No pee stream from Merc 100 1988. Help!!

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elan86

Cadet
Joined
Jan 27, 2009
Messages
29
Hi guys, no pee stream from my inline 4 100. Have replaced everything I can think of since acquiring this engine last spring. Water pump, impeller, rebuilt carbs, rebuilt fuel pump, had VRO inspected by best Merc dealer I could find. Oh, compression test and new plugs. Very good, even compression. Had boat out several weeks ago with good pee stream. Ran motor in yard two weeks ago with no stream all the sudden. Replaced stat and poppet, still no stream. Removed stat and poppet and cover, water pours out. The stat cover on this motor is upper left side on aft end. The tell tale elbow is just around the corner on port side top of motor. Very close together. Tried compressed air and weed eater line with no luck. Any ideas? dont want to pull the cover off the side of motor if I dont have to. Should I put it in the water then try? Was told backpressure was needed and to push 80 lb leader line up into the holes. Thanks for help.
 
1

1nebel0

Chief Petty Officer
Joined
Nov 28, 2005
Messages
512
Re: No pee stream from Merc 100 1988. Help!!

Ok first of all you don't have a VRO pump..they on on Johnson's....what you have tried normally does the trick... the hose that is used for the stream has to be plugged somehow...if you have a water pressure gauge it would tell you the pressure you have..you need to know how hot the motor is getting and a great tool for that is an infrared gun for aroumnd 50 bucks that you can point at the head to see the actual temp...Merc's take some time when first started to start peeing and the stream is always week unless the unit uses the bigger pump like my 90h.p uses. My Bridgeports and 200h.p. fishing motors have 1-2lbs at idle with weak streams and around 10-12lbs at full throttle..Johnson's put out much more water as most use a much bigger impeller than the merc's...This water issue is such a problem for so many Merc's. Also need to make sure your impeller is still in tack as pieces can break off and end of clogging your water passages...Please let us know what you do to end of fixing the problem as you have listed the typical fixes...Good Luck
 
Faztbullet

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,899
Re: No pee stream from Merc 100 1988. Help!!

If you have water flow at the t-stat the impeller is working. That engine gets the "P" indicator from cold water side of exhaust. Remove the "P" elbow and see if water is comming from block ,if so the hose or elbow is clogged. If not, you have debris in exhaust plate blocking water to elbow,try some compressed air in to the block at elbow and restart to flush,if water exits run a few minutes to ensure it doesnt reclog. If still no water the plate will have to be pulled and cleaned. A lot of people get confused with this motor as t-stat has nothing to do with "P" steam as it exits before t-stat & poppet.....
 
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elan86

Cadet
Joined
Jan 27, 2009
Messages
29
Re: No pee stream from Merc 100 1988. Help!!

Thanks Faz, I agree with your explanation. I removed elbow and have run compressed air up in it with it running and not running. No stream. Am ordering my new gaskets before I take the side plate off. I'm assuming the gaskets are not reusable. Thanks. Will take pics and let everybody know what caused this. I hate when the thread trails off with no answers!!
 
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basn4life

Recruit
Joined
Jul 14, 2009
Messages
3
Re: No pee stream from Merc 100 1988. Help!!

The water pressure on that motor is 1-5 psi at 5,000 rpm's, so you may not see much at idle, especially if not submerged in water and using "earmuffs". I usually will not get a water stream on mine (1989 100HP MERC) if not on the lake, and even then I usually have to be off idle to see a nice stream. Once it's warm, and on the lake, I will see a water stream out the back of the motor at idle. (new water pump housing and impeller here too). You may have a normal condition, unless you are overheating.
 
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