95 Yamaha 225 powerhead break-in

[mcm114]

Ok, I just bought this engine that came with a rebuilt powerhead and refurbished lower unit. I put 2 hours on it so far following the break-in procedure using a 50:1 ratio in the tank. (It has the precision blend injection system working as advertised.) Is there any reason that a combined 25:1 ratio would cause the engine to perform relatively poorly, i.e. rough idle, sluggish, slow to plane, and surges? Because that's exactly what she's doing. Also, this dealer says that he normally removes the thermostats on these type engines, because they're not needed. It seems to me that the engine would have a hard time getting up to the proper operating temp without thermostats. But I don't know. Maybe there is a compression issue until the rings get properly seated? I guess what I want to know is, how smoothly should I expect this engine to perform for these first few hours?

And since this boat is primarily a ski boat, normally operating with moderately heavy loads, is there anything I should be doing differently right now besides varying the RPMs? At what point should I try pulling a slalom skiier (heavy+fast), or a kneeboard (light+slow)?

 

[bgbass.1]

Re: 95 Yamaha 225 powerhead break-in

ok here goes at 25:1 it will run rough.you should run it 25:1 for 1st 10 hours. for first 10 min. in gear at fast idle,next 50 min. rpms below 2700 vary engine speed at least every 15 min,during 2nd hour use full throttle to plane boat quickly then reduce to 3/4 or less try to stay on plane.vary speed at least every 15 min.at different times go to wot for 1 to2 miniutes then back to 3/4 throttle to allow pistons to cool dont go back to idle.for next 8 hours continue to vary speed no continuous wot for long periods.after 20 hours it should be broken in. change gas to run on injection pump change plugs. you should be all set. i know its long but it will last a lot longer.

 

[rodbolt]

Re: 95 Yamaha 225 powerhead break-in

50/1 in the tank and precision blend WILL NOT cause it to run rough.
its broke.
depending on the model number the T-stats are a critical part of the system. in anycase they should be in place.
rings really dont seat on a two stroke, it was either finnished honed correctly or it was a cobble job.
after the ten hour break in its done. yamaha has no 20 hour checks.
sounds like someone is pulling your chain. look for the school certificates on the wall.
if they are not there maybe prayer will help at this point.

 

[mcm114]

Re: 95 Yamaha 225 powerhead break-in

I just did a search and found this thread from 5 years ago...

Quote from "dcato":

My Yam 225 (carbed and oil inj.) is running rough and almost stalling when in gear from 1200 through 1800 rpms. Once it makes it through this range it smooths out and powers up quickly. It also sputters (skips) at higher rpms occasionally when underway. The powerhead was recently rebuilt and I was running extra oil in the tank for the break-in. Could it be fouled plugs or maybe a carb or fuel pump problem? I have checked filters and lines and all that for leaks and debris. Any help would be appreciated before trying to get a dealer to look at it.Thanks

This is verbatim the exact same problem I am having. And here is the one reply, from "Solittle":

I would suspect a bit of crud in the carbs until the high speed jets open up. That compounded by the increased oil. Might want to wait until the breakin period is behind you and you are back on the normal fuel-oil mix before you do anything.

--------------------------------

I'm going to run it with straight gas (briefly) tomorrow, and see if the problem goes away. If not, I will then pull the thermostat housing to investigate that situation. How do I know if thermostats are "critical" or not? Is it computer related, like a lower operating temp effecting the ignition timing?

 

[drewmitch44]

Re: 95 Yamaha 225 powerhead break-in

I agree with rodbolt. There was a whyle at the begining of the season that i was running my 115 with 50:1 and also the presision blend system. It neaver ran rough. It smoked a little at idle when it was cold but ran fine. I was doing this because i was not sure that the precision blend system was working right. I did this for about 10 to 15 times out. It costed me to add oil to the tank but it just smoked a little more and that normal if there is too much oil. It wont hurt it though. Id take it to the guy that rebuilt the motor. Thats crazy not to use the t-stats. Suppose you use the motor in cold water, you could crack the block or head by the water being so cold on a hot block. Thats what i was told anyway and as a matter of fact its listed the same on my clymers manual. Get the t-stats that could be the problem if its not getting up to operating temperature. And was any work done to the carbs, timing, fuel pump system when it was rebuilt?? These are all questions i would ask the guy that rebuilt the motor.

 

[mcm114]

Re: 95 Yamaha 225 powerhead break-in

Your comment about the cold water contacting a hot engine block...I always held the assumption that water is in the engine block as long as the water pump is working, and the thermostats open for circulation when that water reaches 118-126 F. Am I wrong here?

 

[mcm114]

Re: 95 Yamaha 225 powerhead break-in

Update:
I was just reading my manual which states, "The enrichment system on the 90 degree 225 engines is controlled by a microprocessor. Throttle position and temperature are monitored and enrichment is automatic."

That is all the information the manual provides. But it seems likely that this gizmo could be constantly enriching my fuel:air ratio because of a low temp condition. Yes/no/maybe?

I ran this engine for about 2 hours today and I attached a thermocouple sensor to the cylinder head (various places, same readings) and the surface temperature never exceeded about 97 F. I ran it for several minutes then checked it at idle (no one at the helm, ya know). That tells me that this engine probably does not have working thermostats, because it should be at least 118 (lower limit for the thermostats to open) and below 194 (upper limit to activate the overheat sensor).

 

[rodbolt]

Re: 95 Yamaha 225 powerhead break-in

as you thoughtfully neglect to give a model number none of us can tell you which system or even displacement yamaha your running, there are at least 4 versions over the years.
like I say, prayers are in order about now as your rebuilder seems to have cobbled it.

 

[mcm114]

Re: 95 Yamaha 225 powerhead break-in

'95 powerhead (225TLRT) 2596 cc (plus .020 overbore)
'91 midsection (including power tilt/trim)
'91 computer, knock sensor, other misc electrical components (225TLRP)

 

[rodbolt]

Re: 95 Yamaha 225 powerhead break-in

how did I Guess
the TLRP electronics and fuel system is what we need, the 95 was vastly different.
your setup should use 2 fuel pumps and an enrichment pump. check the enrichment pump diaphram. without Tstats it will always run rich , its designed that way.
normal operating temp on that engine is 120-140*F. much cooler and like most all loop charged 2 strokes of any make and it runs like crap,especially at low speeds.
I love it when monkey techs re-engineer a decent product then wonder why it wont work right.
over the years I learned if you return it to the specs that the engineering dept stated it works correctly first time everytime.
did the happen to check the recirc check valves at overhaul? most techs dont even know they exist on the 2.6L blocks. if they fail it idles nasty and likes to foul plugs.

 

[mcm114]

Re: 95 Yamaha 225 powerhead break-in

This engine has two diaphragm fuel pumps and the electronic enrichment pump. The carburetors and everything else in the system are exactly the same as my old 91. I have not checked the enrichment pump, other than lifting the little red lever, which apparently disengages it because it causes the engine to sputter and die at idle.

What are the recirc check valves, exactly?

Lately, I haven't been having too much trouble at idle. Yesterday it idled pretty smoothly, it just smoked a lot. But I couldn't push it over that 1300-1500 rpm threshold (where the boat planes out) until it had idled for 10 minutes or more. At WOT I'm only getting about 4600 rpm. Could that be caused by a low temperature/rich mixture?

 

[rodbolt]

Re: 95 Yamaha 225 powerhead break-in

no,
its most likly caused by dirty carbs,bad low pressure pumps or the diaphram for the "so called" electronic pump " that aint electronic at all. the output of the pump going to the carb enrichment circuits are controled by the A and B solinoids. the pump is still a diaphram pulse type pump.
the check valves are in the block, 3 on each side.
that enrichment valve is operated by the ECM for several reasons,2 not attached to temp.

 

[mcm114]

Re: 95 Yamaha 225 powerhead break-in

Oh yeah, the "bleed system", the 3 hoses on each side of the powerhead? I will look into that. I didn't know there were check valves either.

The carbs were supposed to have been cleaned, so that shouldn't be an issue, but who knows for sure. I haven't done anything with the enrichment pump, so that could be it. But I still don't understand exactly what the A and B solenoids are supposed to be doing at that exact point in the RPM band, 1200-1500. I could replace the pump with the one from my old engine, just to see what happens. I could do the same with the carbs for that matter. One thing at a time, I suppose.

 

[mcm114]

Re: 95 Yamaha 225 powerhead break-in

THROTTLE POSITION SENSOR!!!!!!!!!!!!!!!!!!!

I started poking around with my multimeter today. Thermo-switches, thermosensor, knock sensor, all good. I couldn't get a steady resistance reading on the TPS, and sure enough there was too much corrosion in the connector for the probe to make a solid connection. I robbed the one from my old engine (after resistance testing it first) adjusted to .5V with the throttle closed, and voila. No more hesitation getting on plane, and I got more rpms at WOT this time, around 5200. I'm still getting new thermostats this week, I'll report the results. Should I still take a look at the enrichment pump?

 

[rodbolt]

Re: 95 Yamaha 225 powerhead break-in

its easy to rebuild and can blow a motor if the diapham fails. if the diaphram fails the fist indication is rich runing at low speeds.
the ECU will add enrichment for knock detect as well as rapid acceleration based on TPS angle change.
when you flip the red lever it adds fuel bypassing the a/b solinoids.
check the tps carefully, some tended to develop dead spots.