Crossflow V6 spark problem - help needed...

[Steve2ManyBoats]

Seems I've been posting here for help a lot lately - everything's been fighting with me. Here's the latest situation and problem.

Picked up a low hour 1979 V6 crossflow 235. Really nice shape. No obcious problems. Taken off a boat running. Been sitting for years. dry compression is exactly 110 lbs per cylinder. Carbs fouled/varnished so I cleaned/rebuilt them.

Engine won't fire. No/insufficient spark is the problem now. You can get a weak spark at each plug, held to a ground, but not enough spark to power an inductive light and apparently not enough to fire, even on a shot of ether.

Seems like the two powerpacks are OK since all six plugs get a regular, weak spark. Can't time it though because the spark is too weak to fire the timing light. Without replacing all the components, anyone got an idea what the most likley candidate is and how to diagnose it (like with a VOM)?

I was thinking stator, but would like to hear from any of the pros here.

Thanks again guys for the help.

Steve.

[dynobo]

If you have weak spark you could have a bad stator but probably just not spinning it over fast enough. Pull all the plugs out and spin it over and see if the increased rpm causes a better spark. You can do ohms readings but, I never bother anymore just much easier to connect DVA/PEAK READING METER and see the real picture.

[SlimDaddy]

If I remember correctly the CD ignition has to spin at least 250-300 RPM in order to build up satisfactory voltage for the capacitive discharge.I had a battery go downhill on me and it would turn over but not fast enough to fire the motor.:cool:

[Steve2ManyBoats]

I'll pull the plugs and see if spinning faster will make produce a better spark. However, the battery I'm starting it with is very strong (with a back-up charger on it) and it's spinning the V6 as fast as my V4 crossflow spins.

The OMC manual says that the spark @ 300 RPM should be able to jump a 7/16" gap. No way my ignition is anywhere close to that kind of output. The manual also references a magical test light for the stator but offers no OHM or voltage readings. Anyone know what readings/outputs should be?

Also, I got a 91 150 V6 crossflow with a broken crank as a package deal with this motor. Ignition was supposed to be working well until the crank broke. Oddly, the motor still turns over by hand, just with a very wobbly top of the crank. Usually when cranks break, worse things follow...like "ventilated" blocks.

Since the 91 has 1 powerpack and the 79 has 2, obviously the two systems are different. It looks like the coils might swap. How about the stator and trigger?

Would there be any merit to swapping on the whole ignition system from the 91 onto the 79? Are later 1 pack systems better/more reliable than earlier 2 pack systems?

Looking for the easiest/cheapest way to get a running motor out of the parts I have on hand. The more I think about it, the more I'm concluding that the stator is the problem.

If swapping the 91 ignition would only be creating more problems, anyone got a good stator that'll fit a 79 V6 235?

Thanks...Steve.

[bigbore]

there's an ignition problem,do an ignition output test,service manual-omc's:cool:

[SportJ-US-1]

If all cylinders have weak spark, then it is probably the stator or a dirty connection between the stator and the boxes or a bad ground. A switch box will usually only kill half the cylinders and the likelihood of both boxes breaking the same way is too low to consider as is the idea of 6 bad coils.

[bw1969]

I've had a flywheel go bad on a crossflow (magnets weakened). If your 91 has a 9 amp charging system you might be able to swap out some parts. If the 91 flywheel has vents in it it is a 35 amp system.

[Steve2ManyBoats]

...so I guess that means it has a 35 amp charging system. If so, can I just swap the 91 flywheel onto the 79 and its 12 amp stator or will the magnets on the 35 amp flywheel cook the 12 amp stator?

Thanks...Steve.

[EMDSAPMGR]

They made both the 60 and 90 degree crossflow 150's in 1991. Also, the 150 crossflow came in two versions, the low amp alternator and the 35 amp. Assuming the 91 is a crossflow, you should be ok. Either way, you will need to change/swap all the electrical components, as the connectors may not match up to the old components. The 91 has a water cooled voltage regulator which will need to be mounted under the flywheel in the top of the crankcase in place of the existing cover. The 91 has only one power pack, unlike the 79. The biggest difference is that the 91 pack may have a built in rev limiter, unlike the unlimited packs that were standard on the old 235. The newer pack limiter is probably 5800. Also, it should have the cold start feature. Possible that your old block does not have tapped bosses to mount the newer power pack. You need to be sure the newer pack is well grounded. I believe your goal is to swap for the newer stator to improve spark. If the 91 is the 150S model, it will have the vented flywheel and the heavy duty stator. You need to match (swap) both the vented flywheel with the heavy duty stator.

[YELLOWSS]

make sure all conections are clean and tight. specially the grounds!!!! i have had ground troubles with all outboards. mercury efi's have more grounds than cars. i also had a v4 cross flow that had intermitten, and weak spark. it was a bad key switch. it took for ever to find.
good luck
Roy

[bw1969]

I don't believe a 60 degree x-flow ever existed. If your flywheel is vented it is the 35 amp system, you will have to swap over the entire electrical system.

[Steve2ManyBoats]

I'm pretty sure they never made a 60 edgree crossflow either. Anyway...

I tried to bypass the keyswitch by hotwiring right to the wire block to make sure it's not a key/harness problem - no difference. I'm thinking that either the flywheel or the stator or both are the problem. I'm trying to score a flywheel and a stator (if anyone has a working set that they're trying to unload for a fair price, let me know), but if not, I'll probably swap on the 91 ignition system.

Thanks again to all who posted...and if you have the parts I need, please let me know.

Thanks...Steve.

[EMDSAPMGR]

I believe my opening statement has been mis-read and caused some confusion, let me repost my opening sentence which hopefully will clear up any misunderstanding: They made both the 60 and 90 degree 150's in 1991. (The 60 is a looper, the 90 is the crossflow.)

[76baja18ft]

They made both the 60 and 90 degree crossflow 150's in 1991. .
nothing there to mis read.....

[76baja18ft]

unplug the big red plug from the wiring harness.. and then short across the starter solenoid and see if the spark is stronger....make sure you have all the plugs out when you try this because if it was to start.. you couldnt kill it easily...this takes the control box out of the problem..

[wideglide55]

I agree about the big red plug,my V-8 would shut off and not turn over or anything. Open that plug and use a small wire brush to clean inside the holes and the prongs.Might be all that is wrong.

[Steve2ManyBoats]

Tried unplugging the red plug - no change, spark still weak. Tried running a jumper wire to the hot wire on the junction block, too - no difference.

I still think the problem is either the stator or trigger or both. I stripped the supposedly functional 91 crossflow 150 ignition system (incl water cooled voltage reg and 35 amp flywheel.) Quick job - 20 mins. I also stripped the ignition off the 79. The flywheel off the 79 looked fine inside - no damaged or loose magnets. Stator looked fine too - no melted or damaged insulation.

I'm planning to complete the swap this AM. We'll see what happens.

Thanks...Steve.

[SwatDawg]

Seems this is common, I'm doing the same thing. I have a 88 GT150 witch was running fine untill one of the stator bolts backed out and chewed a magnet in the flywheel, causing it to get dislodged, thus knocking out stator. I'm changing the ignition from a 91 to this 88. the 88 has the 35amp, and the 91 does not. Changing everything, so it should work. Please keep me updated with your progress.

[davepnola]

Just went through the same deal on 83 crossflow 200 ! This is what I found , cut the black yellow stripe wire on both powerpacks and spin it over and see what ya got !! I had a short to ground on the ign kill wire (black yellow stripe) in the engine part of the harness !!

[Steve2ManyBoats]

I'm getting spark, it's just too weak to fire the motor. Both powerpacks are firing all the coils, just too weak to fire the motor. Too weak to even fire atiming light. Never got the chance to install the 91 ignition system today. Hopefully tomorrow.

Thanks...Steve.

[davepnola]

Yeah my spark was weak to, but the short to ground on this wire was not 100% , Do this take your test light clamp the the ground side on 12 volts and then check the black and yellow wire , see if it is grounded ? if not the check brown wire and brown yellow wire comming from the stator to the coil packs check them accross with a dvom and crank the motor, you should have trigger pulse of 100 volts or better I think it should be 130volts ac of course ! I had 90 volts spinning and thought it was the stator ,but it actually was the harness (with resistance grounding the kill wire , after i cut the wires for test purpose only , I had 130 volts coming from stator and good spark ............. good luck Davepnola

[Steve2ManyBoats]

Swapped in the complete 91 ignition system with the 35 amp alternator. After some coaxing, it came to life. Very, very stout sounding. Nice quiet bearings. Ran it up to operating temp for about 20 mins on the stand/hose.

Right now, it's set up stock with 61 jets.

Only problem left is that it's really hard to start. I cleaned the carbs and adjusted the floats. The carbs seem to fill and draw OK, but a short blip of the choke (this is an older motor with choke plates) causes the carbs to drip fuel. Is this normal for this engine? Should I adjust the choke plates to only partly close so the carbs don't draw so much fuel?

Also, I'm finding this motor very hard to time. Both this motor and my crossflow V4 don't seem to want to fire my timing light. Never had that problem with all the inline 4, inline 6 and V6 Mercs I've owned, just these two crossflow motors. Is this normal? Do I need to get a more sensitive timing light?

Once started, the 235 idles down very nicely and doesn't seem to load up. Blip the throttle and it responds instantly. I think the tune is close, I just need to get it to start better,

Thanks to everyone for your advice and help. This is a great board.

Steve.

[dynobo]

The choke blades closing is a good thing. Those old crossflows with the choke "flappers" are very cold natured. Sometimes takes a few minutes to get where they will even run.Make sure you have fuel to the carbs and trim the motor all the way down. If it spins over decent it should crank off fairly quick. Getting it to stay running is sometimes a chore.

Davenpola, stator should be DC current not AC.