coil question
 

Could a bad coil cause an engine not to rev past 5000 rpm.Motors run great till I hit 5000 and then I see one motor has a bounce in the tack and both motors wont run past the 5000 point even with different props.These motors ran to 6000 on the dyno and the only thing I changed is the coil.I also checked fuel supply and 5 psi at max rpm and O2 sensor says they are running 10.8 afr.

Thanks Nordic95

Re: coil question
 

The boat have a rev limiter in it? Mine at 10.8/10.9 A/F left the plugs DARK brown. Might want to take out a little jet.
It's also unlikely that BOTH coils have the same problem.

Re: coil question
 

no rev limiter,they are still sitting on my work bench,so I rule them out.AFR dropt to 10 .8 at wot only,runs around 11.5 to 12.0 all other rpms.I think one coil may be the culprit and lugging other engine down with it.Both motors run perfect up to the 5000 mark.Dont understand,very weird.

Thanks Nordic95

Re: coil question
 

ttt

Re: coil question
 

if you suspect the coil(s) then swap them out. No biggy. CanDo

Re: coil question
 

I would say yes.
I had that problem in Lake George. Tach was bouncing back from 5000-4800rpm. Thought it may have been the tach,found out in LG was the coil. Motor died out in the first leg of the run.
I have had 2 MSD Blaster coils go down on me in the last 40hrs on my boat! I now have a spare on board.

Re: coil question
 

MSD tech recommended this coil for marine use. http://www.msdignition.com/coil_blaster_3_8222.htm

Epoxy filled and can be mounted in any position.

Re: coil question
 

If I was to use this with the stock Thunderbolt IV set up will a ballast resistor be necessary??

Re: coil question
 

http://www.msdignition.com/pdf/8202_...3_frm22698.pdf

If you have a ballast resistor now, then I believe you would keep it.

Re: coil question
 

Tx for the info.
I will switch to those if I keep having problems.
Both coils had made in Mexico stickers on the bottom. :rolleyes:

Re: coil question
 

I had a stock tb 4 when I dynoed the engines.I ran the marine MSD coils with those distrb. and it worked great.I then change out the ditribs for the MSD ones and used the same coil with them.No ballast resister on either system.

Re: coil question
 

I have been running the MSD coil with out resistor on a thunderbolt IV with no problems.

Re: coil question
 

I Have Another Problem, Can You Lay The Coil On Its Side? Out For My First Run Today And Turned The Motor Of To Check Everything Only To Findout Now No Spark On A Restart. 20 Minutes Later She Gets Spark And Runs Only To Do It Again After A Shut Down To Check To See If It Will Restart And Again No Spark? What Gives? Called Msd And They Advised To Stand The Coil Up If Its An Oil Filled Coil. Possible Thunderbolt Module Trouble ?