mercury water flow question

[CRAZYHORSE]

Had my boat out wed night. its a merc 150 black max, probably late 80's. it was running a little rough so we changed out the plugs today. at the same time we changed out the impeller. hooked the water to it and fired it up. all seemed ok, but there was only a small stream of water shooting out of the back of the motor (from the head). it was kinda come and go. water seemed to be circulating ok. ran it on the muffs for probably 30-45 seconds twice. is there anything else i shold be looking for? just don't want to ruin a good motor. thanks in advance for the advice??

crazyhorse

 

[fisherpal2k]

Make sure the water is on all the way. Cause if not the pump will starve. Also some of the motors have thermostats in them and they have to warm up before opening all the way. </p>

If you rev it up (out of gear of course) the water flow will pick up. Most of the Mercs will pull more water when under a load. I would just rev it up to a couple a thousand and drop it back off. Don't leave it at high rpms without a load on it. </p>

 

[Flippen*1]

CH, I have an 84, same model, here is how it was explained to me. The motor has not one, but two thermostats, one on each side of the head. Until motor heats up, they recirculate the water instead of sending it out the back. My motor will run about 5 minutes with the muffs on it before it starts getting a good stream out the back. Why they were made this way, I have no idea. I do know that when taken care of, these old Mercs will last a really long time. If after a while you still are not getting good flow out the back, I'd take it to Paul Nichols in Soddy. Good luck.

 

[CRAZYHORSE]

Took the boat and put in in the water at wolftever this pm. ran it for about 5 minutes. talked with a man who seemed to know his stuff. he said it was putting good spray out the exhaust which was good. there was still nothing coming out the little hole at the back. he said it may be clogged, and it was. it was holding 6lbs of water pressure at idle, which he said was good. he also said some of these old mercs dont push out a hard stream of water anyhow.

i guess ill run it this saturday and we'll find out for sure!!!

crazyhorse

 

[ChooChooSnakeMan]

Crazyhorse,

I don't know for sure about 80's vintage Mercs but I do know that the later model Merc engines use a high volumn low pressure water pump. It moves a lot of water but not at high pressure so the flow from the tell tell hole is not shooting out like on some of the Johnson Evinrude products. The comments about the t'stats are right on as well. With the cool water temps this time of the year it can take several minutes for the t'stats to open. The best way to know if your water pump is working right is with a water pressure gage. Since you are showing 6 lbs. at idle, I would think you are good to go. Good luck with your fishing and be careful with the lake down!

 

[CRAZYHORSE]

thanks for all the good repies. i believe we are good. sometime it feels better to get others feedback.

i appreciate the help.

c-horse

 

[jjoey312]

As long as your warning horn is working the way it should it would warn you before your engine would be damaged. On a merc the amount water flow out the indicator hose could be caused by several things. If the sensors in both heads are good along with the warning horn your in good shape. Like one of the earlier post said 6 pds at idle is good. Running it should show at least 14-15 psi it could even show upwards of 30 psi on some motors. This is all to do with where and how the water pressure tap line is connected.

ps IF your merc is a late 80's engine it would be a good idea to disconnect the auto oiler if it is not already disconnected. I rebuild at least four to five of these engines a year due to oil pump failure. Call me if you have any questions (706)891 9921 ask for Joey.

 

[Liveliner]

I have a 2002 150 Merc and it has a new impeller. When My engine is cold, it will not pee. As it warms up it starts to spit.. Even when hot it does not pee a hard stream at idle. I do not know but have you tried water pressure from your garden hose to push any blockage from the pee hole?

 

[Liveliner]

[No message]

 

[CRAZYHORSE]

That guy told me to clean the hole out because somrtimes they get trash. I did this and saturday and it was pushing water out there good. I noticed that the more i trim up the more water pressure i had. anyhow ran it about 30 miles total on saturday and it ran like a champ.

crazyhorse