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Monsoon overheating....need ideas


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First off, I'd like to send a huge Thank You to the entire crew. This website has helped me in more ways than imaginable.

However, I have a problem that I can't seem to find an exact answer for. This weekend, I took the boat out for a ride in order to make sure everything was running right. After the motor warmed up by cruising around at 25-30 mph, I decided to see what my WOT RPM and top speed are coming in at with the prop I have. I drove the boat to WOT and then back down to idle. I turned the boat off, and worked on a few things. After 10 - 15 minutes, I was done with what I needed to do, so I headed back towards the launch. On the ride back, I was cruising around 25-30 mph again, and I decided to bring the boat to WOT one more time to check the initial numbers. However, when I reached WOT, the engine took over and brought the speed down to idle, so I pulled the lever back to figure out what happened. I figured that I may have broken the throttle cable. I shut the engine down, and checked the throttle cable. Everything seemed fine. Started the boat again and noticed that the temp gauge was maxed out around 270+. The engine would not let me increase speed past 12-15 mph, so I just idled a couple hundred yards to the boat launch. When I got back home, I immediately checked the impeller. It looks fine, but it is 2 seasons old. It could be my problem, but I've had overheating issues for quite some time. I plan to put in a new impeller, but I feel like there's something more to this issue. The impeller before this one had no teeth left on it when I changed it (I had just purchased the boat). Could some of the intakes be clogged with rubber from the impeller or trash from the raw water intake? What else should I look for? Is there a way to flush the cooling system? I need my engine to stay cooler because when we ride, I always have to stop for a while to let the motor cool with the engine compartment open. Any information or pictures would be greatly appreciated.

1999 Sunsetter LX with Monsoon 325hp

Edited by tp1188
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You will probably find the pieces of your impeller at the transmission cooler (located on the back of the engine (transmission side)). There should be a good picture of it in your manual. Take the cooling water hose off the cooler and there should be a screen at the cooler where you will find the impeller pieces.

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Check the cooler lines from the lake inlet all the way into and out of the eng. I have had the inlet side of the pump clogged before with pieces of impeller. Also replace the thermostat, I have seen them stick open or closed and that could be part of the problem as well.

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You will probably find the pieces of your impeller at the transmission cooler (located on the back of the engine (transmission side)). There should be a good picture of it in your manual. Take the cooling water hose off the cooler and there should be a screen at the cooler where you will find the impeller pieces.

Yep, agree with this post. Check for seaweed or other debris in the hose itself. Couple years back I had a heck of a time with over heating. Result was a clump of seaweed lodged inside of the hose restricking water flow through the transmission cooler.

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I too bet there are impeller pieces in the line. Exact same thing happened to me. Cleaned them out -- and instantly fixed the problem.

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I'll check every water hose that I can the next time I'm working on the boat. I'll also check the tranny screen. I knew the Crew would have the answer. Thanks again!

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  • 3 months later...

I have the same problem... egine overheating on my LCR 340... 06 vride with 240hrs. jus changed the impellar this am and thermostat... also cleaned a couple twigs of sea wead out of tranny cooler screen... fired the boat up on fake lake and ran fine for 10mins... killed it... waxed her then went to repeat the running on fake lake... after about 45 seconds no water came from exhaust and temp started rising above 160 so I shut off engine.... waiting for about 20mins researching, then tried again and everything worked fine... this has happen to me twice... any ideas or help would be greatly appreciated...(it all started last week out on lake when temperature shot up to 210.. so I shut boat down and got towed to ramp. figured it was jus dirty river water or from being on sandbar...well took boat home and wanted to fake lake it but would run hot and no water coming out exhaust... wait till cool then try again and would work properly.)thank crew.

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Water came out the exhaust (for sure) during first try when you ran it for 10 minutes? The other question is, are you sure water is being sucked in? I'm not sure how water could go in without coming out "somewhere".

My first idea is the impeller vanes are pointed in the wrong direction. Next is a clog. To take the thermostat out of the equation, take it out at least till you get this resolved.

If it still overheats after checking these items you have a clog or hoses hooked up incorrectly? Or really hot water at your lake :biggrin:

Let us know what happens,

Steve B.

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Water came out the exhaust (for sure) during first try when you ran it for 10 minutes? The other question is, are you sure water is being sucked in? I'm not sure how water could go in without coming out "somewhere".

My first idea is the impeller vanes are pointed in the wrong direction. Next is a clog. To take the thermostat out of the equation, take it out at least till you get this resolved.

If it still overheats after checking these items you have a clog or hoses hooked up incorrectly? Or really hot water at your lake :biggrin:

Let us know what happens,

Steve B.

Steve this is something new, i ran the boat all last summer, spring and some this summer and this is the first time its happened. im no boat expert but i totally agree to the maybe something clogged i but not sure exactly what... took off like 4-5 hoses and made sure was clear, only 1 (leading to tranny cooler) had couple twigs of seaweed in it, cleared it out.... ive saw post about impeller being installed wrong way, but ive also read that the impellers will rotate the right way reggardless.... but im sure i put it in the way i took the previous 1 out which wasnt damaged at all. so tomorrow i will take your advice with the thermostat and respond. ive heard of ppl getting bad thermostats all the time.. thanks for the info.

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Steve this is something new, i ran the boat all last summer, spring and some this summer and this is the first time its happened. im no boat expert but i totally agree to the maybe something clogged i but not sure exactly what... took off like 4-5 hoses and made sure was clear, only 1 (leading to tranny cooler) had couple twigs of seaweed in it, cleared it out.... ive saw post about impeller being installed wrong way, but ive also read that the impellers will rotate the right way reggardless.... but im sure i put it in the way i took the previous 1 out which wasnt damaged at all. so tomorrow i will take your advice with the thermostat and respond. ive heard of ppl getting bad thermostats all the time.. thanks for the info.

It's starting to point toward a bad thermostat, but water will still make it out exhaust, even when thermostat is closed...hmmm.

And you are sure it really is hot? Just throwing out there maybe a gauge issue, but I'm guessing you can tell it's good and hot.

Steve B.

edit: You know what, I'm wondering if your circulating water pump has gone bad !

When you get a chance, when engine is cold, key out of ignition, take your hands and try to rock the circulating pump by grabbing the pulley. If it rocks a lot, it may be shot.

Edited by Steve B.
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Steve...?? is the circulating pump ...the pump that the impeller sits inside...cuz I did notice a little trembling inside the instrument that the impeller sits in.(nothing major but noticable.) Thanks for the info.

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The circ. pump is not the impeller housing(raw water) pump. Circ. pump (and pully) is just above the crank pully. It has a weep hole at the bottom that should weep if it's bad (or the pully will wobble if it's bad). Auto engines only have one pump, the circulating pump.

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Steve...?? is the circulating pump ...the pump that the impeller sits inside...cuz I did notice a little trembling inside the instrument that the impeller sits in.(nothing major but noticable.) Thanks for the info.

no...circ pump is above that. The impeller housing will move a little from engine speed but iof excessive I'd remove then re-attach mounting like your putting on tire (keep going across). Too much play could contribute ot premature seal and bearing wear which will leak water out teh rear which will affect water flow. You should have NO leaking from the backside of the impeller housing.

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I have no leaking whst so ever.. will change the thermostat again and hopefully it was just a faulty 1... ill post afterwards. Thanks

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do you have an inline freshwater flush or are you using a true plunger style fake a lake?

Might be unrelated, but I have an ongoing temp problem as well. Starts at 160 then slowly builds to about 180 then slowly goes back down to 160.....all day long. After reipping everything apart and not finding a thing, I and "deducted" that the issue is electrical not mechanical. I have an 07 Sunscape and beleive that the fly by wire voltage component is most likely my issue. Just sharing in case your issues is similar.

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Jason and 85 are correct about the circulating pump above the raw water pickup.

The raw water sucks up dirctly from lake. Water then flows various places, mostly via the thermostat and it's housing. I believe from there it feeds the circulating pump, which sends it into the engine and after a few mixes, is sent out the exhaust.

It may be possible, your raw pump and system is fine, but circulating pump not functioning properly.

I'd first try no thermostat. If ciruclating pump is bad, it will still overheat. If pulling thermostat fixes it, then it was the thermostat,

Let us know how it goes,

Steve B.

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Ended up being bad thermostat... picked up a temporary 160' thermostat until the marine 160' thermostat comes in from Bakes... thanks for the help BuCrew

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