50hp 4-stroke mercury problem

Hey Guys, I have a 1997 Merc 4-stroke 50 hp tiller motor and while out fishing this past weekend, I hit some rough water (not sure if this even has anything to do with it) but was going full speed hit the waves then I reduced the speed, until calmer water. I then went to give it full throttle again only to have the motor bog way down. Runs great at idle, starting, and up to now 8mph and thats it after 8mph it will go between that and 8.7 mph and just boggy no power and doesn’t go. Any ideas? I was just goint to bring it to the local shop for them to look at it, however they are 6 weeks out on service. Help needed here for I have the Pooh Bear Tourney on June 2nd.

THANKS

Is your 97 carbed or fuel injected? If it is carbed I would be willing to guess that your high speed jet is plugged causing the poor / non-existant above idle performance.

What James said is a possibility, at the same time its a strange coincidence that it happened instantly.

Its not impossible something came lose in the throttle assembly, either that or a fuel pump went out.. it cant get gas quick enough to support higher speeds?

I guess I would get a manual and go through the trouble shooting. have a hard time believing a jet plugged instantly, however, it is the right symptoms of a high speed jet. A weak coil can also give this kind of problem… even a bad plug/plug wire.

It sounds to me like something jarred lose.

I’ve actually seen this happen a pair of times after an impact. I assume that in both instances the carb was in need of a cleaning but still getting by and the impact shook some crub loose, plugging the jets suddenly.

Normally it is the low speed jets that get plugged first due to their finer diameter but it might be worth a look. If you have basic tools and a little “wrench-ability” it is an easy fix.

If it is fuel injected… I’m of no help.

I have that same motor/same year and I had an issue very similiar and started pulling plug wires as it was running and found a corroded plug wire. Since new wires are very expensive I just cleaned up the bad one and life has been good ever since…RR

I had the same problem with an older Evinrude 50. It ended up being an air leak on the hose connection to the fuel tank. Hope this helps. It’s an easy fix.

Thanks for the input so far guys. I do know how to manage some minor motor work, however carb work is delicate. lol I will try the plugs for thats the easiest step. As for your answer James it is a carbed 4 stroke, so I appreciate your input, however if it is the carb I am going to have to find a dealer or somebody in the White Bear Lake/Somerset Wisconsin area who actually can do a quick fix and check of the jets, for fear of messing some setting up on the carb during cleaning. Step #1 I guess will be the spark plugs. I appreciate everybody’s input

One more thing you might look at. Mercury used to have a throttle control that connected the carbs that has a universal black nylon ball joint that has been known to pop out of the nylon socket. When this happens your motor will start and idle just fine and even accelerate to a point before it bogs down. Then it sounds as if it is running on half the cylinders until you throttle down. They used this ball joint design on some of their older carbed 4 strokes and 2 strokes.

That is a concern as well. When I tried to pump more fuel to it by using the inline ball pump thing it wasn’t full of fuel and when I pumped the ball it didn’t seem to help any as well. Looks like I have alot of trouble shooting to do.

EYE HUNTER that sounds exactly like the problem. The rest of the day I was fine trolling at 2.0 – 2.8 mph. Sounded perfect and ran perfect, but when I went to accelerate up to 8mph it would be perfect until a certain point and all of a sudden bog way down and would feel like it wasn’t running on all cylinders. The first thing I checked were the spark plugs and see if the caps were on all of them. Seemed like there were all good, but might as well replace them and try to figure out the location of this nylon ball/socket/nut thing your talking about. Any idea of the approximate location or what would be attached to it?

EYEHUNTER one more question. Do you think this would need to be replaced or can I just place it back into the socket?

BH24
If you’re looking for someone GOOD in the White Bear area who can get you in quicker than the dealerships, TRY HOSS. He’s two doors south of Nelson Marine.

Whats the name of his place? HOSS? what does that stand for?

HOSS Performance
3696 Scheuneman Road,
Saint Paul (White Bear?, Gem Lake?), MN
55110

phone: (651) 653-3507

I’ve been happy with the work he did for me. I was looking for service late last fall when Nelson’s was busy winterizing boats and they actually recommended him.

Should be on the side of the motor where the throttle linkage hooks up to the carbs if you have one on your motor. If you find the ball popped out of the socket you can try to pop it back in. I ended up having to replace the one on mine but it wasn’t a big deal. Hope it turns out to be something simple like the ball joint.

Eyehunter

I have a 90 2001 Merc four stroke engine. In those years Merc built the lower unit and Yamaha built the power head. I am on my 8th season of use (I bought the motor in the month of August in 2000), and I have never had this problem. I took this motor into my dealers this spring because I thought it should be looked over for some minor adjustments. This is because this motor has never been in for anything except oil change, and lower unit change. I was told that this carb motor has had problems like you stated but because I entered a can of Sea Foam every other tank full I was o.k. With this motor or any other I would suggest to put in Sea Foam and burn high octane gas or non oxgygenate gas when ever possibe. Bottom line is that a penny of prevention means that a pound of relief will not happen! Trust me! By the way, I love my Merc four stroke!

I just picked my boat up and believe it or not it was just one bad plug. Unreal, and I wish I wouldn’ve just changed the plugs before bringing it in but didn’t want to use up the extra time and not have that be the problem. I was worried that if it was something else that I wouldn’t get the boat back in time for the Pooh Bear tourney. All good they said they went and tested it and it ran great 6000 rpms oh yea..can’t wait to get it on the water myself. Thanks everybody for your input.

and you blamed your lack of speed cause of me

After paying over 6 hundred dollars, I still have the same problem
After traveling full speed across the lake 4 miles it will miss when trolling around 1200rpm and up yet if I turn the motor off and jig for half hour and start the motor it will then troll without a miss. When I travel back to dock at full speed the throttle down to troll into position it will start to miss again.. running out of money trying to fix at this dealer.

carl connors wrote:

After paying over 6 hundred dollars, I still have the same problem
After traveling full speed across the lake 4 miles it will miss when trolling around 1200rpm and up yet if I turn the motor off and jig for half hour and start the motor it will then troll without a miss. When I travel back to dock at full speed the throttle down to troll into position it will start to miss again.. running out of money trying to fix at this dealer.

OK, you’ve jumped into an 11 year old thread, expecting us to know your situation. It almost sounds like a heat-related problem, when the motor is run hard, then the problem develops. What has been replaced so far?

HRG

They replaced the mapping whatever that is and second time they told me I ran it in trolling to condition to much and needed to run faster longer
my Brother in law has same issue with same motor

Put a new hose and bulb and a bit of Seafoam worked for me with the same situation