Merc 150 problems

" I have a 1984 Mercury 150 w/

" I have a 1984 Mercury 150 w/ Oil Injection. I purchased the boat and engine late September last year. The engine ran well. At the end of the season however, it began to get increasingly difficult to start the engine. Once started, it did not run well at idle and often stalled out. I changed the plugs to winterize it and it seemed fine.

Unfortunately, the problem has popped up again this Spring. The engine is hard to start and stalls at true idle. Also runs rough at or below 1100 RPM. Stalls out when shifting through true idle. I have also noticed alot of smoke coming from the exhaust ports and Im not sure if this is just because of the age of the engine. But, seems to run well above 1500 RPM with no missing. Needless to say this is causing alot of headaches.

I have checked the spark plugs and they look ok. The fuel mixture was treated before the engine was stored. There is plenty of oil in the system. The water pump is working.

Any ideas as to what it could be? I would like to get this fixed before the heart of the fishing season hits! "

" Steve, this may sound too si

" Steve, this may sound too simple but I had a similar problem with my 175 a couple of years ago. My engine would run oil rich, sometimes stall at idle, etc, etc. Turns out the primer bulb was at fault. It was a new, but aftermarket bulb and the check valve wasn't closing completely, thus allowing fuel to lose it's prime. It was fine off idle but at low revs it wasn't happy at all.I would've never believed it since the bulb on the boat was new but as soon as I bought a new Quicksliver bulb the problem went away. Man, did I feel dumb. Hope you don't rebuild the fuel pump, go through the plugs, etc, etc, like I did. Try the $10 bulb first. Good luck, Bill "

Thanks Bill- I will certainly

Thanks Bill- I will certainly give that a shot before any other expensive work.

"Steve,

A number of things

"Steve,

A number of things can cause your problem. I would say the most likely causes are:

1. Clogged idle jet(s) or idle passages.
2. Flooding carburettor(s).
3. Malfunctioning stator.

When you squeeze the primer, you should feel it firm up when the float chambers are full. If a float is stuck or the valve is sticking, you will feel that the primer continues to pump fuel through the carb and will see it coming out the vent or even up through the main nozzle when you look into the carb bore. You have to remove the front cover to see into the carb bore. This would be flooding which can also be caused if the choke is stuck or malfunctioning.

In order to check the idle jets and passages you have to remove the carbs and carefully inspect everything.

The stator provides voltage for the charging system and for the switchboxes. If you look at the switchboxes you will see a blue wire and a red wire to each one from the stator. One set will have a white stripe. The blue wire provides voltage at low rpms and the red wire is for high rpms. Because of this arrangement it is possible not to have spark at at idle, yet have good spark at speed. You can use an ordinary voltmeter to see if there is any voltage here, even though you won't get a true reading. Touch the red test lead to the wire you are testing and the black lead to ground. You should get a reading on the DC volts scale while cranking the engine. If you get zero voltage on any of these wires the stator needs to be replaced.

"

"Steve, first do a compression

"Steve, first do a compression and spark ck, before you do ANY repairs at all. But, it sounds like to me, that you do have a fuel related problem, possibly plugged idle jets or air bleeds

Daren

"

" Tried the new primer bulb an

" Tried the new primer bulb and the engine ran fine at true idle until it suddenly quit. Checked the primer ball and it had completely collapsed with no fuel in the lines. Now I am not getting any fuel in the lines no matter how long I pump the primer ball. I have plenty of fuel in the tank. Will check the fuel/water filter to see if the gas is reaching that point. Man its great to own a boat "

"Steve....Mercurys are not my

"Steve....Mercurys are not my line of expertise, however your last message is a familiar one that might be listed pertaining to any boat with a built in fuel tank. Check the fitting at your tank where the rubber fuel line attaches. That may be (and most likely is) a sticking "Anti Siphon Valve". Remove that fitting. If it contains a spring, ball, and ball seat... knock out those items which will convert the anti siphon valve to a straight through fitting. The flattened out primer bulb proves that there is a restriction between the bulb and the fuel supply, and the most likely (common) problem, assuming the bulb itself is okay, is that valve.

Joe"

Dropped the boat off this morn

Dropped the boat off this morning at my local Merc Dealer.

I just don't have enough time to troubleshoot and fix the problem. Appreciate all the tips though. At least I have an idea of what some of the causes may be. I will post the outcome after the engine has been serviced. Hopefully it will help someone else that may have the same engine problems.

" I have a 1979 175 Mercury en

" I have a 1979 175 Mercury engine. I have spent several hours testing the stator, trigger, rectifier, ignition coils etc. to no avail. I have no spark whatsoever. When cranking the engine the stator gives up to 110 vac, however the trigger gives no ac voltage. The stator does not give the same voltage ouput on all wires is this normal? According to the tests in the engine manual both stator and trigger should be OK. According to the manual the rectifier seems to be defective. Could this affect the voltage coming out of the stator or trigger? Do you know what voltage should come out of the trigger assembly when engine is cranking? I have tried technical service at Mercury and all that they have given me so far is what is in the engine manual. My local dealer can't understand the problem either. From what I have seen in the answers you have given others you seem to understand these sytems better than anybody else I have tried to contact. Your help would be greatly appreciated.

Thanks,

Phil "

It turned out to be a bad sta

It turned out to be a bad stator which was one of the problems Tony had suspected. If I had more time to do it myself I would have. The bill put a real hurting on the wallet. Hope for a much cheaper season next Spring. Thanks for the feedback- this is a great site thanks to input from Tony and Joe Reeves.

" I have the same problem with

" I have the same problem with my 94 Merc 150. it stalls untill it warms up at 2000 or higher rpm. Timing and spark are ok, fuel pump is ok/runs great at high rpm. I changed 2 prime bulbs and still dosnt seem to hold prime. I will remove anti-siphon valve before removing carbs. "