Understanding the MR 1 cooling system

A look at the engine cooling on Yamaha's MR-1 engine

[@TheOriginal_T-Bilt]

You did an outstanding job with this video! As many have said, Thank You.

[@thefpvlife7785]

It's never too late to thank you for such a great informative video. The time you took to make this video is grateful.

[@kennyschopperz]

I am gonna ditto @ The FPV Life 's comment. This is an excellent "mechanics view" of this system. I have been doing PWC's for a little over 6 years now. I am a diesel mechanic by trade, but I have been working on all things since I was about 10. I am 39 now, and I can tell you that this is the most comprehensive video to date that I have seen on this engine platform. I have a "03 FX cruiser, it had gotten water into the crankcase, via the water outlet pipe O-ring on the front of the cylinder head, and forced it's way under the valve cover gasket, due the grommet on the outer portion of the valve cover being quite the seal of integrity LOL. I fixed it after getting on HELL of a deal on it for $600. My family has enjoyed it for 4 years now, and I have always noticed there isn't a very good deal of water coming out of the exhaust flow indicator. I get a little under throttle, but last summer I notice it smelled like exhaust and had some vapor flow coming out of it. So I am thinking that the bellows joint is cracked. It's always been a freshwater machine, but the outlet pipe I had fixed years ago had quite a bit of corrosion in that bore when I repaired the o-ring. So the thought of the block and water passages being blocked concerns me. It has never overheated, and we pull kids on tubes like gang busters every summer. So that makes me feel a little more confident about this just being more of the exhaust joint issue. Because if it has exhaust gas pushing the water away in the joint, the water it just exiting out of the rear, instead of the indicator.

[@HPGrimmace]

I recently bought a 2003 SR230. First time out today and my starboard engine is overheating. It runs perfectly while on the hard and with a hose attached. In any case, MUCH thanks for such a thorough overview. This video will serve as a great guide for troubleshooting.

[@onelove9101]

We are having the same problem.

[@biorcgis6383]

Great Video...one note of importance is that the arrow at 4:07 out the front of the oil cooler into the top of valve cover on the engine rear is not a cooling line, that is an oil line. It drops into the valve cover to an open hole over the cam shafts and the internal hole is blocked off with a plate attached with an allen head. At least that's what I see in the engines that I have apart right now.

[@shanelowe3902]

As others have said, thank you for making this video! It is extremely helpful to me while troubleshooting a pesky blockage that's causing an overheat issue.

[@HKPSG1Shooter]

An important note regarding the cooling system: if you ever have water in your oil, the FIRST thing you want to check is the exhaust manifold as those mating surfaces can corrode, and being that close to the cylinder head, with the valve overlap and aggressive cam lift of the MR-1 engine, it will ingest water from this point. I had this issue with my engine... but suspecting it was a head gasket, I removed the cylinder head before I removed the exhaust manifolds. On the other hand, if exhaust manifolds and gaskets look OK and the engine has good compression, then the next thing to check is the oil cooler/tank. Cap off the outlet hose with a fitting and a pressure gage, hook a garden hose to the inlet on the bottom of the tank, and using a valve, slowly bring water pressure up to around 15 PSI, then let it sit for 15-20 minutes. If there is no loss in pressure then the head gasket would be the next suspect. I say all of this to save anyone the difficulties involved in disassembling the entire top end to get to the head gasket, as the intakes/throttle bodies, valve cover, camshafts and caps must be removed before you can access the cylinder head bolts.

[@stevez9764]

great video ! Thanks , it really helped to fix my overheating FX140 wave runner .

[@nyinfamous2k2]

Much appreciated , This video helps me a lot to understand my older yamaha with the MR1 . great work

[@henrygarcia4438]

Great! Appreciate the video. Saved me lots of time on a related issue.

[@jackward9435]

Thank you so much for this video! No other source for this information - You are a life saver!!!

[@HKPSG1Shooter]

Found the problem! The short section of hose between the Y fitting and the distribution port (1:25) has a pre-formed bend. This section of hose was collapsing at lower PSI, causing it to overheat at idle, but at higher speed, it was able to feed enough water to the engine. Replaced it with a longer section of hose, with a nice, smooth radius, instead of a sharp bend. Works fine now.

[@antharding]

Thank you so much for taking the time to make this video and explain it so well. It will be useful to a lot of people, and considering you are explaining marine craft engines, who knows, you may be helping to prevent people getting stranded out at sea :) Can i suggest you add the words, Yamaha, VX110, FX140 and FX160 to your title as this engine is in many of these waverunner models so i expect it will massively boost the amount of views this video gets, and help even more people.

[@jpdoherty9143]

Fantastic video, thank you so much

[@briancorkery4083]

Awesome. Coming from stern drives, I didn’t realize that there is no tradition water pump impeller that needs regular replacing

[@ProcessRacing29]

Hello Great video, Thank you for taking the time to show good pictures of all the routing,. At 4:09 you show the oil tank vent hose ( i believe its an over flow/slosh drain over the timing chain) there is no water here this connects directly to the OIL tank. Do not put any water or flush water here!!!!!

[@stephenjohnston6623]

Excellent information! Thanks for taking the time to share. I have learned some great (hard to find) information from you. Well done !

[@antsbradley]

Great video, thanks for taking the time to make it

[@NZBitcoiners]

This is gold my friend, working on my WaveRunner fx110

[@elementtuning]

Very helpful. Thanks!

[@turboshelby8322]

Mr-1 engine is one of best engines.

[@Donkor640]

This video is very well done. Feel free to make one for all the operating systems. LOL! 🤩🤙

[@dano5173]

Excellent video!

[@howardisaacson6329]

Super informative! Thanks!

[@andrewkarstens3924]

nice job on the video helped a lot

[@andredesouza9767]

I appreciate very much this video, thank you !!!!!

[@WardogsMr]

excellent video

[@mteibel]

Great video buckbuck

[@pastorfred3460]

Thank you!

[@gcam474]

Fantastic! THANK YOU!

[@kkutube1972]

Thank you.

[@tomokin666]

Great video. Yamaha should make one like this. Are you planning on making a Yamaha TR1 engine version of this video? That would be very helpful.

[@bobbyhoran3387]

Great Video, do you know if one of these hoses came loose if it would flood the engine compartment? I have 2005 AR230 HO, that the engine compartment flooded on. Thanks

[@user-ei6zy3pv6h]

If they put arrows on the hoses to inform you which direction the water flows you might understand or color code them but that would make them more expensive and not necessary to a mechanic. Find a good mechanic and tip them for doing a great job. They will go the extra mile for you, stay late, rob a part from another job to float your boat, beg the parts guy to get what you need. Make a relationship with a good mechanic or technician yummy food , cold drinks on a hot day and a crisp twenty, The bill you pay at a repair shop is up to the manager not the mechanic, the work that is performed is. if you care about them by showing some gratitude and not complaining like the last guy trying to get it fixed for free they will take care of you so welcome to the VIP section my friends.

[@jetz40]

Thank you!!

[@brimacs]

brilliant cheers

[@CaptainLeonsBoatingandMore]

Hey great video, well done. I know it was made quite some time ago, but still relevant to many. Knowing the cooling system as you do, what are your thoughts why some dealers pump in some non-tax antifreeze before long cold storage, some say with the engine being self-draining, there is no need, thoughts?

[@joefishtale]

you are a saint

[@SconHeadVideos]

Should water be coming out the nozzle on the side of the ski when the hose is attatched and running at idle? Nothing coming out of mine, checked the pipe which exist the ski, that is unblocked so no idea why nothing is coming out

[@cootingram6265]

On the hose i have water exiting through the jet pump and exhaust but none is coming from the fitting on the stern above the jet pump. I believe its from the engine block that passes the thermostat. After 10 mins on the hose it overheated and got to 250 f. What do you think the culprit could be? Any help would be great, thanks

[@srm9261]

4:10 is incorrect, (from top of the cooler into the engine) That's an oil line NOT a water line

[@wutisay]

Very informative. Complicated system this is.

[@cootingram6265]

I have an 06 sx230 that I can't figure out. Within 5 mins on the lake it over heats and engine drops rpms. I've changed the thermosensor and pulled the engine and checked for salt water corrosion and it was minimal. Ive used non contact thermometer and I don't see the engine over heating, both engines are the same. Good pee flow and no cavitation. I'm stumped. Would the thermo sensor be bad? Do those put the engine in limp mode or will it just shut down the engine? Any help is much appreciated

[@mikemike827]

Did you find the problem yet?

[@cootingram6265]

@@mikemike827 I took apart the exhaust and cleaned any scale build up. Wasn't bad enough to cause restriction imo. I replaced the thermo sensor and it's still doing it. I'm going to replace the 2 thermo switches and see if that works. It not then I'll probably burn it down!

[@mikemike827]

coot Ingram just one motor? Did you look to see if water hose collapses at idle but full flow at higher rpm?

[@cootingram6265]

@@mikemike827 yes just the starboard engine. I've inspected all the cooling lines and everything appears to be in good shape

[@123partyrentals]

Did you resolve your issue? Im having similar issue like you.. my engine is running at 6krpms.. but if i put it on neutral and push it again .. goes to 10rpms and back to 6krpms. Temperature light is on.. but engine is not oveheating

[@Engnrtech09]

Mine ( YAMAHA FX140 2002 ) has an Overheating Warning Light coming up after couples of minutes of running in the seawater. Suddenly, I’d started the pwc to flush after 48 hours and after a few seconds of turned ON the buzz started to warn about OVERHEATING. What it could be ? Thermosensor ?

[@user-ei6zy3pv6h]

I have an 02 that I just went through an inspection. Is there water flowing out of the through hull ports when it’s running and warmed up ? These are there to let you know if water is flowing. Check it out there is one on each side. When they are you can check the temp of the water with your hand 🖐 at a minimum remove and clean your thermostat. It’s actually not too difficult and located at the top beside the oil tank I bet it’s full of poop, calcium clean it up and test it in a cup of hot water to watch it open. Check your anode, easier than you think . Undo the little bolt on the side only not the middle one, it will pop off easy. There will be a rubber o ring. Flush clogged lines if your thermo is plugged up nasty, so the y pipe line that goes back to the intake at the impeller and the through hulls at the sides with water and compressed air. There you go my friends , Bob Ross

[@eltanoadrian]

Podrías traducir al español..gracias

[@uwimanaramadhani8088]

Ilouze axereration

[@neilrobertson1345]

What a way over complicted system OMG

[@InNeedOfSpeed]

Works very well though :) The MR-1 engine is legedarily reliable.

[@marshallamplification60TSL]

I have an overheat issue w 1 engine on my 2007 AR210. No issues with these engines for over 12 years. This is a great video. I agree though w you Neil..seems like too many areas can affect the cooling on these engines. Like Victor said...these are super reliable engines for the most part.

[@user-ei6zy3pv6h]

No issues in twelve years and it’s over complicated? That’s called reliable, so in twelve years did you ever replace the anode in the case or your thermostat? Most owners wait for something to go wrong then fix only that problem. All you really have to do is clean mechanical things and they work. These are open cooling systems which work well and for many years but this is mechanical not digital ok, most guys don’t even flush there engines after a salty ride just hose off the hull and trailer. After you ride and the engine is hot and so is the oil. At a minimum, PULL OFF THE SEATS AND REAR TUB TO LET OUT THE MOISTURE FROM YOUR HULL please this will be the laziest easiest thing you can do. If you don’t have any info on how to maintain and that means service something mechanical it will fail. How many years of reliability do you think you might get with a closed cooling system and a supercharger ?

[@user-ei6zy3pv6h]

Neil, and to all of you other Neil’s, there is only one thing really , are you ready for it ? Here it comes ,,,,,,,,water flow

[@comfortwantsyoudead7067]

I have a further question can you answer ?

[@antonsergeevich3177]

Excellent video!