worked on, I left the RF shock mix in the engine(and carb) overnight and let em soak... I had noticeable BETTER running just doing that... Had to re-adjust the carb to accommodate the better flow as well.

IE, Maybe run it some on the muffs, then the next day, put it in the water and run it...

Perhaps with the issues you had with the needles sticking, etc, some varnish built up, causing some sticking, etc. The RF should help with that...

Besides cleaning the fuel system, it's also cleaning the top end of the engine as well...


If the fuel is currently good, get some stabilizer in there. Any doubts, dump it and make sure the tank is clean...

[Psalm 99]

Thanks Scott; if you notice a wispy cloud of smoke on the western horizon this afternoon, it probably me and the engine.

[TownsendsFJR1300]

I was just watching You Tube video's of engines blowing up, lots of smoke, parts flying and flames!!! Funny as heck...

Don't you make it on You Tube!!

[99yam40]

getting flow thru all passages helps clean them , but the idle and off idle ports/passages are the ones the plug up more often as they are smaller.

i have found large pieces of stuff ( looked like thin plastic sheet)that may have come from lines/pumps that turned loose and hit main jets before, but it is not something that happens often

[pstephens46]

I am betting those carbs may need some special attention.

[Psalm 99]

Definitely some special attention at this point. Engine wouldn't start with high RF solution. Finally got it to sputter a few times. Removed front plastic cowling and noticed, when using the primer pump, fuel dripping out the trapezoidal shaped port at the front of the lowest carb. Figure its trouble with the needle valve seat again. Real puzzle: Went to turn off water to muffs and had a good-sized very black oil slick riding on the top of the ground water. Figured my lower unit was leaking but that oil sump was full and real clean when I checked. I did work for some time on the starter trying to get the engine to fire, and I'd expect maybe a little oil out the exhaust as the engine wasn't firing; but this stuff was black as pitch and seemed excessive. Rough guess I turned the engine over about 100 times trying to get it to start. I'm using good Yamaha 2-cycle oil and I've checked the oil pump linkage and cam. Everything seems ok. Sorry for the extra problem. I'm going to let the RF solution sit in the carbs and engine for a night then pull them all for a through cleaning. Any advice will be very welcome

[99yam40]

flooding carb is washing out carbon and oil from cylinders and exhaust.

is there a reason you did not replace the seats instead of trying to modify them