90 hp merc 4 stroke w/ carb stalls when accelerates

[stockman157]

I have never had any problems with my engine until I let it sit 3-4 months one winter. My mechanic changed the fuel pump-tuned it up and changed the oil. When I first started it it sounded differnet--I am not mechanically inclined! as i pulled out of the marina and went to accelerate it stalls out. I put the boat in neutral and it reves up all the way and seems fine. Its only when it is in gear that it stalls out when it hits 18 on the rpm gage. My mechanic chrged e another 150 to tell me that the carb had gottenall gummed up and needed to be replaced--as I recall another 800 for a rebuilt carb-i have been running carb and engine cleaner thru the engine hopoing to clean it out and now it goes up to 28 RPM and at times it sounds as if its about to cut loose but then stalls. Been doing this for about a week--when shood I give up and bite the 800 dollar bullet?? Any advice wood be appreciated.

 

[MercFan]

Re: 90 hp merc 4 stroke w/ carb stalls when accelerates

Could very well be a dirty carb, but as with anything dirty, you don't replace it, you just simply clean it!<br /><br />You can try de-carb cleaning spray, but it's probably best to remove them, strip them, and clean them.<br /><br />Take pictures and make notes as you remove them and open them to make it easier to re-assemble. You probably have more than 1 carb, keep them seperate, do not interchange parts, and put each carb back where it was.<br /><br />The most complicated (and it's not that complicated) is the needle and seat assembly. About 5 small moving parts.

 

[Texasmark]

Re: 90 hp merc 4 stroke w/ carb stalls when accelerates

She (the engine) is telling you that she is thirsty. 3-4 months of sitting is not all that bad unless you had old fuel and the problem became aggrivated because of it.<br /><br />I personally doubt that with today's fuels with their built in injector cleaners and all will turn to puke in 3-4 months. What your problem may be is old fuel that you let set 3-4 additional months and now you have a problem; not with gum in your engine/carb and all, but in your fuel tank.<br /><br />Before I'd spend a dime on any repair work, I'd drain your tank, refill with fresh fuel, put in some carb cleaner....Berryman's Chem Tool, Marvel Mystery Oil, Sea Foam, to name a few; like a quart of it to 10 gallons (overkill to get things cleaned up). Run that for a few hours at WOT or as near as you can get and then reassess your concerns about needing and $800 repair job. <br /><br />You lost nothing but a little time and $15 bucks worth of fuel and conditioner; but you may have saved the day for yourself. If you start getting improvements, just do it longer. It's telling you that you are on the right track, just haven't gotten to the goal posts yet.<br /><br />Mark

 

[Boatwizard]

Re: 90 hp merc 4 stroke w/ carb stalls when accelerates

Try this before breaking the bank. Buy a can or two of Powertune, Mercury makes it. Take the drains out of the carbs, let it drain and put the plugs back in. Take the fuel lines loose at the carb side of the fuel pump and spray the powertune in the hoses to fill the carbs. Put about 2/3 of the can in. Spray, let the foam disapate and spray some more. WEAR safety glasses, this stuff will light you up if you get it in the eyes or in a cut on the finger. Let sit over night and drain. Watch the green goo flow out. Repeat procedure again. <br />Also the lines have a tiny strainer inside them behind the carbs that may be plugged. You have to remove all the carbs to clean or remove them.<br /><br />$800?? How do people do that? I'd get shot if I charged that.........

 

[admar]

Re: 90 hp merc 4 stroke w/ carb stalls when accelerates

i have not posted in quite some time and i thought it was time to chime in again. time to let the worms out of the can. <br />first let me address texasmarks comment ""I personally doubt that with today's fuels with their built in injector cleaners and all will turn to puke in 3-4 months." sorry to disagree, it may take that long in texas but here in south florida, during the summer monthes, a month is all it takes to gum up a yamaha carb, maybe six weeks if you are lucky. yes yes i know ed adkins has a mercury 90 hp 4str. ,yamaha builds the powerhead and it has yamaha carbs. on it. the fuel in the tank is also most likely bad and should be replaced. but no amount of fuel treatment and rev tuning are going to fix his problem, although it could lead to a scored/ denotanted piston damage from running at wot. from a lean mixture. definitly not the proper fix or advise!<br />mercfan has got it right. you don't need to replace the carb if it is only fouled and gummed up, only cleaned and rebuilt with correct kits and proceedures. ed you stated that you are not very mechanical?, so i assume you are not going to attemt the repair yourself. 4 stroke carburetors are more complex than those on 2 strokes and do require factory manual and special tools to properly syncronize after they are clean. with out 4 bank vacuum gauge or a manometer the chances of correctly setting them are zero!! if you marine only wants to replace the carbs find out why they cannot clean and rebuild. if they say they can't, find a shop that has the right tools and is willing to do it, i do 20 or more merc/yamaha 90 hp carb. jobs a year,plus too many v4/v6 motors to count.<br />and to finish. boatwizard you question the $800 price but not the reason, while i do not condone or agree with replacing a carb in need of cleaning and rebuilding, i do question you. you are a tech , correct? then why the shadetree post? if this industry is to ever overcome it's bad reputation that it has rigthfully earned from those who don't know how or care to do the job right, we must do our best to encourage proper repairs. ed's shop is not to be critisized for it's price, but for it's reason!!<br />as a side topic , the pricing for a job like this in my shop would be approx.: (labor- 5hrs @$85 removal, tear down, inspect, clean, assemble, install, syncronize,water test) parts: (about $100-$120) shop supplies$6. for cleaner and consumables/misc.) and because i am set up to do dockside service and will for this type of work a service call of $40. is also added if the customer want the convieance of not having to bring the boat in to the shop. this fee covers all travel to and from boat location as much as needed. plus state sales tax, that here in florida is collected on the entire invoice at a rate of 6% brings the total to... $626.46<br />if you provide quality service and work then there is no need to fear getting shot at, nor should you go broke.

 

[MercFan]

Re: 90 hp merc 4 stroke w/ carb stalls when accelerates

Ed,<br /><br />I didn't pay attention to the fact that you are running a 4 stroke. And I'd agree with Admar and others. Don't tear down the carbs.<br /><br />Go with Texasmark and Boatwizard.<br />Drain your fuel tank and fuel lines as best possible. Get new fuel in the tank mixed with seafoam. And do a overnight soak in Powertune.

 

[stockman157]

Re: 90 hp merc 4 stroke w/ carb stalls when accelerates

thanks to all for the sage advice!<br />Ed

 

[Boatwizard]

Re: 90 hp merc 4 stroke w/ carb stalls when accelerates

It depends on where you're located admar. Shops around here do charge 500-800 dollars for such a job. They sit and drink coffee in May and I'm 2 to 4 weeks behind. <br />AND DON"T EVER CALL ME A SHADETREE PARTNER!!!!!!!!!!!<br />After 23 years at the rate of 500 to 600 jobs a year, and only averaging 1 comeback a year, I think I can hold my own against anyone. Heck the average marine shop in the USA has a 90% rating, we have 99.8 with the only bad marks being the boat came back a little dirty. I take my work serious and get jested about it. My motto on work is "My work reflects what I stand for, it WILL be right.". If I could get the rest of the guys to feel that way, we'd be heck on wheels.

 

[admar]

Re: 90 hp merc 4 stroke w/ carb stalls when accelerates

boatwizard, it was not intened to be personal, and shadetree was probably not the adjective to use. the intent was to raise question to the fact that i have read many of your posts and can tell you that you no what you are talking about. you and i also know that THE only way to know that a carburetor is clean is to open it up and inspect it properly, with the knowledge of what to look for. i was only trying to illustrate that fact. sorry for the poor word choice. <br />p.s. and yeah the power tune trick does work ---- sometimes.

 

[Boatwizard]

Re: 90 hp merc 4 stroke w/ carb stalls when accelerates

We have about sixty 90 HP 4 strokes running around here. The majority of their problems are dirty carbs, plugged line strainers and a fuel pump spring or two. The Powertune trick works about 90 percent of the time. The only other thing we've had is the shift cut out switch. <br />The 90's have been a good engine with a unreal bulletproof ignition, still haven't seen a problem with it.<br />I do know it takes about 5000 gallons of gas to wear one out.