View Full Version : help! over heating engine/on vacation day one

07-04-2008, 09:02 PM
I'm out of town at a buddies house for a week. He has 04 a mobius ls. Went surfing, within 10 minutes (I'm behind boat) it starts smoking(whitish/blue). Temp is 200 plus. Dealership just summerized this week. Issue is the boat cannot be easily trailered and taken to dealership(issue with destroyed boat launch due to high water). Is this most likely a water pump issue? What else could it be?



07-04-2008, 10:10 PM
Check all of the intake area... scoop on bottom, undo the hose where it goes from intake to water pump/impeller...
I would check impeller as well to see if it is intact.
If this is as LS as you say, being a direct drive, you should have no trouble checking all this.

Could EASILY be trash in the water intake...or a bad impeller..

07-04-2008, 11:00 PM
could be a stuck thermostat, you csn pull it out and run without it, specially in hot weather.

james yarosz
07-05-2008, 08:24 AM
The intake water line goes to the trans cooler before it gets to the water pump.The inlet side of the trans cooler has a screen in it.Mine gets weeds in it .I clean mine out a couple times a season.

07-06-2008, 11:30 AM

Thanks for the advise. It was the impeller (spelling?). Easy repair except that most dealerships were closed on the 5th for the holiday. Mastercraft sales guy went into his parts department (closed) and got the part. Lesson learned, carry a spare!


07-07-2008, 11:22 AM
I have an LS. Where is the impellor and how does one change it? I think that would be something I should know how to do.


07-07-2008, 11:59 AM
Garn I too would like to know the answer to that question? I am a new LS owner and not very mech inclined, but would like to know how to change the impeller and where it is located..........

07-07-2008, 09:55 PM
Here is a post from a while back that I made for changing one on an LSV. Yours will be MUCH easier, but you can get the idea. The impeller is on the left side of the picture below behind a plate with four tiny screws. In the LS, you shoud not have to remove the entire pump, just the front plate. Remove the front plate and pull the impeller straight out, replace with a new impeller and gasket and put the little plate back, done.

Quote: JesseC
Well I guess that there are two reasons that it is difficult the first time. The first reason being that it is the first time and everything in a V-Drive is upside down, backwards and really hard to get to because you have not done it before. The second reason is that the outer edge of the pump flange (red arrow in photo below) gets rusted to the harmonic balancer. After you remove the pump, use some emery cloth to lightly polish this area as well as the area in the harmonic balancer. Do NOT sand it, just polish with emery cloth or some really fine sand paper. The entire process can be done from the Port side of the engine compartment.

Here are my steps; they may be different on the newer models

1) Remove engine wall separator from Port side
2) Remove blower to get better access
3) Remove hoses from pump assembly
4) Remove the single bolt from the support arm on the bottom (6mm I think)
5) Remove 3 bolts from Flange to Harmonic Balancer (8mm I think)
6) Rotate pump to free the bottom post from the support arm
7) Grab pump and wiggle from side to side while cussing at the devil for not letting it come loose
8) Pump frees itself smashes your knuckles into the exhaust and your removal is complete.
9) Remove cover plate and clean gasket from pump and plate.
10) Pry out impeller (many methods here, screwdrivers, pullers, Vice Grips, I go the route of Vice grips with thin nose)
11) Inspect pump and internals
12) Lube new impeller and housing (I use plumbers grease)
13) Push impeller into housing while rotating flange
14) Put gasket and cover back on
15) Polish pump flange and harmonic balancer with emery cloth
16) Put the three center bolts back first and tighten in a circular pattern to confirm the flange is flush
17) Put bottom bolt back into the support arm
18) Re-attach hoses
19) Drink a victory beer!!!!

07-08-2008, 12:05 AM
The direct drive models have easy access to the impeller. 3 screws and the cover is off. You can also bump the starter to get it loose. I always carry a spare.

07-13-2008, 11:49 PM
Garn and Bambam26, sorry guys I was without internet access last few days. As others have suggested it is an easy repair on an LS. My friend's boat is a 2004 LS. Remove the clam shell cover completely to gain access. The raw water pump and cover is on the bow side of compartment approximately ankle high. On his we removed the water in hose and water out hose for extra working space and to check for debris. The cover had 4 screws and a gasket between it and the impeller housing. The impeller (johnson 812 I believe) came with a new gasket and lubricant to help with installation. If you have not ever made this type of repair you will think that the new impeller is too wide, however this is not the case. Coat the impeller liberally with the lubricant and twist impeller to start to seat it. As the teeth on shaft line up with the teeth on the metal ring of the impeller it will no longer twist. Just push firmly and it should seat fully on the teeth. We just then placed the new gasket and the 4 screws and all worked great! Total replacement time less than 15 minutes. Used boat everyday this past week.

My buddy did not have his engine manual but we found it online. Hope this helps.


07-13-2008, 11:54 PM
I should have read Jesse's post completely before posting. His discription is right on.


07-15-2008, 10:58 PM
On the newer LS the raw water pump is mounted directly in front of the engine crankshaft pully. And the blue smoke is from the rubber exhaust hose burning. See my post on exhaust and transmission. I would say that most of the time (ok with us all of the time) I have never had an impeller failure, but rather a blockage of the intake system first then impeller failure. I have actually used the same impeller for years (inspect every spring and if it hasn't taken a set and has no damage back in it goes). But if you have a system blockage it will also damage the impeller. We ordered our new LS with the intake water strainer, it is clear and easily removable to clean debris and you can see if the water is being sucked up into the engine. I would have to say it was one of the smartest options we ever ordered and they cannot be too expensive if you would want to put on on any of these boats. Best thing about it is that you can visually see if the water is flowing!