Trouble shooting Merc 200hp

[steve forsythe]

If i can get some advice on where to begin troubleshooting my 2000 Merc 200hp carb outboard. It has gone through 3 powerheads (same cyl. i think-#5) since it was new. It is not under warranty any more, so i have to solve myself. The motor would run fine, then after about 20-40 minutes, die off plane and shut itself down. It would re-start but have a lot of trouble getting back onto plane. After limping in, blown powerhead---3 times. Some suggestions so far include..... not running it enough ( letting it sit for a few weeks at a time without starting - butterfly in carb sticks and fuel is restricted to that cyl.), prop size, oil restriction to that cyl. All of the obvious has been checked, like oil pump, impeller, fuel mixture, etc. Why the fuel or oil restriction to only one cylinder?? Why the same cylinder?? It is definately running lean in that one cylinder, but i dont know why.

 

[BIGKASH]

Re: Trouble shooting Merc 200hp

thats sucks man i would be so pissed if i would drop the motor at the dealer and demand to be replaced with a whole new engine period or its gonna be hell up in here,....anyway i dont really have a good sugestion other than the dealer loaning you used carb or new to replace and see if it clears up....cant really be an oil problem cause it mixes before the carbs so they would all be lacking oil, right.I would rule out the prop idea for sure.<br /><br />if its lacking fuel and while running you should be able to pull plug #5 and see no difference cause no/lack fuel no spark same running<br /><br />i'm sure the experts will chime in soon good luck and please post whatever the outcome

 

[Hooty]

Re: Trouble shooting Merc 200hp

Hey,Purse*Snatcher,<br />If tha group here runs outta ideas, try these guys.<br /><br /> S&F <br /><br />c/6<br /><br />Hooty

 

[steve forsythe]

Re: Trouble shooting Merc 200hp

Should i run it in the driveway for an extended period of time, then pull the plug and see if it is getting fuel? The engine was just fixed, has not been out yet on the water, and it wont be until i find the probable cause. I might have to run it for a while to get the problem to occur again, and dont want to cause damage again. Can i monitor cylinder temp individually??? How can i run it and watch for the problem? Thank you very much, and i did e-mail Joe Smith Racing. UPDATE- tried to e-mail him but it said invalid e-mail.....I will try another way.

 

[Hooty]

Re: Trouble shooting Merc 200hp

You could probably run the engine at 2000 - 2500rpm, on the hose without a problem. As far as monitoring individual cylinder temps, NAPA has a non-contact, infrared thermometer, for about 80 skins, that would be ideal. <br /><br />c/6<br /><br />Hooty

 

[jim dozier]

Re: Trouble shooting Merc 200hp

Pull the carb for that cylinder and check the main jet and the passages. Maybe its got a main jet different from the rest. That a wild shot, but hey you have a really weird situation that doesn't sound like the run of the mill dirty carb that usually happens. It sounds from your description that there is something fundamentally wrong with the mixture going to that cylinder. Maybe there is a flaw in the castings for that carb that are interfering with the mixture if the jets are correct. I would also remove those plugs (the round discs that cover the carb passages) and look for weird blockages.

 

[Yepblaze]

Re: Trouble shooting Merc 200hp

And if not a restricted jet to thet cyl you might consider enlarging the appropriate jet size. <br /><br />Check and recheck your max advance.<br /><br />I understand there were some motors (althouth it may not include yours) that had issues with sparkplug wire induced, or other, cross firing that led to piston failures. Easy enought to check with a inductive timing light and look for additional flashes around the flywheel.

 

[jim dozier]

Re: Trouble shooting Merc 200hp

I wouldn't recommend enlarging a jet in one carb only. And I wouldn't change all the jets unless there was a service bulletin to do so. Before I would alter the jet I would by a new carb. That cylinder is running lean and there is a reason for it to be different than the others, we just need to find it. You have either too little fuel, too much air, or some part is out of spec and causing a lean condition to one cylinder.

 

[Hooty]

Re: Trouble shooting Merc 200hp

I think some Merc engines have different size jets for different cylinders (or should have). <br /><br />Check with S&F.<br /><br />c/6<br /><br />Hooty

 

[gss036]

Re: Trouble shooting Merc 200hp

I would think that Mercury would authorize the dealer to troubleshoot the problem since it all started while under warranty. I would be bugging Mercury, district rep or who ever. <br />You say a blown power head, what type of damage is being done?<br /><br />My 2 cents:<br />You say it shuts itself down, and then it will restart and run at low RPM, right? Are you getting a good flow of water? Do you have a water pressure gauge installed? I have been told that would be more important than the temperature gauge. Usually that type of shut down indicates OVERHEATING!! What does the temperature gauge read? <br />Premix in a 6 gallon can and run that way and you know for sure you are getting oil. I don't think that would hurt anything since mercury reccomends double oil for break-in on new engines.

 

[steve forsythe]

Re: Trouble shooting Merc 200hp

Thanks for the replies. The temp almost never goes over 175 & it pees pretty good all the time. The engine overheats in one cylinder, shuts itself down with no warning horn, or real change in temp. The damage was a cracked ring the first time, and badly scored cylinder wall the second and third. Compression numbers would read like ... 145-150 for 5 cylinders and 40 for the other. The carb is just a guess on my part, and the mech said maybe it is sticking, restricting fuel flow. I want to run the engine, or have him run it continously until the problem presents itself again. Should i do that ??? Or try some of the fixes first. The problem is, if i change the carb out first, then run it, how will i know if it is fixed? It could run fine for months, then happen again out on the water.<br />As far as Mercury goes, they replaced the first head under warranty, they gave me a factory rebuilt for $1600 the second time (out of warranty), and the third said basically it wasnt getting fixed correctly and they couldnt help any more. I would think they would offer some better advice, or help my mechanic!!!<br />Edit.....I have premixed before, but like i said it can take up to 125 hours until it shuts down again. The last powerhead lasted almost 1 year (100-175 hours). The pee stream is not always that great at the begining...but after temp raises from cool to 150...it starts to pee real good. I have changed the impeller. I dont have a water gauge on it. (should i??)

 

[Kenny Bush]

Re: Trouble shooting Merc 200hp

If it is scoring close/next to the exhaust port, you may want to back the Max Advance off a couple of degrees. Also as stated earlier, Merc has had a detonation problem on some motors.

 

[bret walters]

Re: Trouble shooting Merc 200hp

we need more detailed info. like what type of boat, prop size,jack plate, max rpms, type of boating , normal load, has anything been added to the boat; thru-hull fittings, transducers, baitwell pickups ect. the fact that the problem has happened 3 time means your dealer has not done their job, fire them and find someome else. replacement of power heads means transfer of all bolt on systems,fuel, oil, recirc, ignition,midsection which is also cooling water supply, the problem has to be in these systems or is boat related. <br />over propping can be a cause so don't rule it out. was the boat a package rig or dealer rigged? <br />have the carbs been completly cleaned? the throttle plate for one cylinder can not stick and lean out a cylnder, they are all connected and are 2 barrel design, its just a lame excuse for lack of knowledge. please post back with more info.

 

[steve forsythe]

Re: Trouble shooting Merc 200hp

I will try to get you all the info i can find. What i do know is this...23 foot Irvette, center Console. 97 hull, 00 engine. Extension bracket on the back holding the motor. No jack plate. Maxes out at approx. 5800 rpm's. Cruises @ approx. 3500. Usually carrying 2-3 people, full cooler, full fishing gear, livewell, in 2-5 foot seas. Dont really run it "all out", but it does go for 10-30 miles at varying (3000-4500) rpm's. There is a 50 gallon baitwell with a fill entrance on the bottom for when you are moving. There is a transducer on the rear, screwed on, not through hull. Stainless mirage prop ( not sure of the exact size) will have to check the boat and try to find out. The carbs were cleaned before this last failure, and i was told the prop was "fine" for this boat. But what do they know?

 

[steve forsythe]

Re: Trouble shooting Merc 200hp

Merctech...thank you very much for your interest in helping. I wanted to bump this to the first page so you could see i answered last night. I hope this isnt frowned upon here.

 

[steve forsythe]

Re: Trouble shooting Merc 200hp

The boat is currantly in South Carolina, but is getting picked up in a few days and brought back to Florida. I will ask more questions and have more answers when the boat is right here in front of me. Thanks again.

 

[daveanna]

Re: Trouble shooting Merc 200hp

I would say a water pressure gage in your situation is a must. I used to own a 1994 Merc 175 XRi on a Champion bassboat. I had a gage on it and it read 2-4 psi at idle but would read 19 or 20 psi at high rpm. The pee stream was somewhat weak at idle but was very strong otherwise. I think was the merc v6 characteristic. I never had any problem with that motor. Hang in there, good luck, dgs.

 

[steve forsythe]

Re: Trouble shooting Merc 200hp

UPDATE: I retreived the boat from South Carolina. I took it out and ran it for a few hours and it ran fine. It idles fine but when put just in gear, it runs rough (900-1000rpm). It shakes a little and sounds as if it is going to conk out. Anyway, I found out from Mercury that the first powerhead failure was a blown head gasket. How could that of happend? The second powerhead failure was a cracked ring in cyl 5. The latest failure was in cyl 6. I guess it ran lean?? My question from the beginning of this post is......what do i do now??? I am now adding gas stabilizer to combat any bad fuel, i have a water separator, and i keep the tank full of fuel. I have been told not to leave gas in the carbs for long periods of time (varnish/gum build up) But then someone else told me dont run the carbs dry, because the gaskets can dry up??? Should i have the carbs cleaned by someone, or can an amature do it? I dont think my engine has an overheat alarm. Where would it be, and what would it look like? Through all the failures, i never once heard an alarm, the engine just shut down and it was too late. <br />Sorry for all the questions, just very interested in solving this problem.

 

[Kenny Bush]

Re: Trouble shooting Merc 200hp

PSnatcher I feel your pain..... Hang in there and stay on target. I kept eating pistons in my 200 until I backed the max timing off 4 degrees. I lost about 200 rpm's at the top end, but I have not eaten up any pistons since then... I got this idea from a merc tech in Fond de lac... He told me to back off the timing if the pistons were scoring at the exhaust port edge. He also told me of a Factory problem with double firing. It seems to me at 5800 rpm's you are at the high end of the range. If that cylinder is dry, then none of this matters....

 

[kshatzer]

Re: Trouble shooting Merc 200hp

Keep updated on what you find as I will be very interested. I just brought a new boat (22 Sport Pro-Line CC)back from FL to TX with a 200 Merc. carbed engine on it . During the test run in Fl., it seemed to do fine but on the first time out Sun., it was doing similar things. The first time I ran the RPM's up and ran across the lake it ran like a champ. When I brought it back to a slow range and then tried to power up, it near stalled. Tried to power up several times before it finally caught. This repeated several more times during the course of the 1&1/2 hours I had it out. Once it finally caught it ran fine but it took several attempts to keep from stalling from low rpm to a cruise setting. Thought it might be a normal thing with the double oil during the break-in period but the FL. dealer says it shouldn't be. ??????<br /><br />Ken