Boat overheating

[atropine]

I have a 2004 Wakesetter 23 LSV, 170 hours, 340 Monsoon. I installed a Fresh Air Exhaust system and an ACME 1235 prop earlier in the week and took it to the lake on Thursday. Put the boat in the water and idled around for a few minutes while motoring out of the harbor. Boat started overheating (hit about 190) and idled down to safe mode. Lifted the engine compartment pulled the impeller cover off to find it was disintegrated. Took out my spare and installed it, then ran for another 4 hours at wakeboard speeds with no problems. Then coming back I was pulling a slalom skier at about 30 mph and it hit 190 again and idled down again. At idle speed it would cool down to about 160. Came home, pulled the impeller cover again, impeller looked good. Replaced the thermostat with a new one from Napa (160 degrees). Then got smart and searched on this forum and others and realized that I should have checked the oil cooler screen. Pulle it off and found the screen almost completely plugged with shredded parts of the old impeller. Cleaned it out good, then took it out again today. Started up great, ran steady at 3700 rpm holding steady at about 32 mph and around 165-170 degrees. 3800 rpm did fine, about 170 degrees. But if I bump it up to 4000-4100 rpms (38 mph) it would jump up to 185-190 degrees and shut down to safe mode after running about 4-5 minutes sustained at this speed. If I let it cool down and run at or less than 3800 rpms it does fine. I unhooked the water hose at the incoming side of the oil cooler and ran the engine for a few seconds to flush any remaining impeller debris out of the hose; nothing came out except water. So now I am stumped. I don't think any of the modifications was the cause of the impeller exploding; it was time to change it out and I think it was just coincidence. But now with a new impeller, thermostat, and cleaned water lines I don't know why it can't run at sustained high speeds without overheating. I never had a problem running those high rpms sustained before. I know the fresh air exhaust does limit exhaust flow at high rpms and they don't recommend running sustained high rpms with the system, but I thought these motors were supposed to run up to 5200 rpms and I though 4000 was well below this. Maybe the slight increase in backpressure from the fresh air exhaust is leading to higher temps? I called Larry Mann at Fresh Air Exhaust and he said that they have over 500 of these systems on the water and no problems with overheating that he is aware of. I think I will take the FAE system back off and go to the lake on Monday and see if the problem is resolved. Problem is I took off the through-hull flappers to mount the flange tubes for the FAE system. Does anyone know if I can run without the flappers in the exhaust system or will I end up sucking too much water back through and into the engine? I want to just leave the flange tubes attached but remove the rest of the FAE system. This leaves me with essentially just big open through-hull holes for the exhaust system, just like what is there originally but without the flappers. If the overheating problem is solved then I know it was the FAE system. I don't mind if this is the problem, as I don't ever really need to travel at sustained speeds of 4000 rpms and I love the noise reduction from the FAE system.

[Pistol Pete]

Without the flappers, I'd be real careful about running the boat in reverse and water backing up into the exhaust system. As long as your mindful of it, I don't think it'd be a problem. But, it already sounds like you're just going to live the the FAE and no high R running....

"If the overheating problem is solved then I know it was the FAE system. I don't mind if this is the problem, as I don't ever really need to travel at sustained speeds of 4000 rpms and I love the noise reduction from the FAE system."

[Surfin247]

I have a 2004 Wakesetter 23 LSV, 170 hours, 340 Monsoon. I installed a Fresh Air Exhaust system and an ACME 1235 prop earlier in the week and took it to the lake on Thursday. Put the boat in the water and idled around for a few minutes while motoring out of the harbor. Boat started overheating (hit about 190) and idled down to safe mode. Lifted the engine compartment pulled the impeller cover off to find it was disintegrated. Took out my spare and installed it, then ran for another 4 hours at wakeboard speeds with no problems. Then coming back I was pulling a slalom skier at about 30 mph and it hit 190 again and idled down again. At idle speed it would cool down to about 160. Came home, pulled the impeller cover again, impeller looked good. Replaced the thermostat with a new one from Napa (160 degrees). Then got smart and searched on this forum and others and realized that I should have checked the oil cooler screen. Pulle it off and found the screen almost completely plugged with shredded parts of the old impeller. Cleaned it out good, then took it out again today. Started up great, ran steady at 3700 rpm holding steady at about 32 mph and around 165-170 degrees. 3800 rpm did fine, about 170 degrees. But if I bump it up to 4000-4100 rpms (38 mph) it would jump up to 185-190 degrees and shut down to safe mode after running about 4-5 minutes sustained at this speed. If I let it cool down and run at or less than 3800 rpms it does fine. I unhooked the water hose at the incoming side of the oil cooler and ran the engine for a few seconds to flush any remaining impeller debris out of the hose; nothing came out except water. So now I am stumped. I don't think any of the modifications was the cause of the impeller exploding; it was time to change it out and I think it was just coincidence. But now with a new impeller, thermostat, and cleaned water lines I don't know why it can't run at sustained high speeds without overheating. I never had a problem running those high rpms sustained before. I know the fresh air exhaust does limit exhaust flow at high rpms and they don't recommend running sustained high rpms with the system, but I thought these motors were supposed to run up to 5200 rpms and I though 4000 was well below this. Maybe the slight increase in backpressure from the fresh air exhaust is leading to higher temps? I called Larry Mann at Fresh Air Exhaust and he said that they have over 500 of these systems on the water and no problems with overheating that he is aware of. I think I will take the FAE system back off and go to the lake on Monday and see if the problem is resolved. Problem is I took off the through-hull flappers to mount the flange tubes for the FAE system. Does anyone know if I can run without the flappers in the exhaust system or will I end up sucking too much water back through and into the engine? I want to just leave the flange tubes attached but remove the rest of the FAE system. This leaves me with essentially just big open through-hull holes for the exhaust system, just like what is there originally but without the flappers. If the overheating problem is solved then I know it was the FAE system. I don't mind if this is the problem, as I don't ever really need to travel at sustained speeds of 4000 rpms and I love the noise reduction from the FAE system.

If the problem ends up not being the FAE, you could have blockage in your exhaust mainfolds and/or exhaust risers which could lead to an overheating symptom.

[atropine]

I have never taken the exhaust risers/manifolds off; how difficult is this to do? It seems like it should be rather simple. I didn't really think it would be necessary as I figured that the water passages though them were wider than the openings in the screen at the oil cooler and thus there should be nothing big enough to plug them up...

[Surfin247]

I have never taken the exhaust risers/manifolds off; how difficult is this to do? It seems like it should be rather simple. I didn't really think it would be necessary as I figured that the water passages though them were wider than the openings in the screen at the oil cooler and thus there should be nothing big enough to plug them up...

Corrosion. Also, there have been threads about problems with certain exhaust manifolds and risers. Not sure on the years. Use the search to see. You could also have blockage in the actual holes of the tranny cooler. I used a shishkabob sick (wood) to make sure each of those little holes that make up the cooler are not blocked. Only other things I can think of are: Enough engine oil, Ciculating pump leak or more likely because of overheat at only high RPM's is belt slippage. Has the belt been changed recently, is it tight enough. Ciculating pump leak should show with water in the bilge and at high RPM's water spraying around engine compartment. I'm also sure you checked engine oil level. If there are any other ideas I'm sure people on this site will chime in.

[wienrdog]

Could be the auto thermostat you put in... Marine thermostats are usually higher flow rates than auto thermostats. IIRC, there was someone on the old MBO or Wakeside that had a problem with that.

Could also be a slight air leak around the impeller housing. It's able to keep up until you turn more RPMs, then it starts pulling a little bit of air & not cooling as well... Be careful with the impeller housing bolts/screws as they are brass & will snap off pretty easily.

[atropine]

Thanks everyone. I figured it out today. I took off the raw water line where it comes into the impeller housing and found a bunch of pieces of old impeller jammed up inside the intake side of the impeller housing. I wouldn't have thought that pieces could get jameed up on that side, but they did. I also should have thought about it sooner.... Anyway, problem solved and boat runs great and holds at 160 degrees throughout. I never did take off the fresh air exhaust, and I can't tell any difference in the boat's performance with the FAE system other than the massive noise reduction. Thanks again everyone for the help.