1998 mercury bog foot 50elpt died after a long day on the water

[wheelers4life]

I bought this boat and used it three times, ran great I thought except the rpms at wot are around 4k with 4 people on board the pontoon. Then around 4 pm it started rough and if I gave it any throttle it just died and woudl not start. I took it home and pulled the plugs they were black. I put brand new plugs in the outboard and took it out. Ran just fine. today I took it out and it ran fine today untill 4 pm and then same problem. came home and took plugs out and they are all 4 black. Can anyone give me any help on this issue.

 

[dawwgman]

Check for rich fuel mixture. Is the plug oily if so then check fuel mixture.

 

[merc850]

Check the factory rpm ratings - 4,000 seems a little low for full throttle this could be the reason for plug fouling, you might have to buy a lower pitch prop to put it in the range.

 

[wheelers4life]

Ok this morning I purchased a spot fire 13.8 c 10. Prop. This is the recommendation from the mercury web site. I did buy a compression tester. Tested all 4 cylinder after running the outboard for 15 min. For some reason I'm getting 60 psi on all 4. I even squirted oil in the spark plug hole. No change in psi. Could this be an anomaly. Or did I buy a junk 4 stroke with this boat.

 

[wheelers4life]

The outboard is not hard to start. Runs at 15 mph website says 16.2mph at wot for this boat.

 

[wheelers4life]

I know it's weird that all 4 would be low and the same. Unless maybe fuel is getting onvthe cylinders and washing out the readings

 

[Silvertip]

It is not uncommon for compression test gauges to be inaccurate. Try another gauge. But black plugs do not get that way from idle fuel mixture. If this is indeed a four stroke, is the engine carbureted or fuel injected? If fuel injected, the pressure regulator diaphragm may have ruptured and flooding the engine with fuel. Pull the dipstick and smell it. If the oil level is high and or you smell gasoline, do not run the motor as the oil is contaminated with fuel. Replace the regulator; If the engine is carbureted a hung or misadjusted float or sticky needle & seat in the carb may be the cause and a carbs therefore need to be rebuilt. If carbureted, the primer/choke system may be dumping excess fuel into the intake.

 

[wheelers4life]

It is carbureted I will take this compression tester back and purchase another one tomorrow. I have checked the oil. Looks and smells good. I will look into pulling the carbs off when my synchronizer comes in.

 

[wheelers4life]

Ok new compression tester and all 4 are at 120 psi

 

[Texasmark]

Check the factory rpm ratings - 4,000 seems a little low for full throttle this could be the reason for plug fouling, you might have to buy a lower pitch prop to put it in the range.

+1. Check this out: https://boatspecs.iboats.com/Mercury...8/bpe/57e16387

Something is dreadfully wrong. You are 2k rpm low. If your compression checks good and you are running the right prop and your fuel is fresh and clean (4 stroke you said meaning you don't mix oil with your fuel) and it's easy to start (an indication in itself of good compression) then something else is the problem.

You mentioned that it's a "toon". In what kind of condition are the tubes....the part riding in the water? Are they nice, clean aluminum, or are they caked with barnacles or slime or moss or things of that nature. Takes very little of these things to really whack your performance. If so, till you get them cleaned back up, nice and shiny, don't expect miracles from your engine.

If dirty tubes is the problem, after you get them squared away, get some Sea Foam (any auto parts store) and Google "DeCarb" to clean up your engine....don't forget to change the spark plugs after the DeCarb process. Then I'd use it per instructions on the can regularly in your fuel to keep your engine squeaky clean.

 

[wheelers4life]

I found out that the prop on the outboard was not the right prop. My local tracker dealer or9me the right prop. The on I have now is silas 14x14 4 blade. The new one on order is a 13.8x 10 spitfire 4 blade. The toons are in great shape. I did do a decarb yesterday after I did my compression test, just to clean it out. I used one can of seafoam in one gallon of fresh gas. 15 min runtime 15 min sit time until all was gone. I do think the outboard is way low. I can bring it up 3 to 4 inches if necessary. I am waiting on the new prop to come in before I do anything else.

 

[wheelers4life]

Ok today it lasted about an hour on the lake and it died. Now it very hard to start. When it does start I have to give it full throttle out the gate or it dies and wont start. It will idle if I let it sit for about an hour but if I give it just a little throttle is sputters and dies. The takes about 10 minutes to get started. After that I hit it full throttle and she will run until I let off and it dies again

 

[Texasmark]

First off where are you rpms now? Then, if reasonable, aka within the recommended rpm range at least, time to go through your fuel system. A quick test to determine it's fuel is to take a can of Aerosol Sea Foam with you next time you are out. Remove the cowling and any plastic coverings (air shroud) over the carburetor intakes so that you can look directly into them. Go through your routine and the minute it tries to die, give your carb(s) a shot of SF. If the engine immediately responds with an RPM increase you aren't getting enough fuel.

One of your problems may be pieces of fuel line getting into the fuel channel and winding up in the carb(s) blocking your high speed jet for one thing. On my last engine, at 10 years old, running E10 I had carb problems and found such in 2 of my 3 carbs. One piece was wedged down in the high speed jet which is at the bottom of the carb. bowl and I didn't see it till I applied compressed air, after thorough cleaning and dislodged it.......it was my main issue.

New internal fuel lines and fuel filter (get the flow arrow in the right direction), new fuel line from that tank to the engine, new Merc. OEM squeeze bulb, flushing the tank and strainer in the input of the fuel line in the tank, new fuel pump diaphragm.....anything rubber in the fuel system change it. At 1998 you are wayyyyyy overdue for new rubber. My engine was a 2002 and the problem occurred in the 2012 time line.

 

[wheelers4life]

I dropped it off at a shop.

 

[Texasmark]

Keep us posted on the results and your test drive results. Wink!

 

[wheelers4life]

They just called and told me they cannot find an8 wrong with it. I explained what it was doing and they said they will run a few more test. This is frustrating

 

[QBhoy]

Sounds like a fuel issue perhaps. Can you get a video ?

 

[wheelers4life]

Ok just got the boat back. They said they checked the fuel pump, coils, spark plugs, fuel filter, timing, and drained the fuel bowls on the carbs, the bowls looked good and clean. I just installed my new prop going to test it out if the wind gets below 25. They could not reproduce any problems and compression was 120 for all 4 cylinders. They do not have a carb synchronizer so they did not pull the carbs. I thought that was a little sketchy. At least they did not charge me anything

 

[racerone]

Any pictures of this 1998 model 4 cylinder motor ?----Post the serial # as well.

 

[wheelers4life]

My phones pictures are to big