Hoping for help! What am I missing???

[projectDr]

Hoping for some ideas or help cause I'm stumped so far.

I've got a '92 OMC 115 HP Quietrider VRO (V115SLEND) that idles fine but won't rev up under load. Seems like I'm stuck in SLOW mode but reading thru the posts it seems like 1992 doesnt have SLOW??

I can't get my engine to rev up past 2500 RPMs under load,. It will rev up smoothly with no problem getting past 2500 rpms while in neutral or even in gear when running it with earmuffs out of the water (No Load). I checked spark with a timing light w/o a load and there was spark to all four cylinders so I'm assuming the coils are OK. (But, I haven't done so under load yet) I tested the alarm horn to both temp sensors and the alarm horn works OK when grounding the leads. Additionally it seems to run at a reasonably cool temp. (I did change the impeller when it was rebuilt because I was getting an alarm after running it a few minutes on earmuffs during flushout) I do get water coming out of the pee hole OK and it doesn't overheat at all in the water at any time. I also disconnected the leads to the temp sensors and that made no difference under load. Runs a bit rough like it might have an inconsistant miss while under load but runs smoothly back @ idle. (even in gear)

Here's some background...
I had the powerhead fully rebuilt professionally a little over a year ago. New pistons, parts etc. Carbs rebuilt then too, and it generally ran OK initially with the exception of a bit rough idle (but I was running double oil (Oil in gas as well as the VRO tank) during the break in period. I was diligent in varying the speed etc during break in but in total I have run it maybe 8-9 Hrs total since the rebuild. (Trailered & Garage kept in between uses)

Last two times I've taken it out I couldn't get it to rev up under load with one exception where it started to rev up past 2500 RPMs while running @ WOT . (Figures I'd be in a slow speed zone then so I couldn't "let er run")
Since that one time pickup" occured I figured perhaps I had fouled plugs or something related to having run double oil in the past so I pulled the (new Champion QL77JC4 @ rebuild) plugs, cleaned them well and reinstalled them. Started up @ home fine and idled well. Next trip out I experienced the same SLOW type running situation occuring. It burns a lot of fuel too during a run @ WOT even though I can't get it past 2500 RPMs. I even cleaned the plugs half way thru the short river trip but it made no difference on the return trip. One more thing. I pulled the air intake hose off while running @ WOT and the RPMS did surge up a little when it got some additional air. I assumed that was because it was running so rich @ WOT and due to the fact that the very rich exhaust fumes were choking it out a bit in the closed up QuietRider housing. I've been load testin it with the cover off to ensure that it's breathing OK.

So, after that long winded tale of woe is there any suggested path I should pursue next? Maybe check the spark from each coil while under load?

My next thought might be to pull the carbs, but since nothing changed after the rebuild I'm guessing that they might be a lower probability? I think I've also ruled out the fuel pump by pumping the bulb while running it under load @ WOT (No change positively or negatively)

What am I missing??? Any ideas?

Thanks in advance for any suggestions!

 

[ezeke]

Re: Hoping for help! What am I missing???

Need the results of your compression test when you have them.

Were the carburetors rebuilt when the engine was?

 

[projectDr]

Re: Hoping for help! What am I missing???

Thanks, Yes the carbs were both rebuilt. Kind of assumed the compression would be fine after the rebuild , but I'll give it a check and report back

Thanks again

 

[captbjack]

Re: Hoping for help! What am I missing???

i noticed that you cleaned the plugs. i have had situations where the plugs will breakdown under load i would try new plugs first.( easy and cheap) hope this helps.

 

[ezeke]

Re: Hoping for help! What am I missing???

Since the carbs are recently rebuilt, lets assume your throttle plates may not be working correctly and take the cover off the carburetors for a look. Have someone move the throttle arm to full open while you watch the plates to see if they go to a perfect horizontal (WOT) and are perfectly synchronized.

If the plates are working correctly, check to see that your spark advance is connected up next to the flywheel. Again, have someone advance the arm while you watch the advance at the engine.

 

[jay_merrill]

Re: Hoping for help! What am I missing???

Check to see if all four cylinders are running rich. This sounds like a carb problem in general but it sounds more like junk in one or more of the high speed jets. This can happen easily enough and the fact that the carbs were recently rebuilt doesn't make any difference. If all four show signs of running rich, junk in the jet probably isn't the issue. I don't know your carbs but I am going to guess that they have fixed high speed jets - that makes the rich condition somewhat curious.

PS: I think Ezeke and I were posting at the same time. I think he has good suggestions too.

 

[projectDr]

Re: Hoping for help! What am I missing???

Thanks gents, I'll check the items and put in new plugs too if nothing else shows up. I'll report back.

 

[projectDr]

Re: Hoping for help! What am I missing???

OK, here's what I found. I pulled off the cover on the front of the carbs to check to see if they were both opening up fully. In the process of doing that I caught view of a very small curved piece of plastic lying on the lower cowling roughly under the area of the carb linkage. Since it was curved I traced my way up to the groove that the spark advance rides in on the throttle arm. Turns out that the roller and sleeve had broken apart. The sleeve way still there so it was.nt initiall obvious. I installed a new roller and gave it a water test with success! I might still need new plugs because it seemed to have a miss initially and didn't pick up right away. Once it warmed up it seemed to clear out and rev up OK though.

Many thanks to all of you for your excellent contributions!

 

[Silvertip]

Re: Hoping for help! What am I missing???

Do you have the primer solenoid valve turned to manual by any chance?

 

[ezeke]

Re: Hoping for help! What am I missing???

One last thing that you might want to look at is that the wiring under your flywheel has enough freedom to allow the spark advance to work smoothly.

 

[projectDr]

Re: Hoping for help! What am I missing???

Will do,

Thanks!

 

[projectDr]

Re: Hoping for help! What am I missing???

Silvertip, I think it's correct. It's pointing straight in in towards the carbs