My Mercury 90/65 is hard to start. Not sure what else to try

[Webygail13]

I have a 2003 Mercury 90/65 jet. I bought it used from a dealer and have been pretty happy with the motor. I got it last summer and the first time I went to the river with it. I drained the battery trying to get it to start. Went back the next day and finally, it started up. After starting it, it ran like a top. If I cut it off, it fires right back up every time. All last summer through the fall, when I would go fishing, it would take a good 3-5 minutes of cranking on it to get it to start. Fast-forward to this spring, I take the boat out, drain the battery trying to get it to start. Went back the next day, still nothing, so I hit it with a shot of starter fluid, fires right up, runs like a top. Cranks up every time after that. I got home, cleaned the carbs, replaced the fuel pump and the enricher valve. I figured I would just replace all of the stuff that I knew effected getting fuel to the carbs. Went back out, same junk. Had to spray starter fluid to get it started. Now though, it's not cranking up as quickly after I've been running it. My bulb stays tight all day, and when I'm trying to start it I pump the bulb until its tight and it stays that way. I've replaced the plugs as well. I feel like I have to be missing something. I have fresh fuel in it and it still hard to start. I can't understand why it runs so good and cranks so good after running, but won't crank when cold. Any ideas would be super helpful. I've taken my kids to the boat ramp too many times to have to turn around and come home because the boat won't start!! Thanks.

 

[lckstckn2smknbrls]

If it's a 2 stroke motor you don't want to use starting fluid. It washes away any lubrication on the cylinder walls. Fill a small spray bottle with the appropriate gas oil mix to spray in the carb.

 

[turbotodd]

Does it have a real choke, or is it a prime start? Not familiar with that particular motor, but you're describing an issue that is related to cold engine fuel enrichment.

Prime start is just a valve that opens up a passageway in the carb. Lots of times the passageways are made of an air passage and a fuel passage down in the bowl somewhere. The passage in the bowl is usually tiny, and doesn't have a replaceable jet. They're so small that they tend to plug quickly and easily.

If it's got regular choke plates, have someone hit the choke while you look down the carb throats. The choke plates should close all the way. On the old school 2 stroke stuff with a mechanical choke in this style, it helps to advance the fast idle to near full throttle, hit the choke and then turn the key to start. Once the engine "pops", or attempts to start, let off the choke and then drop the throttle back to idle then attempt to restart. Should kick off.

If it's a prime start with no choke plate, advancing the throttle while cranking a cold engine makes it even harder to start. Just leave the throttle lever at idle and it should start if everything's working properly.

 

[JL8Jeff]

I had a late 90's Mercury 90 hp on my old 17' Wahoo and the day I went to look at it and try to start it, it fired briefly before stalling out, and then I flooded it and it wouldn't start again. I bought it anyway and I think the trick I used was to start cranking it before hitting the primer. It worked great that whole summer, I had to adjust the idle air screws to get a smooth idle but it ran great. My current 1994 Mercury 60/45 jet I flooded at the beginning of the season last year and it wouldn't start until I pulled the plugs and dried it out. I've been doing the same thing, start cranking before pushing in the key to prime it and it starts pretty easy. I wonder if you're flooding it.

 

[Webygail13]

I guess I could be flooding it. Not sure. It doesn't have choke plates, it just the enrichment passage. Are you saying that it's possible that the enrichment valve is working, but the fuel is not getting into the carb because that passage is clogged? I haven't thought about that. I've had several people tell me that it's probably my starting procedure, but I have found that hard to believe. I've tried different ways, but none seem any better than the other.

 

[turbotodd]

I guess I could be flooding it. Not sure. It doesn't have choke plates, it just the enrichment passage. Are you saying that it's possible that the enrichment valve is working, but the fuel is not getting into the carb because that passage is clogged? I haven't thought about that. I've had several people tell me that it's probably my starting procedure, but I have found that hard to believe. I've tried different ways, but none seem any better than the other.

Very possible. I haven't been into one of those motors, so I can't say for certain, but that sure is what it sounds like. If the system is working properly, no throttle should be used to start it cold. The enrichening system should take care of the fuel enrichment and additional air as well, throttling the motor any during cold start will make it harder to start.

 

[billyjoebigdaddy]

My two suggestions are simple but sometimes its all it is. The first is make sure your primer bulb is in a straight up and down position with the arrow pointing up. Most of them have gravity balls in them that will restrict fuel flow if in another position. Second is to check your fuel filter. Make sure you can blow through it easily and that its sealed in your fuel line and not allowing air to be sucked in...That's all I got