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Old     (grant_west)      Join Date: Jun 2005       11-04-2018, 5:35 PM Reply   
So I messed up. I didnít change the impeller and it it blew up. I would say 90% of it was in the the impeller pump. I put a new impeller in and cleaned out all I could find. I installed a new impeller and all is good. But when I go wide open. The boat overheats. So Iím sure I have a piece of old impeller stick some where. What should I do.

Itís a PCM GT-40 in a 2002 Nautique direct drive

Here is a pic of my blown up impeller
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Old     (Stazi)      Join Date: Sep 2011       11-05-2018, 7:19 AM Reply   
Probably some fins caught downstream in the beginning of the oil heat exchanger. Take the hose off it that comes from the pump and stick your fingers in there and see if you can fish out any pieces.
Old     (grant_west)      Join Date: Jun 2005       11-05-2018, 9:23 AM Reply   
Well, I ďphoned a friendĒ he gave me some good advice that worked out awesome. I took the thermostat housing off. And found both outlets had impeller pieces. You can see them stuck in this small hole on the right.
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Old     (grant_west)      Join Date: Jun 2005       11-05-2018, 9:27 AM Reply   
This is what the housing had inside it.

Fingers crossed this is all that was left in the system and I should be good to go. Lesson learned. A old impeller can grenade throwing pieces of impeller threw out your motor and causing major drama.
I canít imagine having something like this happen while on vacation and then spending the entire time chasing down overheating issues. Iím just glad it happend at home base and not in the middle of summer or while on Vacation at a remote lake.
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Old     (granddaddy53)      Join Date: Dec 2013       11-05-2018, 10:54 AM Reply   
How many hours and seasons on last impeller change?

No criticism just judging myself as Iím now a 200++ a season now and Iím sure Iíll need to make it annual

Last edited by granddaddy53; 11-05-2018 at 10:57 AM.
Old     (fly135)      Join Date: Jun 2004       11-05-2018, 11:01 AM Reply   
Same thing happened to me. Had to take off the thermostat housing.
Old     (tre)      Join Date: Jul 2002 Location: WI       11-05-2018, 11:34 AM Reply   
Ouch. Sounds like you are on top of it now Grant. I'm also curious how long you went between impeller changes so I know how often to change mine. Currently, I change mine every other year. Here in the midwest, that means every 75-100 hours.
Old     (simplej)      Join Date: Sep 2011       11-05-2018, 1:08 PM Reply   
Our water pump grenaded (not impeller, the pump) and it clogged the exhaust manifold and we needed a new one...good luck.

Start with a back flush
Old     (dgarland0)      Join Date: Apr 2003       11-05-2018, 2:16 PM Reply   
I change my impeller every 12-14 months, regardless of how many hours I put on it. Been lucky have not sucked any pieces into the block, but have blown several impellers by waiting much past 14 months. Cheap part and repair that can do major damage. Not worth it.
Old     (denverd1)      Join Date: May 2004 Location: Tyler       11-05-2018, 9:46 PM Reply   
yep, i got tired of tossing perfectly good impellers in the trash when changing every season. every other season for me.d
Old     (bass10after)      Join Date: Feb 2010       11-05-2018, 11:04 PM Reply   
take a look at the blue sea impellers. They are rated to run dry for 10 min, but i wouldn't vouch for that. Anything thats run dry needs replacing imo its just not worth risking. I change mine out every other year and keep a spare in glove box just in case. I tried to go three years on the last one and ended up changing it on the lake. Only used the boat once last summer so figured it would be ok, but was not the case. No fins were missing which was weird, so either the rubber shrunk and wasn't creating the suction or being the first trip of the year it didn't prime correctly? Not sure. After feeling the difference i would never go back to a standard impeller, although i've seen a standard one last 5 summers before grenade hit it on another boat

Last edited by bass10after; 11-05-2018 at 11:10 PM.
Old     (srock)      Join Date: Mar 2002       11-06-2018, 8:47 AM Reply   
Searching for that odd piece of shrapnel and continued overheating will change your mind on how long is too long to run an lets talk about the need for boat-trailer straps.

The positives; no heat exchanger and easy to access direct drive. If you have 90's into your exhaust riser check them as well. Good luck with the hunt.
Old     (denverd1)      Join Date: May 2004 Location: Tyler       11-06-2018, 11:18 AM Reply   
Originally Posted by srock View Post
Searching for that odd piece of shrapnel and continued overheating will change your mind on how long is too long to run an impeller....
great point
Old     (jonblarc7)      Join Date: Jul 2006       11-06-2018, 11:22 AM Reply   
Went 4 years once because I thought I was smart and store the boat over the winter with RV antifreeze so the rubber would stay soft and not break apart.

I got pulled back to the dock that spring. The impeller separated from the metal center and wouldn't spin, I took me awhile to figure out the problem because when I took the water pump cover off it looked like all blades where there.

Now I change it every other year.
Old     (grant_west)      Join Date: Jun 2005       11-08-2018, 10:01 AM Reply   
Ok to further make fun of myself. So I have changed the impeller in the past. Never had to fully remove the impeller housing. Just simply in bolted the pump and taken out the impeller. When because my impeller blew up sending frag everywhere the impeller housing needed to come out and be cleard of all the pieces. So I took it out cleard all the pieces put a new impeller in and when I did I put the housing in upside down. Thatís right the impeller was in correctly and rotating the right way but I had put the housing in 180 upside down. Itís easy to do because the pump looks like it can be installed either way. But what will happen is that the pump is designed to pull water and becaUse I had it 180 upside down it would now draw a vac and that resulted in no suction for at least 10 mins when I found out, I had no water coming threw. ( simply touch the back of the impeller housing) it should be cool. Like cold cool. Lake water rushing threw the impeller pump will result in the housing cold. Even right next to a hot motor. If your impeller housing is hot on the back side at all your impeller is junk. (Use caution when trying to touch the back of the impeller pump) you can loose a finger or worse. My direct drive has plenty of space and access is no big deal but people please use external caution when and if doing this.
So long story short. I smoked a 2nd impeller. No it didnít blow up but it layed over to where it was not doing itís job well. This time I just threw in a new impeller and all is well. Ran nice and cool for 3 days now
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Old     (srock)      Join Date: Mar 2002       11-09-2018, 7:27 AM Reply   
Keep this in the back of your mind. When the water temps begin to rise with the higher summer water temps you may still have a small obstruction that creates some odd temps.

I had a twin diesel with tranny cooler, supercharger pre-cool and heat exchanger. Those items were all raw water cooled so my damaged impeller was like one of those ispy puzzles and when the Florida water temps rose so did the engine temp gauge. What a nightmare.

We have all seen the why fix it if it ain't broke impeller guys. Most people don't admit to these oversteps so your forthright honestly may save a "life".

Last edited by srock; 11-09-2018 at 7:30 AM.
Old     (granddaddy53)      Join Date: Dec 2013       11-10-2018, 5:39 AM Reply   
My goodness Grant, thatís some beautiful , what a nice put back to the dock every time out!
Old     (ottog1979)      Join Date: Apr 2007       11-11-2018, 8:36 AM Reply   
I'm still having a hard time believing GRANT wasn't a super-regular impeller changer!
Old     (grant_west)      Join Date: Jun 2005       11-11-2018, 9:57 AM Reply   
Has anyone used or uses the Silicone impellers?
Old     (grant_west)      Join Date: Jun 2005       11-12-2018, 9:12 AM Reply   
My friend bought the Globe, Silicone impeller for is SAN 210 it has the GT-40, he said he could not get it to pump? He said he thought the veins of the impeller may be to soft or playable to create suction & or prime the pump. This made sense to me because IMO the impeller only needs to be slightly smaller or the veins layed over then required to Not work. I didnt know if my buddy had bad luck or did something wrong or had the wrong size impeller?
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Old     (TomH)      Join Date: Jan 2014       11-12-2018, 1:44 PM Reply   
I've heard of problems with Globe impellers before, so your buddy isn't an isolated case. Aside from a bad batch of impellers years ago that had a tendency to spin on the hub, you won't do better than a PCM/Sherwood branded impeller for those old Johnson pumps. For the $30ish dollars, I'm in the camp of a new one every spring. That way I don't need to screw around with pulling the impeller during winterization and bagging it, and it gives me peace of mind that it's highly unlikely that I'll grenade one and have to chase pieces.
Old     (denverd1)      Join Date: May 2004 Location: Tyler       11-14-2018, 7:32 AM Reply   
good way to keep the impeller housing going on the right way on a DD, paint an arrow marking the direction of water flow with a paint pen. easy to get those Johnson pumps on upside down.

since we're confessing our sins, I put a pump housing on upside down after a top end upgrade. had the raw water intake in a cooler full of water and a buddy noticed bubbles where it should have had suction. I ended up pulling the heads off and putting new gaskets on a few weeks later after another overheat

Last edited by denverd1; 11-14-2018 at 7:35 AM.
Old     (dvsone79)      Join Date: Dec 2012       11-14-2018, 9:28 AM Reply   
I’m a new impeller every spring guy. $30 and 5 minutes is worth the peace of mind. I toss the old one in the dry box as a spare.
Old     (grant_west)      Join Date: Jun 2005       11-14-2018, 11:19 AM Reply   
Denverd1: Thatís exactly what I did.
Ok no judgment zone. But I canít stand keeping old parts 1/2 used up as spares! I have addiction to throw out everything thatís used.No chance of putting a part thatís used up back in by mistake IMO you want or need a spare then just order a extra one. Iím starting a 2nd tune up kit with 2 of everything I need for all of our boats, that way I have enough for the next time up and a spare
Old     (bass10after)      Join Date: Feb 2010       11-14-2018, 3:12 PM Reply   
My bad I wrote blue sea impellers- I meant to refer to globe impellers, blue sea makes a strainer I believe- I use nothing but globe anymore. Some say they run a few degrees warmer as well, I didnít notice anything other than they have been great and are easy to install as they are pretty slick out of the package.
Old     (srock)      Join Date: Mar 2002       11-15-2018, 8:19 AM Reply   
Originally Posted by dvsone79 View Post
Iím a new impeller every spring guy. $30 and 5 minutes is worth the peace of mind. I toss the old one in the dry box as a spare.
Similar but I toss the old one. I purchase a new impeller and rotate my spare (which is new) into the boat.
Old     (grant_west)      Join Date: Jun 2005       11-16-2018, 3:38 PM Reply   
So this is the advise I would give my self.

Of corse change the impeller on a regular basis. But if you missed it and you happend to have a exploding impeller.

Have a spair impeller and a Spare Thermostat & gasket

Remove the Impeller pump & clear it out.
Reinstall it and make sure itís right side up and Pumping water.
Remove the Thermostat and clear it out (for sure it will have pieces trapped)

Fingers crossed that will be all you have to do.


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