18hp evinrude cooling problems

[riverbronzeback]

Got a nice find on craigslist. A 63 evinrude 18hp which is very clean. Guy says he replaced the impeller and still doesnt pump right. I see no evidence of it overheating. It has spark and compression is 100 on both. If he put the impeller in right am i right to assume most likely a plugged impeller tube or the passages in the powerhead. I only paid 50 bucks for it. I just got done rebuilding a 57 johnson 18hp and litteraly have taken apart from start to finesh so i know these pretty well. What else could keep it from not pumping right other than a restriction somewhere. The guy is an engineer so i would think he could get the impeller back in right. What do you guys think. I either got a steal or another parts motor which would be fine. Also another motor stand, good gas tank and spare prop.

 

[dougdad]

I think ya got a deal either way. if he didn't get the drive pin in correct for the pump or forgot it it is an easy fix. I would take it apart, blow out all passages, tubes ect. check the pump for damage and proper assy. and go from there. My friend just had pump problems with his and it turned out a muddubber wasp had built a rather large nest up inside the inlet just far enough to not be seen. :mrgreen:

 

[huntinfool]

The impeller could be in backwards. (trying to push instead of wipe) Or the pee tube could be plugged. It could have scale build up inside...but that is very rare unless it has seen a bunch of salt use.

 

[bassboy1]

The most common mistake is forgetting to put the woodruff key in the impeller when installing. If not, you will need to start pulling it apart to pinpoint the blockage, and then solve it. I can't remember if that year had a thermostat, but if it does, I would check on that right after you check the woodruff key.

If he installed a new impeller backwards, it would have righted itself, so that won't be an issue.

 

[riverbronzeback]

Pulled lower unit. Woodruff key in properly. Impeller looks good. What is the best way to go about blowing out the passages. Should i pull the powerhead if the t-stat is ok. How can you tell if t-stat is bad. Also good news is lower unit seems ok and shifts properly but the guy had the shift linkage adjusted wrong so it wouldnt go in forward. Just had this problem with my 57 18hp so i know it can be tricky. And yeah i know i got my moneys worth anyway. I have another powerhead that i can swap on so either way i got me another motor for 50$. Today was a goood day.

 

[huntinfool]

Airhose. Blow up the pee tube and the waterpump tube. You should have plenty of airflow. If not then there could be a problem inside the powerhead. (scale buildup) I'd also try the water hose up the waterpump tube and see if you can force any water through. If you get plenty of water there, then your back to the water pump.

Usually when a motor wont pee, we run air up the pee hose and that will usually fix the problem right there.
Good luck.

 

[bassboy1]

Exactly. Pull the lower unit, and blow down the water pump, to be sure that there is no blockage down there. Then, blow up the water tube, and feel for a good volume of air out the water port on the midsection (that motor has no pee tube). Then, from the midsection to the water tube. Some water also exhausts down under water, so you will feel some air out there, but you want a good volume out the midsection. Keep in mind, an air compressor can blow 120 or so, but a water pump only pumps at about 8 psi, so you can have air come through, but then the water won't make it. So, make sure you are getting the full volume of air.

Also, some motors (maybe all - don't know when OMC started it) with a thermostat will have a poppet valve. This will open up when the thermostat is shut to shortcut the water back to the midsection port. Thus, when the thermostat is closed, it would still appear as if it is pumping water. That means it is real important to check the function of the thermostat. That is done by removing the T-stat, and taking it up to the kitchen, when your wife is not home, and putting it in a pot of lukewarm water. Then, put a thermometer in the pot, and put it on the stove. See what temperature the thermostat opens, if it opens. I think they are supposed to open around 160 - 170, but it would be wise to check.

 

[riverbronzeback]

Blew out all passages like bassboy said. Put back together pumping water real good. I have a infrared thermometer that i use to check temps on motors. Seems to run around 100 degrees or so except on the top bypass cover where the fuel pump mounts. It got to around 130-140. My 57 johnson stays at 90-100 everywhere i check. Havent checked tstat yet cause i have to remove lower cowling and couple other things to get to all the screws. Does anyone know if the 63 evinrude 18hp has a tstat cause my 57 johnson doesnt. Would be nice to know before i pull that apart and find no tstat. Opinions? Thanks. Oh forgot, has a pretty consistent miss. Maybe has to do with the upper cylinder overheating?