merc 200, running poorly

[2182]

just got this boat/motor, ran well at test. first time driving, she started up kind of rough, then ran great (3000-5000 rpm) for a half hour or so on and off. when i brought it down to idle speed it died. restarted, drove some more, died again when brought down to idle speed. killed battery second time trying to get her going. changed plugs and gas line filter today, wouldnt start in driveway or ocean. its a 92 motor but was rebuilt a few years back and looks very clean/well maintained. im not much of a mechanic but any simple ideas im missing? id appreciate anything, dying to get a fish (or 20) on her.

[shawn1127]

dont no if it helps try taking fuel hose off tank and get portable tank w fresh mixed fuel give it a try might have lot off h2o in tank may take awile if you have h20 in carbs
if it starts to run any better your problem is in the fuel
empty tank and clean. ethonal is killing everything that floats may have to clean carbs i took a can of seafoam to 6 gal of fuel hooked up the muffs and run it thru it worked well i have a 4str should work w/ 2 str hope it helps

[fdheld34]

I have a 1993 Merc 135 hp..same block as 200 etc. I purchased engine about a year ago fresh water only and it ran great when I first got it as well..same symptoms as yours. I replaced fuel tank, lines filters etc but to no avail. Took it to mechanic and he had to rebuild all three carbs....gunk in carbs...said engine was sitting a while and then got clogged up....now it runs/idles etc like a brand new engine. Find reputable mechanic and take it from there...I am not mechanically inclined so I cant offer any more advice. Only thing I can say is don't mess with engine yourself if you dont know what you are doing..will screw it up worse..especially linkage etc.
Fred

[JohnB]

Sounds like junk in the carbs. When they sit, the gas evaporates, and leaves a film/layer of crud in the bowls, especially if it sits a long time. When you run it again, the gas loosens it, and it gums up the jets/etc. Actually, pretty common. Sometimes you can hold your hand over the throat, and it will "clear".

[2182]

cleaned out the carbs, shes purring like a kitten. they were deceptively clean from looking on the outside. thanks for the help. now all she needs is a tarpon hanging over the side and we'll be in business. not sure if you guys ever use this site for motor stuff but "iboats.com" has forums for just about anything and is easy to search.

[Bigshrimpin]

224466 - how fast is that 18ft'r with a 2.5L 200?

[gofastsandman]

Might wanna file a flight plan!

[Bigshrimpin]

I sold a 1992 Mariner 2.5L 200 offshore (with a Magnum III cowling) to a customer today. We bolted it onto Donzi sweet 16.

[2182]

too fast...i havent got her out on a super slick day yet, hopefully tomorrow am is cooperative. low 50s (on gps) so far. also still adjusting to having trim tabs on a boat. guy i got it from said she went 62 or so.

[Blue197320]

i want to get one of those 2.5 power heads and replace my 2.4 when it pops.