Spark Plugs Must be Changed Annually???

On page 53 of the Indmar manual there is a Scheduled Maintenance Chart listing when things need to be checked, and when they need to be replaced.

Note that Spark Plugs are marked as Replace every 300 hours or Annually whichever happens first.


So Indmar/Malibu engines use AC Delco 41-932 Platinum plugs.


These plugs are rated for 100,000 miles for a car or truck. Why does that mean annually in our Malibu boats?


So i have to ask do you change your spark plugs every year?????

Nope, no need to. I know guys pushing 800 hours on the orignal set of plugs.

I change every 2-3 years which works out to about every 300 hours.

Not that you asked but if you do change them, best to do it in the spring after you have run it once or twice. Putting fog oil on fresh plugs in Fall is not the best plan.

indmar/malibu got a discuont from their spark plug provider to put that in there.

If you didn't change the spark plugs annually would it affect the engine warranty?

Thanks for the tip AtTheLake, I did not know that. Makes sense.

Gary, interesting question. I don't know how strict they are on that stuff. Technically if you read the last few pages of the Indmar manual it also says any service work not performed by an Indmar authorized dealer voids the warranty.

I have a hard time believing they enforce that. Voiding the engine warranty for changing your own oil or something routine maintenance seems wrong to me.

Anyone have any personally experiences in dealing with Indmar w/o having the service records from a dealer?

Anyone have any personally experiences of your dealer giving you a hard time because you do the maintenance yourself instead of bring the boat to them. Thinking about when i need warranty work for the next 2 years....

1, spark plugs will not last a 100 thousand miles like the auto dealer tells you. you start to loose mileage and power. it then stresses you coil overs and coil overs start going out, it will also stress your coil packs. plugs are cheap and everyone can gap a plug and install them the gap is on the engine cover. 2. I have never seen a warranty void for non maintenance. other than the oil never changed. usually any failure has happen to many other customer's What I have seen in the industry is you can get anything warranty except for freezing. as long as its within the warranty period and after warrant I seen them pay for parts way beyond the call of duty Joe

annually is different for everyone I have seen many 10 year old boats with less than 100 hours and I have seen boats 2 years old with 450 hours. I do not believe in fogging an engine that was great when you had a carb. the new engines are fuel injected with many sensors, you also gum up you throttle body which effects you idle and idle air control. they are also now using o2 sensors, cats, exhaust temp sensors,cat's they will soon be using maff sensors instead of map sensors say good buy to these items. the cat will over heat and never function O2 sensors will not function properly . If you really need to use fogging oil spray a little in each cylinder. And talk about warranty when they find out these engines are being fogged then things will probably change. Joe

are you sure plugs dont last 100k miles? cause my dads ford ranger has 195k miles on it with the original plugs. the only reason though is cause they are the biggest pita to change.

I am a ford tech check the gap you will see if the coil overs start to go they will cost you 600 dollars plus labor. (if it has coil overs)it may have coil packs I don't know what year it is. change the plugs you will be shocked at the power difference. usually the HC are so high it won't pass emission. Joe

it passes emission, barely probably though. the truck is a 99 and my dad plans to drive it til it dies so he isnt even going to bother spending any more money on it.

Things are going to change in the industry due to the new High tech engines and the emission's standard's in calif. is setting. they are going to make the e.c.u. go into limp mode when there is a failure. right now you can use it till you feel like fixing it. Once they start using the o2 sensor's they will start mounting them pre and post to check the cat efficiency. Joe

I am not saying you can't leave the plugs in for ever. you could find many people prove me wrong I am just trying to save money in the long run and get the best performance on the water. and 1999 was a different time simpler,great they just keep tighten up on emission's that why jeep got rid of there jeep 4.0 a proven engine, dodge cummins straight six proven. its all about emission's and I see the boat industry heading that way. all with these changes comes a very efficient engine, great torque and performance. coil over sequential fuel injection instead of batch fire this fly by wire throttle body is very unnecessary. their isn't any benefit emission wise or performance wise just another part to fail from moisture. Joe

Joe - good points. You talked me out of fogging through the throttle body.

I used to fill the gas with a very light mix (1/200) of 2 stroke oil to apply a thin coat of oil on all things the gas would come in contact and to coat the valves and cylinders when storing. Good or Bad idea?

if it doesn't have a cat it will not hurt it. Joe

A mechanic told me that my VLX is way overdue for a tune up and that I could damage the engine if I kept using it by possibly cracking a head or something. My boat has the Indmar Monsoon and has about 280 hours on it. He also said that the plugs were about $40 a piece. Is this true? Why would the plugs be that much higher if the engine is basically the same as a car engine?

175k on my original plugs in my car

I would be more concerned about them getting stuck in the block in the humid enviroment. I plan on going 3 years

But Than the Indmar manual also requires you change the impeller every two years, which most people change them every year religiously... Oh well. But Id keep the plugs three years minimum before swaping them

Changing plugs anually is cheap insurance. I like to look at them after every season to determine how the engine is running. I think the last time I bought plugs from NAPA they were about $6.00 each. I add a squirt of fogging oil into every cylinder and I make sure I coat the threads with it to prevent corrosion before installing the new plug. When you re-insert the block drain plugs, use some anti-sieze compound on the threads to help yourself the next season. I change impellers in the spring.

The more time you spend with your engine on regular maintenance, the better you will be able to detect minor problems before they become costly or leave you stranded. Weekends are priceless...

I would stay away from that mechanic. first off a tune up consist of very little. plugs, their are no distributors any more some have plug wires some have coil overs. no points no rotor. How would plugs cause any damage to the engine total impossible. the only way to crack a head is extreme heat or freezing. the heads are cast except for the Lt1 or Ls1 they are aluminum and reverse cooled so they are very easy to over heat. there isn't any parts to replace. the ignition mod is in the ecu it recieve"s signal's from the crank sensor, Cam sensor,tps, air intake temp, map sensor temp sensor and exhaust temp sensor or now 02 sensors. plugs are 40.00 for a whole set, the different's between marine and auto is marine are SS, auto will rust a little who cares! Napa also carries marine plugs. Joe

Karl You said it MY TIME ON THE WATER IS PRICELESS. I spend so much time on customer boats in the summer I don't understand why they own them. I just came back from a whole day of glass 88 degree's You can't put a price on that. even if plugs were 40.00 each if it meant I would have a trouble free day it's worth it.Our season is may- oct. 1 if you are lucky. I did not have one break down. only thing I had was a couple vapor locks which cost about five minutes on the water I do have a fix for that for nex't summer. my boats a 1999. Joe