100 hp mariner late 80's early 90's 4cylinder 2 not running

16.5 Lund tyee 4.9 (44mph2person) 5100rpm

Problem I have is it takes 15 to 45 minutes sometimes before I can get the other 2 cylinders to kick in then it's good for rest of the day.( After 1800 rpm all 4 cylinders fire). Things I have tried carbs cleaned with chem-dip and replaced carbs and linkage, plugs changed and hotter, fuel pump and vacuum hoses cleaned or replaced, ran premixed gas and oil, timing*+ and -

I am new (3 years on the water) to outboards but am learning could use some direction here please.

Are theses things possibly stopping the lower 2 cylinders from firing???
*
Thermostats see i have 2 (143) and (120) could they be sticking causing problem.

Next I think I have a 19 pitch prop would 18 give me more rpm there for make the other 2 cylinders fire more easy cuz less drag ( it runs at 5100 rpm now witch is close to accurate I think old tachometer and sticks slightly at 3200rpm.*

Last is my reeds are sticking then work fine for rest of day??

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

What is the s/n of your engine?

Gerry

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

a smaller pitch will give you more RPMs from 5100 with the 19 P to about 5500 with the 18 P depending on weight and cargo as well as passengers. See what the manual says the top RPM should be and try to shoot for that to relieve stress on the engine. I don,t think it will help the lower 2 cylinders. Check compression on all cylinders and they should be above 100 Psi minimum. There should not be more than a 15 Psi difference from any of the other cylinders. Some of the newer engine have a feature that it runs on just some of the cylinders until there needed and kick in. I don,t know weather your engine uses this feature. Bad reeds will not seal under low RPms but will seal with more suction during higher rpms. I know this isn,t much help but just some info that might be useful in doing research. Carburation is something that could be causing the problem as well. readjustment may help and if it the lower carb is getting gas in the throat when priming with the bulb then float adjustment may have to be made. Check to see the engine charging system is working properly and that Like mine did today over charged and burnt out the switchbox. I had a spare rectifier (Correct one and another switchbox). Make sure all coils ar good and grounded properly. Check all plug wire leads for cracks and arching (Best done at night running to see sparking). If I can think of anything eles I,ll edit to this post

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

Troubleshooting in a methodical manner will quickly narrow your focus to solve the problem.

Start with a simple compression tes, then a spark test of each plug wire using an adjustable gap spark tester set to 7/16 inch. Consistant compression readings and a hot blue spark can rule out obvious mechanical problems and ensure the ignition is operating well.

After that it is all fuel and adjustment.

If you know your way around a carb, look closely and see if the lower two carbs have idle mixture screws.

Since the late 80's Merc/Mariner has a 2 + 2 series 4 cyl's, they only have idle mixture screws on the top two carbs, the lower two carbs only pass enough fuel mix for lubrication, not enough to support combustion at lower engine RPM.

Carb sync, timing, accelerator pump, all are a delicate balance and once dialed in perfectly following the FACTORY Service Manual many operators cannot tell when the motor is running on two or 4 cyls.

Chaeck compression, check spark, see if the lower carbs have idle screws, then repost and let us know what you have.

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

Since the late 80's Merc/Mariner has a 2 + 2 series 4 cyl's, they only have idle mixture screws on the top two carbs, the lower two carbs only pass enough fuel mix for lubrication, not enough to support combustion at lower engine RPM (under1800 rpm)

Yes this is my setup I have replaced all 4 carbs and rebuilt super clean with linkage and fuel pump. spark tested wires good(have not compression tested )

The engine lags dogs for 15 to 45 min no mater the weather cold or hot / water temp, then bang kicks in good for the day I can let it sit 6 or 7 hrs still fine but give it a 12hrs rest back to 15 to 45 min before it takes off again( that dont sound like compression?

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

Again, what is your s/n as I might have the manual for it?

Gerry

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

I can't find a S/N but its one of these 0A722297 THRU 0D283221 or 9523034 THRU 9793576 they look the same to me cant find a difference. I looked for the S/N# was not there...Also looked on the block somewhere was the other way to the S/N but that failed also.............

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

I can't find a S/N but its one of these 0A722297 THRU 0D283221 or 9523034 THRU 9793576 they look the same to me cant find a difference. I looked for the S/N# was not there...Also looked on the block somewhere was the other way to the S/N but that failed also.............

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

Those s/n ranges you provided are between 1987 and 1993 which is pretty broad. Anything in that range should have a disc like this on the powerhead:

http://imageshack.us/a/img84/8224/391496208.jpg

Gerry

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

Ok THANKS I will look for that disc tomorrow working all day today. But all them engines from that range are basically the same design.*

Getting the bottom 2 cylinders to fire is the trick and I think the only person who can answer this is a person who had this motor and problem. I have read the post of people who have posted the same problem. Never found answer yet, one post it was the carbs, but I did replace them, rebuild, also chem-dip them supper clean.

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

Your engine should have spark on all 4 cyls all the time, it drops the 2 cyls at idle from a lean cond not loss of spark. If it losses spark(fire) then the low speed winding in the stator is not working properly.

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

Hmmm sounds good but think you mean high-speed (YES ALL 4 FIRE EXCELLENT ) But if all 4 fire how could it be the stator /// stator stops working then starts working for 3 boating seasons. Would it not burn its self out being electrical and all, or could that happen. The engine rips on the garden hose.. Thinking tied engine 19 P is to much maybe 18 P would help it get into the power power-band.

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

Compression tester also needed this weekend.




Thanks everone for putting stuff out thier for this motor.

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

Thanks for the help, ****

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

i find it hard to belive that you are running your motor for sometimes 45 min and you havent seized the two lower pistons think about this if you have spark the only thing that would prevent them from firing is lack of fuel that means that you just ran your lower two cylinders in a lean state for 45 min and all of a sudden they start firing and everything is fine would never happen those two cylinders would be burnt up by then ... what makes you think that they are not firing ,how do you know its the two lower cylinders not firing,how do you know cylinder # 2 is firing ,how do you know cylinder #1 is firing .. i belive you will find an electrical issue somewhere that is where i would look, also have you ruled out water entering the powerhead somewhere run the motor then shut it down .pull the spark plugs out look for signs of water water dropplets on plugs , milky residue on plugs etc

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

If water intrusion (Usually the lowest cylinder or cylinders) is happening the plugs would be white not browm from steam cleaning. If black too rich, to much oil mix, or leaking reed, or intake valve, leaking head oring, cracked head, etc etc.. Check the plugs for this. Lower reeds, carb adjustments, bad wires, or coil, trigger, and swithbox are all candidates for non firing plugs when they should be. Bad points pick up etc etc. Use a manual to trouble shoot because this is no more than a guessing shooting gallery

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

Bad switchbox or sticking injectors my $.02. Reasoning being stator cannot only fire 2 cylinders and the injectors stuck or clogged will not allow accelerator pump fuel shot into cylinders

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

Faztbullet said:

Bad switchbox or sticking injectors my $.02. Reasoning being stator cannot only fire 2 cylinders and the injectors stuck or clogged will not allow accelerator pump fuel shot into cylinders

Click to expand...

Ditto, disconnect throttle cable, pull the hose froom the accel pump, open throttle while watching hoses to see if fuel is pumped out. Then remove injectors for cleaning. Repeat test thru injectors to check pump/spray shot.

You didn't mention RPM range that this problem happens, just off idle, mid-range, hole shot?

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

Ok its has 4 carburetors no fuel injector I am 100% sure fuel system works perfectly, sure they get some fuel to lubricate but just don’t fire till some kind of vacuum at 1800 rpm I was told.
Switch box would not work for 3 years only when I am first on the water for 15min to 45 (can a switchbox stick?)

Thinking my 19 prop is to much drag and I cant vacuum up…. 16.6 Lund aluminum ,4 seats, walkthrough ,live well full 30gal ,large aluminum built in gas tank 25gal?or so Always full, trolling motor , extra large battery, always lots or gear. 8hp kicker motor, I rebuilt the floors with ? plywood coated 7x in outdoor polyurethane heavy plastic wood. 3 to 5 people ever time out. Boat with load 2500lbs + thinking 17 in prop am I wrong in thinking that.

Re: 100 hp mariner late 80's early 90's 4cylinder 2 not running

Throttle linkage should have a cam the presses a plunger into a body that has fuel hoses on it. This is the accelerator pump with hoses feeding the injectors mounted into the side of the engine block squirting into the lower cyls. The injectors are hidden under the electrics panel on the Port side of the motor.

Proper volume, timing, and spray of the injector system is critical in getting a combustible mixture at the transition RPM range, somewhere in the range 1500.

These 2 + 2 motor once dialed in run seamless, many owners cannot tell the difference when the motor is running on 2 or 4 cyls.

I LOVED mine, idled and trolled all day, could 'bump' the throttle and increase RPM a couple hundred at a time, and with the vented 23P prop screamed outta the hole and dashed my 185 ProCraft F&S to 44 GPS. Not bad for my fat ***** all my stuff, and only a 115 Merc/Mariner.