Can anyone give me advice.I am running a k&b 7.5 cc(.45)outboard motor.I use 60% nitro,what glow plug should I use.At this stage only OS glow plugs is available?need help?

OS plugs are a bit more expensive than most, I would look into mail ordering other kinds.

RCU Engine Forums would have just about any type of question about them, just do a search on glow plugs and you'll get pages of questions and answers. Look for the search button at the bottom of the page in any forum. [8D]

Back to your question though, 60% your going to need a cold plug. I dont think anything under that will hold up.

If your blowing cold plugs then I would suggest adding a shim under the cylinder head. High nitro needs a lower compression ratio than a stock factory clearance, or you'll have problems holding plugs.

Here's the OS Plug chart from their website. What number are you using?

This webpage will help also, just click on it [link=http://www.scootworks.com/rdrc/gloplugs.html]here.[/link]

I would reconmend running theres,O.S,R5,A5,,,,MC Coy#9..... the way I read on some threads and tech notes,if your running30+nitro you need to run a cooler plug... On my CMB.21RS Redhead I'm running 33% and had a Mc Coy#9 and lasted 6 runs.That good in my book. My O.S #8 only lasted maybe 2 to 3 runs.Then I'd found out the info about running cooler plugs..[8D].. Some of the guys that I'd talked to are running Mc Coy#9.

Thanx u guys for the help ,I apreciate it

Another brand is Novarossi plugs - I've got N. 5 for 65% - on the back of the glow plug package the chart (for cold plugs section) lists:
N. 5 Cold Plug
N. 6 Cold Plug
N. 7 Very Cold
N. 8 Very Cold
N. 9 Cold-Special

I havent had a chance to try the colder ones (6-9) as my used boat came w/a bunch of plugs.

I added a good reference sheet to my photobucket album that you might find handy

Here is the [link=http://i231.photobucket.com/albums/ee247/jetpack_photos/Boards/ReadingGlowPlugsandHeads.jpg]link.[/link] It is too large to post here.

Running that high of nitro requires watching the head clearance as much as watching the plug. Once you have it sorted out, you shouldnt have to worry too much on them burning out on you, and be able to hang on to your spares a bit longer.[sm=thumbup.gif]