How frequent should i change my plugs? 98 drag motors

[turbo408]

I have twin 98 mariner drag motors and I was curious how often should I change my plugs. Motors are running great but have 80 hours on them. I was wandering if I could gradually be losing power and maybe not noticing it.

Thanks

[hosejockey4506]

i was always told 60 or so hours on a hiperf motor is about all your gonna get probally time for a rering.

[StratosVT]

The way I look at it, plugs are fairly cheap so I change them quite often. If you use the NGK BR9HS plugs, they're about $1.50 at O'reilly's. At that rate, you may as well change them a few times a year. If you use Iridiums, I think they're like $7-8 bucks apiece so might not change as often.
I view gear lube changes the same way. Merc hi performance gear lube is about $10 per quart. IMO, it's cheap insurance to change it often. The more frequently you change it, the more likely you will be to catch leaky seals or other problems before they destroy your gearcase. Just my opinion.:)

[Jay Smith]

Turbo,

IMO It would be according to how much time the motors are normally running, turning well above ideling RPMs as running an engine at the lower rpms is when a plug tends to load up and oil and or gas fowl needing changing.. Time idling, what brand and make 2 cycle oil and its make up be it either petrolium/syn oil and at what ratio are you mixing would also be a determining factor as to when a plug reduced its performance and needs to be changed also. If a motor is ran in the mid and higher rpm ranges most of its life the plugs should live longer than one that is idled quite a bit thats a no brainer. To say a specific time line or hours ran to a plug change should be determined as the service its in demands and if performance of the plug/motor deminishes...

Also we are seeing the recreational Hi Performance motors with the use of a good grade of oil in the correct ratios,and "normal" use NOT ABUSE going 140 ish hours before the leak down tests point to a high enough leakage that a rering job should be considered...

The OEM plug that Mercury installs in the Drags are the NGK BUZHW, in race engines I have also had good luck with the ( Irid.configuration ) Denso 1WF24 or NGK BR9HIX they tend to recover well from an idle to the line to a snap open of the throttle without that momentary hesitation that some of the plugs seems to experiance...

good luck,

[turbo408]

I bought the boat with 57hours on one engine and 3 hours on the other with a top pin. I usually cruise around 4200 and haven't pushed it above 8300rpm. I have since took your advice on the fuel filter situation and am correcting it now. I run the quicksilver synthetic blend a 32:1. The heads have milled combustion chambers on the 26cc heads and on one i am seeing 157 cranking and 145 cranking on the other but visibly checking one has thicker head gaskets, which i expect the rebuilder installed. I would like them to both be the same. Whats your input?

[150aintenuff]

1 change plugs atleast a minimum of once each season
2 buy 2 sets of the equal thickness head gaskets and install so ya know they are both right..... and at 26CC your compression should be a bit higher than 145........ ya better do a leak down IMO......

[Jay Smith]

Turbo,
I agree with Nick, using a true 26 CC combustion chambered head installed on a healthy engine , even with the thickest gasket I know off ( 1.5 MM champ motor) even if it was modified with high the port timing the engine should yeild more compression than you sited. I'd take Nick's advise and leak that puppy down. Again I'm a stickler for equalized - system matched things I'd see if I could'nt pick up a set of stock CC'ed OEM used heads and install or have them cut to a nominal 34 CC and use a stock common 44 series 1.0 MM head gasket and yeild 140 ish cranking compression, this is safe at sea level and the timing set at a normal 25 degress... With you not knowing the true CC ( by checking with a fluid burett ) your kind in the dark and assuming...

Good luck,

[stoker2001]

I have twin 98 mariner drag motors and I was curious how often should I change my plugs. Motors are running great but have 80 hours on them. I was wandering if I could gradually be losing power and maybe not noticing it.

Thanks
Any chance this is a DCB mach22 that was advertised on ebay this year?

[turbo408]

Yes it was listed on ebay this year but did not sell. I contacted the seller and agreed to he asking price. I think it was a really great deal. I have not been disappointed yet. Boat runs great. I have never ran it by myself yet. It has 26"pitch et's on it for acceleration. They also work great with 4 people 2 full ice chest and 50 gallon of fuel it will run 101 on gps @ 7700 rpm with absolutly no fast boating experience. This is my first boat. I love it no porposing it handles great and takes rough water like a champ for a shallow hull. I was told it will run 112@9200 with driver and light load.

Without a doubt this is the best boat I have ever rode in as far at ride and usuable space for the size.

[150aintenuff]

Turbo,
I agree with Nick,

that wont happen again..... quick freeze this moment in time.......... thanks Jay

[Jay Smith]

Ah Nick , I agree with alot you say ....:cool: Well maybe some of what you say ;)

Just kidding,

Love,
Jay

[150aintenuff]

Ah Nick , I agree with alot you say ....:cool: Well maybe some of what you say ;)

Just kidding,

Love,
Jay

LOL its all good....... maybe in 2008 we will once again agree... or would that be 2009..

[stoker2001]

Yes it was listed on ebay this year but did not sell. I contacted the seller and agreed to he asking price. I think it was a really great deal. I have not been disappointed yet. Boat runs great. I have never ran it by myself yet. It has 26"pitch et's on it for acceleration. They also work great with 4 people 2 full ice chest and 50 gallon of fuel it will run 101 on gps @ 7700 rpm with absolutly no fast boating experience. This is my first boat. I love it no porposing it handles great and takes rough water like a champ for a shallow hull. I was told it will run 112@9200 with driver and light load.

Without a doubt this is the best boat I have ever rode in as far at ride and usuable space for the size.
I have rode in this rocket before as you bought it off my good buddy Don Mehlng (i dont think don posts here).I have no doubt it will run 112 with the 26ETs.If you ever get the itch,it will go 120+ with some 30+ pitch wheels.You got a smoking deal on it
Have fun and be safe

[stoker2001]

I bought the boat with 57hours on one engine and 3 hours on the other with a top pin. I usually cruise around 4200 and haven't pushed it above 8300rpm. I have since took your advice on the fuel filter situation and am correcting it now. I run the quicksilver synthetic blend a 32:1. The heads have milled combustion chambers on the 26cc heads and on one i am seeing 157 cranking and 145 cranking on the other but visibly checking one has thicker head gaskets, which i expect the rebuilder installed. I would like them to both be the same. Whats your input?
Turbo
Don detuned the motors with 30cc or so heads so he could run Av 100 with some pump gas.The Original stock 26cc drag heads will come in around 180psi cranking and i have seen guys get away with straight 100LL AV gas if the tune up is mild
Good luck