1994 Mercury Force 90HP idling/starting problems...

[Porima boater]

I bought a used 1994 Mercury Force 90HP outboard 2 years ago and last year the boat and motor ran beautifully. Never had 1 problem with it. Too it to a Mercury recommended dealer to be winterized. Stored inside a barn all winter. Got the boat summerized at the same location as winterization because they "guarantee" their work. Well I topped off the boat tank with new fuel and oil and dropped it into the water. It was running really sluggishly and didnt really want to idle. So I ran the boat at WOT for a while to make sure the new gas was mixing into the engine. I brought the boat home and the next couple of days I saw a small amount of really bad water oil mix coming from the lower uniting around the sked. I called the shop back and they stated that the mechanic that serviced my boat was no longer there and they could not confirm if there was water in the lower unit when they "serviced" it. They stated more than likely it was just a small amount of oil that ran down the casing that usually happens when boats are serviced with oil changes. I didnt think anything of it cause it was a such a small amount. Basically the size of the bottom of a drinking glass. I took the boat out to the same place about a week later and it was beginning to run worse. Brought the boat back in and very next day I had dinner plate size oil water mixture coming from the prop housing around where the last leak was from. Took the prop off and noticed that it was coming from the prop seals. Called the shop and they stated "They are a MerCruiser dealer and they are not an authorized mercury outboard dealer so they cannot guarantee any work on my outboard. They stated they are not liable for any problems with the boat because they performed 'normal winterization and summerization'. However they can refer me to a few places that can help me with any problem I might be having." Basically determined they didnt really do any work on it and might have messed up the outboard. Talked to one of the people they referenced and he stated it would be able 100-150 dollars in parts and about 600 in labor to replace the prop seals. I determined I would replace the seals myself with the repair manual that the previous owner used on the outboard with some youtube videos and replaced the driveshaft seal along with the prop seals at a fraction of the cost. Performed a few gear oil flushes to make sure everything was good and then a pressure/vacuum test. Both tests passed with flying colors for over 1.5 hours. Refilled with new premium gear oil and no leaks.

Replaced the spark plugs with new mercury recommended plugs and a new inline fuel filter. Took the boat back out in the water and the engine still wouldnt idle properly. Checked compression of all cylinders and have about 120# in each cylinder. The boat runs pretty good off the garden hose in the driveway. Only before it warms up it runs sluggishly as if it doesnt want to start and then when it does start it doesnt want to idle. In the water I have the same problems much worse. First into the water it wont want to start the first two attempts and then it gets warmed up and runs fine. I took it about a 1/2 mile away from the launch and park it to do some fishing. Attempt to restart and the motor refuses to tun over multiple times (approximately 20-25 times with breaks in between). When the motor does turn over, the only way to keep it running is to immediately increase the throttle to put the motor in gear. Once in gear it runs fine until getting close to idle. Once returned to idle the boat immediately died. Looking for some answers to my problem. Much appreciated.

 

[SkiDad]

i think that is simply a case of the idle being too low - it needs to be at around 1000-1100 in neutral on the water and about 700-800 in gear - any lower than 650 mine will usually stall. I'm not sure what shifter you have - but I always start mine at the first time with it in pulled out into neutral and forward to fast idle.

The idle adjustment is at the bottom of the timing tower - it's a flat head screw with a 7/16 lock nut on it. Loosen the lock nut and turn it clock wise until your idle is 1000-1100 while in neutral and then check to see what it is if you just put it in gear. Remember to tighten the lock nut before you take off anywhere - that is a lesson i learned well. If you idle was good before have you verified you get spark on all 3 cylinders ?

 

[Porima boater]

I have verified good spark in all cylinders. The only problem with adjusting the tach is that the boat didnt come with a tachometer so its rather difficult to tell the speed. Maybe I can rent a tachometer from auto zone and figure out how to test it that way. would the best option be to take the speed off the flywheel?

 

[Jiggz]

Invest in a tiny tach even for troubleshooting purposes only. Even those cheap knock off from *bay will do. Idling/starting problems are usually related to fuel delivery or with the carbs. You will need to dismount the carbs' bowl one at a time and clean the needles and ports and make sure the floats are not torn and working properly. Check to make sure the idle fuel air mixture screws are set at least one turn out from slightly seated. But before doing this, you need to unscrew it all the way out first and do an inspection. The pointed tip should be perfect in shape. Thread it all the way in but be very careful not to tighten it. Then back it out 1 full turn for initial setting. You will adjust this again later after you finally have it idling properly.

Do an inspection on the spark plugs. Note any sign of fouling or if being clean as a whistle. A very clean plug indicates either is it not firing or there is water intrusion into the cylinder thus steam cleaning it.

Try again and make sure you follow proper starting procedures.

As for winterization, basically none is required except to inspect the gear oil. You do not need to change it as long as you can verify it is not contaminated. If yours has a drain on the bottom, all you need to do is drain about a tablespoon and see if it is clear and bright. Since if there is water contamination it will surely settle at the bottom of the LU. Now if you do not have a bottom drain, then you will have to replace the oil before storage for winter. And the other thing for storage is to keep the motor on vertical position to keep it fully drained.

 

[Porima boater]

So I found an new-old 20 pole Tach on ebay that I will be getting in a few days so I will install that as soon as I can. I talked to a regional force technician and they also recommended while waiting for the tach to do a quick Dunk's Decarb method. He said that will help with the idling problems as well if the jets are gummed up in the carbs since I couldnt verify when the last time it was decarbed. He also recommended to do it anytime it was sluggish and/or after 50-100 run hours. He said to only put it slightly in gear and not to go anywhere close to WOT. The first two times of Decarbing it I got a ton of smoke that the neighbor called the fire department. Should have came out and talk to me instead. Anyways I was not able to finish decarbing it because I had to go to work and will resume in the morning, weather permitting. The first time was run was awful and barely got it to run. After the first run when it really started to smoke I was actually able to get a lot of the throttle control back. Previously I had to place the throttles to about 1/2-2/3 WOT in order to put the outboard in gear. During the second I just barely needed to go past the neutral interlock in order to see increase in RPMs and the outboard placed in gear.

 

[Jiggz]

Decarb'ing is a good practice as long as you are aware of its consequences. Decarb'ing reduces the lubrication in each cylinder and if not done properly can result in piston ring failures or piston failures. The best indication of high carbon is pre-ignition or detonation in the cylinder and also the spark plugs fouling. If the spark plugs are really fouled, clean them up and fix the problem before replacing them. Replacing fouled plugs without correcting the source of the fouling is like chasing one's tail.

You need to report on the status of setting the idle mixture screw and also on the condition of the spark plugs and of course the idling condition of the motor.

 

[Porima boater]

So I looked at the plugs and they were normal no fouling with some oil on them. I checked the idle mixture screws and they were already set at 1 turn open. I also completely removed them and checked the needle points and they were not fouled and were very pointy. Finished another round of decarbing and similar smoke event. This time the water that the exhaust was in was rather dark grey in color. I was running the outboard in a huge tub from walmart with a supply water hose running to it instead of the muffs. I got some reflective tape and a calibrated photo-tach from work which is calibrated to +/-1 rpm. While warm and idling it was reading about 680 rpm and when just barely in gear the rpms drop to around 550-575rpms with it sputtering and wanting to die in forward gear and not quite wanting to die in reverse. The FARIA 20 POLE 8K RPM BOAT TACHOMETER is expected to arrive monday possibly tuesday. So until that is installed it wont have a real good backup on my findings until then. I also did not have to go far past the neutral interlock for the motor to be put into gear this time. Any other thoughts/ideas is appreciated.

 

[Jiggz]

If your photo tach is accurate, the idle setting is too low for the motor to properly idle. 2- cycle engines are vicious when it comes to idling. They not only idle poorly but it is also detrimental in the long run due to accumulated unburned fuel in the crankshaft area. You can still use your photo tach and set the neutral idle to at least 900~1000 rpm and when in gear it should be around 750~850. Remember, when getting in gear, you should be a little snappy to get in gear and giving it a little gas while doing so. NEVER EASE IT IN that it causes grinding causing premature wear on the clutch dogs.

If you experienced grinding of the clutch dogs before it engages and the motor jerks a bit when placing in gear, that is an indication the idle rpm is a little too high. Re-set the idle speed but only low enough that it does not stall when placed in gear.

 

[Porima boater]

Thank you everyone for the help. I have to wait until the Faria tach comes in because I had to return the photo-tach back to work. I have a baseline value to compare the Faria tach when I install it and will make adjustments once that is installed. If not it will have to wait until next weekend when I go back to work to re-borrow the photo- tach again. I will also left everyone know of the outcome when the rest of the work is done. Tach install and raising idle setpoint.

 

[Porima boater]

Faria Tach installed and also confirmed that idle rpms was at low 500. Adjusted to 1000 or slightly lower rpms while in idle. Retested out on the lake and didnt have any stalling issues anymore. Starts right up everytime and goes into gear smoothly. The only thing I noticed is that my WOT is getting a max of approximately 2500 rpms. suggestions?

 

[Jiggz]

If you are only getting 2500 RPM at WOT speed, assuming the tach is accurate you definitely either have fuel related problems or your system is not "synchronized". These boats requires proper linkage adjustment so the control lever is in synch with the rest of the ignition system (trigger timing and advance) and fuel (carb) system. If you have not done so, read through the first three sticky posts on top of this forum. There is one in there that discusses "link & synch" to make sure that when your motor idles accordingly and responds properly to control lever positions.

Another thing that is also indispensable is installation of a clear fuel filter (G-2 type from W-mart for less than $5) between the fuel pump and the carbs' inlet. This is more for troubleshooting fuel related issues and as a secondary fuel filter (there is a primary filter on top of the fuel pump). When you start to experience slow downs at WOT or the engine bogging down, remove the top cowl and watch the clear fuel filter. If it stays full or at least 3/4 full, then you have carb problems (i.e., stuck needle, clogged inlet port or improperly set floats) or it could also be electrical due to misfiring. On the otherhand, if the clear filter empties then you have fuel delivery problem, i.e. faulty fuel pump, leaky fuel hoses, clogged or restricted pick up tube, faulty check valves on primer valve or closed or restricted tank vent.

 

[Porima boater]

Now here is something else that I just thought about, at WOT I am getting about 26 mph on my speedometer. I didnt think about using my phone GPS navitronics software to back up the reading. I remember last year checking the speedometer and it was reading the same if i remember correctly. Considering load is about average of 350 lbs of people weight + gear (mostly fishing gear, couple poles, tackle box, 2- 8lbs downriggers, 1-12 lbs anchor in the bow and a 20lbs weight in the aft, 1 tiny portapot and 1/2 tank of gas). What speed should I be seeing? I havent noticed much difference between loads when it is just myself (200lbs) and gear - portapot and 20lbs anchor to when it was fully loaded above. In fact I havent seen much speed difference from when I first bought 2 summers ago until now. This is also assuming the correct factory prop is installed as well.

If the engine is bogged down my top end speed should also be affected, correct? I have a 18' 1994 trophy 1802 Cuddy. not sure if that helps to estimate what approximate top end I should be seeing with a 90 HP outboard on calm small inland lake waters.

Could there also be a possibility that I have a 12pole outboard vice a 20 pole which I set the tach up as. I would think that setting the tach incorrectly would cause very odd readings, a few hundred rpms off..

I do have a clear in-line filter installed. So the next time I take the boat out I will surely take a look at it.

 

[Frank Acampora]

I am not sure because Mercury started making a lot of changes to Force engines around 1994 HOWEVER: If you have Mercury ignition and flywheel. then you do need a 12 pole tachometer. Easiest way to tell is this. The Mercury flywheel will be internally threaded in the center to accept a Mercury puller. Force flywheels will have three 1/4 X 20 bolt holes set about an inch out from the flywheel bolt.

 

[Jiggz]

If you are getting 26 MPH at WOT that means the engine is running fine and it is the tach (newly installed) that is incorrectly giving RPM. You can use that laser or photo tach you had earlier (be reminded you can get one of these from*bay for less than $15) to verify the accuracy of the new tach. Experiment with the settings and find out which one fits you motor.

 

[Porima boater]

Here is a picture of the top of the flywheel and just from an initial look it appears to be a force flywheel. Am I right?

 

[pnwboat]

That is the flywheel that is used on the Mercury style Switch Box ignition system from about 1992ish to about 1995ish. It should have six magnets glued underneath to the inner circumference of the flywheel. It has the three 1/4 X 20 bolts for a puller. It requires a 12 pole tachometer, which are more readily available than the older 20 pole tachs.

From 1996 on, the flywheels had a larger hole in the center to accommodate a larger diameter crankshaft snout, and added an internally threaded lip around the center hole.

Here are some pictures of the 1996 and later 3 and 4 cylinder motor flywheel top and bottom that use the Mercury CDM ignition system.


Here are some pictures of the 1992ish - 1995ish 3, 4 and 5 cylinder motor flywheel top and bottom that use the Mercury Switch Box ignition system.


Here are some pictures of the 1991ish and earlier 3, 4 and 5 cylinder motors flywheel top and that used the Prestolite ignition system.


System will not let me post more that 5 pictures, but the Prestolite system flywheel has a single strip magnet that runs the entire inner circumference of the flywheel instead of the six separate magnets like the later years.

 

[Frank Acampora]

That is a Mercury flywheel. Quite frankly (Most times I am Frank LOL) I forgot about the three tapped holes in the Mercury flywheel--see: Merc used a couple of different flywheels. At any rate, that flywheel should have six magnets underneath and the ignition should use a 12 pole tachometer.

 

[Porima boater]

Well then.. that would be my flywheel. I did look underneath and there was 6 magnets there. So looks like I just need to change my tach from 20 pole to 12 pole setting. I find that a little odd that the tach was still accurate at 500 RPMs when it was on the 20 pole setting. Guess I will have to change the tach to make sure that the idling is still set correctly and also recheck my RPMs at WOT again.

This would have been much easier if I was able to read the serial number for the outboard. Is there anywhere else besides the sticker on the transom mounts which the serial number might be written?


So would a 20 pole flywheel have 10 magnets or is that a different concept?

 

[Jiggz]

No, the prestolite flywheel that uses a 20 pole tach instead has a single strip of magnet around the flywheel's inner vice 6 strips as shown. As for the serial number, unfortunately, nowhere in the engine or any part of the motor is it written except for the lame cheap sticker on the left transom. However, if you still have the sticker you might get a chance to read it using different light colors, i.e. UV lights. Although, generally all you need to know is the model of the engine and you should still be able to order parts accordingly.

 

[Porima boater]

I adjusted the tach to a 12 pol setting and started it up on muffs. It wanted to run away of the muffs. on the 12 pole setting it was reading 1600 at idle so I adjusted it back down to 1000. I also am a little concerned about the water pump. I dont believe I am getting the amount of water out of the upper ports as I should be getting. It wasnt a nice steady flow. it was more like stop and go spurts. Anyone got a good video link on how much water should be coming out of the upper ports while on muffs for this motor?