1994 Mercury 200 issues

garbubba · #1 10-09-2014, 09:46 AM

It's a 2.5 litre and has had the oil pump removed long ago. I've had issues but almost all electrical. This one has me stumped.

Starts fine, off we go, I hit the throttle & it takes off, everything seems normal. We ride along on plane for a while (from 2 to 10 minutes) then without me touching a thing, the boat takes off, increases speed and rpms.

This has been happening for a few trips now, I keep thinking I figured out something, but.. it still does it.

- does not seem to be a power pack, I've had that happen & it runs rough & slow.

- Thought maybe fuel wasn't getting to all the carbs, but I checked plugs, linkage & lines, all appear good. Besides it's running smooth, not like it's missing.

- Anytime I've been able to give it full throttle it's all there, pulls hard right up to about 5400 RPM's just like always.

- The remote seems OK, the throttle isn't moving unless I move it.

I'm starting to think it might be sticking linkage, shaking loose after some riding, could that happen?

It explains most of it but seems unlikely, I'm about to go dig into it again, hoping somebody here has some insight.

phatdaddy · #2 10-09-2014, 09:56 AM

does it stay at the increased rpm or settle back to the original? if the timing was moving,would this cause a fluctuation in rpm? might go thru a link & sync and check trigger assy and flywheel.

just shooting from the hip, a grown-up will be along soon.

RidgeRunner · #3 10-09-2014, 10:04 AM

Still waiting on grown up to be along soon.. LMAO!

garbubba · #4 10-09-2014, 11:31 AM

Once it speeds up it stays there until I throttle back.

Timing is an interesting thought. it would explain why it's running even, at least

I just came in from checking all the linkage. All looked good to me, I cleaned it up & greased it anyway.

The timing linkage moves OK, not sure what's going on under the flywheel though.

Link & sync? as in the carbs? I have a guy nearby that I plan to take it to if I can't figure anything out myself. I have him do all the carb work, first time he did was the first time this motor ever ran really well for me since it'd been neutered.

smokeonthewater · #5 10-09-2014, 04:11 PM

Link n sync as in carbs and timing

THEFERMANATOR · #6 10-09-2014, 08:27 PM

I've had problems in the past where the timing linkage would stick and stop before it went over to the stop. When it breaks loose and goes all the way to the stop it will jump up.

spareparts · #7 10-10-2014, 06:55 AM

check all the linkages and make sure none are sticking. If you see any sticky goo under the flywheel, the stator is getting hot enough to melt the varnish off the stator bobbins, that will make the timing base stick. If everything looks good, try disconnecting the idle stabilizer and check the timing. Run it with out the idle stabilizer and see if it happens again.

garbubba · #8 10-10-2014, 04:19 PM

Thanks guys, I checked the linkage & it seems OK. Everything I can see under the flywheel looks just fine. So I'll check the timing next.

steplift20 · #9 10-11-2014, 03:47 PM

You know when it goes on plane the boat will go faster just my two cents

smokeonthewater · #10 10-11-2014, 06:22 PM

when it's been sitting a few days pull the cowl... study the linkage till you find the linkage to the timing advance... without starting the engine have a helper shift into gear and push to full throttle while you watch that linkage closely.... see if it advances fully on it's own and if you can help it along if it does not.....

Years ago I had a chevy suburban w a 350 that was a real dog unless you put it in neutral and held it at wot for at least 15 seconds as it slowly revved from 3000 up to 5000 rpm and then it would run fairly well for the rest of that trip till it was parked for a few hours..... Turned out to be the mechanical advance in the distributor was gummed up and VERY slow tot advance..... half a can of brake clean, some compressed air, and a spritz of wd40 and that old junker ran like a new truck.

COULD be just as simple on your merc.