Ski Boat Overheating and Cooling 101

SkiBoatPartsOnline.com Presents Ski Boat Overheating and Cooling 101 a brief look at finding, and correcting the most common overheating cause, and an explanation of basic ski boat cooling parts.
Most parts discussed in this video can be found here:
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Sea Water Strainer:
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Water Intake Grated Fitting:
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Water Pump, Johnson F6B
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Impellers
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[@crgeorge1]

Great video and 100% spot on! Adding a strainer to my FWC Mercruisers now... For impellers - I've changed mine in 100, 300 and 500 hours and they always looked like new (always OEM) - I now chance them every 5 years as they last (unless they run w/o water and that destroys them), but on that Johnson - 100% so easy to chance every year or every other year!

[@MC-yb4jo]

Good summary of a closed marine cooling system. I see a lot of old boats without any strainers. This addition looks like common sense.

[@mitchellharvatin1739]

"Yup my elbow says 7.5 lbs of torque" Great video , please keep them coming! Very comprehensive 🤙🤙

[@JorgeSilberstein]

The symptom that my boat had before encountering this problem was that it was emitting white smoke from the exhausts. White smoke can be mistaken for condensation, but if it comes out when it's sunny or after a while, this might be the problem. Thank you very much, Ron, for the great explanation.

[@cindycunningham5769]

It is always a pleasure to listen to a guy who has obviously actually done, for decades I suspect, what he is talking about. Keep it up! Thanks

[@rontanis1024]

Thanks

[@felinanpuggy]

Many thanks , you are a very good teacher. A ton 23:00 of valuable information.

[@crgeorge1]

The video end before 23:00

[@kriskafowlski4463]

Fantastic video Ron. Thanks

[@eduardotapia6111]

Excelente gracias Ron! 🇲🇽 Mazatlán Sinaloa México!

[@eq6222]

Great video applies to boating in general, not just ski boats.

[@concretecurt]

Thanks for the comprehensive procedures for trouble shooting cooling systems, your expereience is invalueble.

[@wowchad]

Very good info here, thanks for putting together a stellar video! That’s coming from a guy who doesn’t even own an inboard ski boat. All the same info applies to performance BBC - Bravo Drive I/O applications, with a few minor differences.

[@tomhurstdrums]

Ron, you are fantastic! I’m a total noice owner of an 89’ Nautique 2001. Got in one season (about 12 days out last summer) with my boat and changed battery terminal leads, oil and the impeller once with minimal issues. Had the boat Winterized by a expert dealer here in Nashville and went to take her out the other day to blow out winterizing fluid (impeller was “new” from end of last season) and promptly overheated at the dock while idling. (Went up to 200 on thermostat within 2-3 minutes before I noticed as I was parking the truck and trailer.) 😫 Hoping I haven’t done a bunch of damage to the motor. Immediately shut it down and am now beginning the process of going back through the coming system to see what might be the issue from pulley bearings/impeller assembly, sea water strainer intake etc. Your thorough, thoughtful and incredibly informative approach gives me some semblance of hope that there’s hope for my neophyte ignorance yet. 🤪

[@rontanis1024]

Damage to the engine is highly unlikely, damage to the exhaust system is possible, fix the cooling issue then watch closely for muffler leaks where the hoses connect.

[@jamesharmon5963]

I really enjoy your videos. I love the older 70s and 80s ski boats. I plan on buying and restoring one in the future and your videos are very informative. Thanks for sharing your knowledge.

[@rontanis1024]

Thanks, taking requests for new subjects

[@lonniestevens7963]

My boat is fresh water only, Do I need a strainer?

[@lonniestevens7963]

Do you bump the motor to see what direction it turns?

[@rontanis1024]

@@lonniestevens7963 unless you run in a swimming pool I recommend a strainer, I have seen some pretty odd stuff in a strainer basket

[@lonniestevens7963]

@@rontanis1024 Thank Ron, getting one.

[@ambrosebruno220]

Thank you for sharing amazing knowledge to a new boat owner.

[@karenwilliams2232]

Thanks Ron, I ordered a strainer and fittings from you today! I'm restoring a Ski Supreme and it was removed and replaced with a hose fitting I'll feel better with this on. Maybe a video of the ventilation of owning an inboard ski boat. Thanks again Neil

[@lauramonroe9446]

Thank you! Awesome video!

[@SkypowerwithKarl]

One of the best investments a boat owner can have is a “boat wet exhaust temperature alarm”. When a strainer becomes clogged you still have a problem but now you can stop and correct it before it becomes expensive and wrecks the weekend. This alarm goes off way before any other symptoms or alarm. It’s save me and others several times. It’s a must for yucky water. The hardest part of the installation is mounting the indicator in the helm. One other thing, the through hull scoop you showed is the most common, but what really helps in some areas is the though hull that’s shaped like a wedge or door stop that has a plate with many little holes. It keeps the big stuff out and what does pile up on it is scrubbed off by the rushing water when the boat gets under way. You would figure theses things would be standard equipment for how much people pay for these boats.

[@rontanis1024]

I agree, today's boat builders have many options to add early warning sensors but they don't. heck most won't even install a sea water strainer. much less a water flow warning. Outboards have them. As for the wedge style intake that is up to the boat builder.. as they usually recess a mounting area in the hull mold.

[@SkypowerwithKarl]

I actually buy only the alarm panels. Amazon has an assortment kit of thermal switches with various temperatures, NO & NC. I have someone run the boat while I observe the temperatures around the hose under various conditions to establish a baseline for that engine/marinizing. I use a FLIR camera that attaches to my iPhone to determine temperatures and best position for switch placement on the hose. A thermal switch about 5 degrees over when measured in summer and 10 over in winter is selected. The idea is for the alarm to go off ASAP when something’s wrong and no false alarms. I use two stainless tie straps instead of two big hoses clamps to attach the switch. On generators I use a normally closed switch to break the ignition circuit. Boat manufacturers really have no excuse. On larger boats ABYC actually requires it now.

[@tomhurstdrums]

Thank you Karl. Is that something I can install even on an older 89’ Nautique 2001?

[@SkypowerwithKarl]

@@tomhurstdrums Absolutely. Probably even easier with less junk in the way. Just takes basic electrical knowledge, common sense and your favorite beverage to help ponder on the next step.

[@tomhurstdrums]

@@SkypowerwithKarl Well… that common sense part might be a challenge for this 🤡 here. 🤪 I ain’t the sharpest tool in the shed, but I sure appreciate your guidance none the less. Thank you my friend. (Hoping I haven’t ruined my boats 351 PCM overheating it at the dock the other day. 😫

[@richibmer]

Great video.. I'll be ordering a sea water strainer for my MasterCraft ProStar190 as we sometimes see trash on the lake after a storm. Quick question: 1996 ProStar190 Indmar Marine 350 TBI engine with 1050 hours. Starts fine, idles fine, runs fine at 32MPH and shows a steady reading of about 150 degrees. After shutoff the water temp zooms past 180 and even close to 200; sometimes enough to light the check engine light. New FB6-9 raw pump, replaced the circulating pump a couple of years ago. What I have noticed is - starboard exhaust manifold is hotter than the port side and I am also getting a small amount of water in the crankcase. I believe it's the starboard side exhaust manifold riser gasket, which is 28 years old. Still trying to get a good tool (need a Bondhus 5/16 swivel hex key wrench - on order) to get the 2 rear bolts off the manifold riser. I have the riser gasket and new screws on order. Any other thoughts?

[@dreamkatchersbandb]

Would have been interested to know what you found with the power steering cooler and the missing impeller rubber....hopefully not lodged in the hose en route....thank you for the strainer advice and it secures the one you use as the one that is better than the cheaper designs that people are having the cap blow off when hooking up garden hose and turning the water on for starting.

[@mikemackereth8719]

Great Video. I have had my boat over heat and melt the exhaust and rubber. Learned the hard way. I have replaced everything in this video. :( Where I kept my boat I change the pump every year do to sand getting in the intake. Love your videos. thanks.

[@glastronjohn1837]

Another great video. Having a sea water strainer is a good idea. Now to add one to my boat.

[@rontanis1024]

On a ski boat it's more important than an oil filter

[@pbgd3]

Curious as to the importance of the strainer. Thru hull skins, so does the trans cooler inlet screen. Does it reduce screen contamination?

[@rontanis1024]

@@pbgd3 Trans cooler is NOT a filter, it clogs up easy, the strainer is designed to filter the incoming cooling water with a large capacity screen, that is easy to clean.

[@antoinegauthier6349]

Finally a video that helped

[@Supanova70]

On closed cooling stern drive boats if you put to much concentrated antifreeze in will it overheat? All passages are clean new pump risers manifolds but temp is 170 this year ntead of 160. Stat is new too. 80 ocean. Thta`s the only thing i can think of. Also guage and sensor new too.

[@mcleodhomeservices]

Very informative as always! Thanks Ron!

[@rontanis1024]

Thanks, taking requests for new subjects

[@mcleodhomeservices]

Ron Tanis - Maybe a video on what would cause excessive vibration... Prop, shaft, cutlass bearing, engine mounts, engine probs, etc. Trying to figure out mine now. New ARE shaft, reconditioned prop, engine runs smoothly. Experiencing excessive vibration at ~ 700 - 2000 rpm.

[@zackarymartinez5472]

Thank you for the lesson

[@curtbareman3007]

Question for you about sucking up sand please. What's the best way to get sand out of the engine block on a 502. Backflushed everything but can't get it all out of the block.....Thanks

[@ProfessionalDad]

pulling my hair out on my 4.3 Penta. Replaced impeller, checked water pump. still overheats , wont seem to pull from sea water intake. backflushed the hose and it doesnt appear to have a hole or crack.

[@jmagana31]

New boat owner. You are awesome thanks. I have a 1990 Sanger. Doesn’t have the salt water filter and looks like the water goes first through the impeller and then into the oil cooler. Is that normal?

[@konakev1203]

Great knowledge! Thanks for the video

[@joelehtola10]

Hi Ron... Thanks for the video, it was super informative. I have a 1991 Ski Supreme 19 ft medalist with a 260 HP 5.7 Mercruiser engine and have been having an issue with the boat when it gets warmed up. The first three skiers, the boat runs great and has plenty of power. However after pulling skiers for about a half hour, the boat will lose power when trying to pull a skier up. It will pop and sputter through the carburetor an will not get up to speed. Sometimes if you can get the boat to plane out it will run fine for awhile but eventually will lose power. However it will idle just fine, even in gear. (we have had to get back to the landing that way a number of times.) The temp gauge shows about 160F all of this time so it seems like the engine is not overheating? However I was interested to find our that the the exhaust water is split off before it reaches the thermostat. I have not smelled any of the burning rubber or fiberglass like you described in the video ( am a familiar with both of this e smells) I will be checking some of the things that you pointed out in this video so see if they might be related to the problem. It does not have the inlet screen that you installed in this video so I will need to be adding it. I have a rebuild kit for the seawater pump on order and will be replacing it this week. Also, I will be checking the inlet to the trans cooler. (on my boat, the water goes through the seawater pump first and then to the trans cooler) My question is if you have run into anything like this in the past and may have some ideas on things I might be able to check out. Thanks in advance for your help. Joe

[@rontanis1024]

SOunds like the engine is starving for fuel, next time this happens crack the fuel fill cap open & see if a vacuum had formed in the tank, a clogged vent (dirt dobber) will cause this.

[@felipefuentes360]

Hello Ron I got a mercruiser 4.3 and water is coming into my power steering pump I see they have a power steering cooler can I just change that out and that will be fixed

[@derekgriesinger6273]

Really great video, good job!

[@kennonwerner8192]

Hello. Maybe you can help me out. I have the indmar 6.2 raptor 440 engine. I shredded an impeller to pieces and there are no pieces to be found in the impeller housing. How can I find or possibly back flush the pieces out. Thank you 🙏

[@rontanis1024]

I am not real familiar with the plumbing on the engine, but you can follow the discharge from the raw water pump removing each hose one at a time and inspect, flush as you go. I suspect you have a heat exchanger on that engine, and the engine block has coolant flowing through it and not seawater. That is a good thing as seawater cooled engines can trap impeller debris in the block passages.

[@kennonwerner8192]

@@rontanis1024 thanks for the response Ron, I’ll start with pulling the hoses apart but I suspect the pieces are trapped in the heat exchanger or somewhere.

[@marcorlvera6686]

Hi, one question, how long should the engine be on in neutral?

[@rontanis3732]

Not sure I understand the question, you can leave a ski boat motor in neutral at idle until it runs out of gas as long as it's getting proper cooling.

[@kamrynlindskov385]

Love this video! I have been having a horrible time with my pcm Chevy 350 direct drive motor. I ordered a strainer from you guys yesterday. Thinking about trying the raw water pump and impeller as a start. It won’t over heat until i am driving fast or pulling someone. Thoughts? Has a new circulating water pump installed last year. Keeps burning off belts like crazy.

[@BertLangdon]

Check for debris and obstructions in the cooling lines. And make sure there are no air leaks in them, either.

[@jorgemagana6544]

Can you help me find a correct Impeller...1990 Mercruiser. 5.7 liter .. bluewater inboard

[@scottliesch]

Great video!! One question for you. Would this strainer help with filtering sand? I sucked about a half gallon of sand into my ski boat this past weekend trashing the Johnson impeller and plugging every hose from the thermostat to the water pickup.

[@derekgriesinger6273]

depending on the size of "sand" granules, the strainer is not likely to capture smaller particles.

[@ranamahmood1992]

My boat has the raw water strainer installed just like you said it should be. What are your thoughts on installing a second strainer after the raw water pump and before the next cooler? It seems like it would make it easier to locate broken impeller veins should they travel down stream. …or would it be better to just let the cooler catch broken pieces?

[@rontanis1024]

Not sure I would want a strainer on the pressure side of the pump, I would need to experiment with that, I like the thought though.

[@georgea0731]

Thanks for explain the system and showing how to do an impeller. Mine is leaking water, so I need to do the rebuild kit or order a new one on a Northstar 6.0L Engine. BTW do you know where the oil sending unit is on this Cadillac engine. It's not like the tradition Oil sending units.

[@rontanis1024]

Is this a modular pump? raw water pump? circulation pump? We don't see many of these in our shop, and sure where the oil pres. sender is, but the water temp sender in behind cyl 8, not in the intake.

[@craiglittle3861]

My boyfriend has a 496 mag bravo outdrive. I have had to remove debris from my motor more than once. I’m now looking at installing a thru hull with a strainer. My question is my stock raw water pump is a pain to change the impeller. Has anyone ever changed the pump to a type on this boat (PCM)?

[@rontanis1024]

If you have the room in front of the engine I would rather use the Johnson style crank driven pump, like on the Indmars, look to see if your lower pulleys have 3 bolt hole drilled & tapped for the bolts.

[@canavyvet]

Fantastic video, thank you

[@hessman5198]

I have a 2001 Indmar ltr 330 overheating issue. Strainer is clean, I replaced a good impeller with a brand new one, installed a new thermostat and the boat is still overheating. I'm thinking the only thing left is the circulating pump which does have a squeaking noise, am I correct or am I missing something? Thanks.

[@rontanis1024]

The circulating pump does very little in a ski boat other than a convenient pulley for driving the alt. etc. have you ever shredded an impeller? the missing rubber blades can lodge in themselves in bad places

[@hessman5198]

@@rontanis1024 not in a few years. I also installed a new trans cooler back in the spring. The boat ran fine until last week.

[@rontanis1024]

@@hessman5198 Strainer bowl tight with o-ring type gasket in place? if a raw water pump is sucking air it can greatly reduce the pumping capacity.

[@hessman5198]

@@rontanis1024 I don't remember seeing an oring and I did notice a little water dripping from around the top of the bowl. Thank you.

[@stankthetank9375]

Would this be the same install and service for a Marlin ski boat with a 5.7 mercruiser direct drive as well.

[@rontanis1024]

same principals

[@ansongray5171]

Great video. Any possibility of you doing one on vapor lock? About ready to kill my Mercruiser 6.2

[@jasony9950]

Join the club haha. Same issue. Try non-ethanol gas, make sure gas vent is clear add more venting to engine compartment, prop engine lid if needed and keep exhaust fan running the whole day

[@Inspectorjb]

Ron, how did you get the engine filled back up with water? Thanks.

[@rontanis1024]

Put all the plugs back in, hoses connected & start the engine in the water, the raw water pump will suck water from the lake & fill the engine.

[@drivewaygarage1561]

Great video

[@kmatusik73]

what about a stern drive in salt water? should I add a Strainer?

[@rontanis1024]

Strainers have the most benefit if they are before the raw water pump, on alpha drives this is not possible, on Bravo drives with an engine mounted water pump you could mount our in-line strainer and get the same benefits that a typical ski boat engine does.

[@Den-tx1ml]

Hello, is it possible to back wash cooling system on MerCruiser 350?

[@rontanis1024]

Back-wash or flush?? Most want to flush the engine after running in saltwater, and yes this can be done. Back-washing to try to remove stuck debris is not so easy, each section needs to be isolated and back flushed, if there are impeller blades broken off & stuck in passages, good luck, I have seen several stuck/wedged in the cylinder heads that would not come out from any back-flushing.

[@halla1968]

I need to check if my boat has one. If not I will order one

[@eduardojavierjuarezsantos3099]

How can i have comunication with you for see some prives about Water pump??

[@rontanis1024]

[e-mail]

[@eduardojavierjuarezsantos3099]

Thanks i Will check, thanks again

[@eduardojavierjuarezsantos3099]

I almost done to see al your videos so are very interesting nice videos nisce tutorial

[@NDLAP66]

Hello, I accidentally left the intake and exit hoses off the impeller housing and ran the engine for a short while with dog ears on the out drive. smelled and saw a little smoke and that putrid smell. should I now change the muffler and hoses from the riser?

[@rontanis1024]

Not sure what a little while is, but if you smell burning rubber you have damaged the hose and it probably needs to be replaced

[@daynerochon9365]

👍🏼👍🏼👍🏼👍🏼

[@sunyang-shenhaiyuwei]

Hello, I am a friend from China. I hope to get in touch with you by email so that we can exchange some questions about water boating. Looking forward to your reply

[@nfaproductions83]

Hey Ron! What happens when you purchase a ski boat and there's NO impeller blades left to measure the "diameter" haha asking for a friend 🫣

[@Boatordie]

I have an old 2002 Ski Nautique. What could I replace the muffler with? Stainless steel option? "fresh air" option?