90hp Merc Power Loss

[efdog]

Ok, so I have a 1997 Mercury 90 hp 2 stroke oil injected. I bought this last fall and am somewhat unsure of the history or maintenance practices by the previous owner. It was used on 2 outings last fall without issues before being stored for approx 6 months (stored with a full tank and marine stabil). I ran it on muffs a couple of times in between. I got it into the river for the first time and it ran for about 5 minutes before the rpms would drop from 5000-5500 to about 1500-2000 rpms in 1-2 second spurts 1000 rpms at a time. Even at an idle the motor wasn't sounding quite right. Gargling a bit?? I was able to get back to the dock at low rpms, but any attempts at WOT will quickly drop off. A visual at the fuel lines looks good (no obvious cracks or leaks). The primer bulb does not firm up the way I'm used to, but I can feel the fuel moving through...I then unhooked the fuel line from the engine and gave it a few pumps then re-attached. After this I decided to give it another go and everything seemed fine. Topped out at 5500 rpm's all day long. I ran it again the next weekend for 2 days straight, now just assuming it must have had bad fuel that sat in the fuel lines. A week later after cruising around for over an hour at 4000 rpm's, it happened again. This time I'm out on choppy water. Again the engine doesnt sound quite right. Idling normal and not really labouring, but almost sounded like gargling. For whatever reason, my trim decided to start acting up and is trying to trim down???? I have no idea if or how the 2 things could be connected, but I'm mentioning it anyway (I've never had any issues with the power tilt/trim). So I disconnect the battery to stop the trim, disconnect the fuel line, prime it a couple of times, then reconnect the battery (trim is now done acting up), and then reconnect the fuel line. Start it up. Sounds great, runs great. I take the hour + trip back to the marina with no issues. ..and that's where I stand now. There's a problem, and I have no idea where to start looking. Hoping someone can point me in the right direction, before I start spending...I have a solec manual that wasnt much of a help in diagnosing the problem.

 

[efdog]

Re: 90hp Merc Power Loss

Upon checking my plugs, noticed the top plug wire was loose. When I went to pull the boot off the plug, the opposite end of the wire pulled off as well. If the top plug was not performing consistently, could this be my problem?

 

[Superjetjim]

Re: 90hp Merc Power Loss

It certainly wouldn't help matters... Might be worth pulling your carbs to check the jet are clear. Also you may have some debris sloshing around in the tank and randomly blocking the pick up - not uncommon..

Jim

 

[sxmerc]

Re: 90hp Merc Power Loss

As far as your trim acting up, depending on which control box you are using, you may have two wires shorting together. If the box has been used for awhile, all the movement of the handle can cause chaffing of the trim switch wires. If it acts up again, that's where I would start looking.

 

[efdog]

Re: 90hp Merc Power Loss

Thanks for the reply. Pulling the carbs will be something I'll let my MM do. How can I tell if there's debris in the tank? Is there an additive I can use? My tank is completely enclosed in the hull, so a visual inspection is a no go. In fact I'm having trouble checking the fuel lines that are in the hull as well. There's absolutely no gas smell in there, so that makes me assume there's no leaks. I've assumed before though!

What kind of damage could I be doing by running it with this intermittent problem? I certainly do not want to further the problem, but I have a feeling my Mechanic will find nothing wrong since it's only happened twice in approx 10-12 running hours.

 

[efdog]

Re: 90hp Merc Power Loss

Trim:

I use both control boxes (motor / throttle). I'll have a look at the throttle box today since it gets the most use.

Thanks!

 

[efdog]

Re: 90hp Merc Power Loss

I just got my boat back from the shop dishing out a cool $700 bones! They changed the inline fuel filter. Checked out all the fuel lines. Swapped out the plugs. Noticed a bolt was missing and they decided to open er up to. Discovered a faulty gasket and a water to spray in there, that "would certainly" be causing me to lose power at WOT ...Long story short, I got the boat back into the water, and still the same problem, only now I cannot get over 3000 RPM's ever without a complete bog down. RPM's drop off and stalls. After 2-3 minutes I can restart and put slowly back to the dock. Oh yeah, compression was good on all 3 cylinders. Shouldn't the mechanic have checked the carbs before tearing into the cylinders for a 3 hour job?
I thought it was odd when I dropped the boat off this morning when the marine mechanic also asked me if I thought it was fuel related or electrical related?? WTF!!

Hopefully my findings will be able to help someone else here. I'll keep you posted!

 

[sxmerc]

Re: 90hp Merc Power Loss

Sounds to me like you need to find a better mechanic. Maybe at least one that's going to take the thing for a ride before handing you a bill and telling you you're all set.

 

[efdog]

Re: 90hp Merc Power Loss

I agree, however there's no other mechanics in my area that I'm aware of...so in 2 - 3 weeks I should know if a carb cleaning fixes my problem. For an experienced mechanic, how long should it take to completely dismantle and clean out the carbs?

 

[sxmerc]

Re: 90hp Merc Power Loss

I guess it depends on how they charge. Unfortunately, every shop is different. If I had your motor at my shop, I would be billing you for 3 to 4 hours to dissassemble, soak and clean, reassemble with kits, install, sync and link, and sea trial, plus parts. The carbs on this motor are quite simple, with not many internal parts. Some shops may charge more, some less. I run my shop with the knowledge that I depend on the customer more than they depend on me. There is always "someone else" to take the product to for repairs It's pretty simple. If you do good work at a fair price, the customer will come back, and more importantly, they will recommend you to friends. There is no dollar figure for word of mouth advertising... especially when it's bad word of mouth. Good luck with this.

 

[efdog]

Re: 90hp Merc Power Loss

Hey, thanks sxmerc for the advice. You're right with word of mouth. I actually got my boat back quickly this time, after expressing my displeasure. Carbs were cleaned, although was told they looked good and probably didn't need it. The problem was my fuel pump. New pump kit and I'm finally golden!! Working great now! I was charged another $200 for the cleaning of the carbs and the pump kit including labour. Seems reasonable. Actually sounding much better than before the problem started. Hopefully I didn't damage anything running the engine with a bad pump.
I have one question that's unrelated to this thread, however figured I would ask here anyway. When I pulled my boat out and trimmed my motor while trailered, I noticed some play in the lower mount bracket that wasn't there before. I'll post a picture, as I'm not sure exactly what it's for, or how to describe it correctly, and if it's actually normal for a small amount of play...seems like perhaps a seal is missing?

Thanks once again for your help!!

 

[efdog]

Re: 90hp Merc Power Loss

As mentioned above

 

[sxmerc]

Re: 90hp Merc Power Loss

Looks as though the lower bushing in the swivel tube is worn out. Fairly common on motors that have some time on them. While the part itself is pretty cheap, the labor required to get to it is not. I would just leave well enough alone, and just keep the swivel tube well greased. Probably not worth spending the money to replace this given the age of the motor. If it were mine, I would continue to use it.

 

[efdog]

Re: 90hp Merc Power Loss

Probably not worth spending the money to replace this given the age of the motor.

Good enough. As long as I'm not damaging anything. I'll lube that sucker up...Gee whiz in Atlantic Canada, a '97 motor is pretty darn new...with only 3 months a year of good boating weather, it's almost like a 4 year old. Too bad they basically have to be woken up annually. haha