1998 force 75 hp Stator

[kywings]

I have a miss at higher RPMs. Also lost RPMs ove the past few month. About 600-700 rpms. Ordering a DVA Adapter but only getting 465-470 ohms resistance. Could this be the cause? No Charging issues at all.

 

[pnwboat]

Re: 1998 force 75 hp Stator

Make sure you disconnect the stator leads before you measure the resistance. If the stator is the original stator from the manufacturer, then it should be reading 500 - 700 OHMs. Not saying that this is gospel for all 75HP stators of this type but usually they read in the mid to higher 600 OHMs range. I would suspect that the stator may be bad, or at least marginal. Checking stator output voltage is a good way to confirm.

This is an OEM stator. Notice the windings are sealed in either a red or black plastic like material. You cannot see the windings.




If the stator is a CDI Electronics after market replacement, then it should read 400 - 600 OHMS. If this is the case then your stator is probably OK.

This is a CDI Electronics unit. Notice that the winding are exposed.

 

[kywings]

Re: 1998 force 75 hp Stator

I'll have to take a look. From previous work I'm thinking the windings are exposed. If CDI that's good wont have to buy one just keep troubleshooting. I'll post results by the weekend.

Thanks for the response.

 

[Jiggz]

Re: 1998 force 75 hp Stator

Misses at higher RPM are more likely attributed to the trigger rather than the stator. Or it could also be one of the modules. This is with the assumption all the fuel related causes have been eliminated totally. And the only reason it is more likely the trigger is because the trigger dynamically moves physically with rpm changes for timing purposes. A stator generating power at low and medium rpm will most likely sustain the same power generation at high rpm. RPM increase doesn't necessarily increase voltage generated but more on frequency thus putting more work on the modules. You might want to inspect the trigger also.

 

[pnwboat]

Re: 1998 force 75 hp Stator

Make sure all the ignition ground wires are making good contact. There is a ground wire that runs from the coil mounting plate to the engine block. Make sure it's making good contact on both ends. Unplug all of the 4 pin modular connectors attached to the CDM modules (coil packs) and re-seat them. Reseat the bullet connectors from the stator and trigger.

Like Jiggz mentioned...you may want to check your fuel pump diaphragm if you haven't already done so. Maybe the motor is starved for gas at higher RPMs??? You can try squeezing the primer bulb at WOT and see if that has any affect. If it does, then definitely replace the diaphragm.

 

[kywings]

Re: 1998 force 75 hp Stator

I appreciate all the suggestions. Thanks to this site I started at the pickup tube and replaced everything to the carb. New Reeds 20 months ago. Cleaned Carb. Replaced check valves for fuel recirc. Swapped out all 3 CDM's with friend who has same motor that runs well. New plugs. Based on other posts I ordered all new Mercury connectors for ignition. Existing connectors were black and very dirty. Will install this weekend and check stator visually. Connector cases almost looked burnt. 20 amp fuse was also replaced. It was melted really bad but still worked? If you can imagine.

Is there a trigger check without DVA. I can improve miss at WOT by pulling throttle back slow no more than 1/8" without loosing RPM's. Just improve not eliminate.

 

[pnwboat]

Re: 1998 force 75 hp Stator

Check for vacuum leaks around the carburetor adapters where they are bolted to the block. Make sure all the bolts are tight and gaskets aren't leaking. Also check for leaks around each of the 4 by-pass covers. Each one has a gasket. There is a vacuum balance hose that goes between the base of each carburetor. Make sure no leaks there too.

Those barrel connectors on the yellow battery charge leads seem to get blackened on a lot of the 1995 and later motors. Looks like they aren't heavy enough to carry the current and looked charred. I replace the barrel connectors on the yellow battery charge leads with soldered/crimped spade lug connectors and added a 4 position terminal block. Use two positions for the battery charge leads, 1 for the 12VDC to the harness, and 1 for the tach wire. Never had any signs of overheated wires since I've been using this method.

The trigger on the CDM ignition system uses a Hall Effect sensor for each cylinder. You cannot check resistance. It reads open. I have experimented and found that if you set you meter on the diode setting, and get the meter leads oriented correctly on the trigger wires, and pass a magnet around the inner circumference of the trigger, you can trigger a diode reading when the magnet passes by the sensor connected to the wires that you're attached to. I haven't tried testing the trigger on the motor, but I would suspect that in theory, you could do the same thing by turning the flywheel. There is a trigger magnet around the center hole on the flywheel.

 

[kywings]

Re: 1998 force 75 hp Stator

1996-1998 75 hp only had one carb. There is a gasket between the intake and the carb. Not sure about adapter but will look. When you say "by-pass cover" are you talking transfer cover on the recirc drawings. I have 3. The middle one holds the fuel pump. Good Idea to check, I hadn't thought of that.

I like the terminal block idea. Any issues with water?

I'll give some thought to that trigger test. I saw a you tube video where the guy marked the fly wheel TDC for each cylinder then used a timing light to show each cylinder. His bad trigger showed it was firing two cylinders at the same time. Not sure if that is credible. Will be working on Friday and Saturday. I'll let you know what I find. Thanks for the help!

 

[pnwboat]

Re: 1998 force 75 hp Stator

Sorry about that, forgot that the 1998 75 HP only has one carb. This is the gasket/bolts that I'm talking about.

Gaskets 4 and 7 in the diag. below. The bolts that hold the adapter, item 1 in place.

Mercury, Mercruiser, Force, etc. - FUEL INTAKE SYSTEM - FORCE 75 H.P. (1998)

Idle speed mixture screw should be a minimum of 7/8 to 1 turn out from lightly seated. Usually in the neighborhood of 1 1/4 - 1 1/2 out. Every motor is a little different.

Might also do a compression check.

What spark plugs are you running?

Yes the By-Pass cover are the 3 almost square covers, of which one has the fuel pump mounted to it. You can usually see some evidence of fuel/oil leaking around the edge of the cover if the gasket is bad or not torqued down.

Haven't had any issues with the terminal block method in the 5 years since I modified mine, or any others that I've done. The older motors used terminal blocks for all the electrical/ignition system connections. Just use good quality components, not the cheap stuff made who knows where. Here's a picture of one that I did years ago (yellow box) with just a two position terminal block for the battery charging wires. Still looks the same as it did when I first put it on. No corrosion and no evidence of overheated wires.





Checking trigger while in the driveway with the motor on muffs using the timing light and marking the flywheel at TDC for each piston is another way to check the ignition spark. If it's firing when it's supposed to then the trigger should be OK.

 

[kywings]

Re: 1998 force 75 hp Stator

4&7 were replaced 12/2011. I'll recheck torque.

I performed a link and sync month ago. Idle screw is out 1 1/8 turns.

Compression is 120 all three.

L76V Champion. I have 2 year old QL76V's. Swapped back and forth no changes. Except $$

Very much like the terminal block. Looks better than the spaghetti mess I have. This is a must.

I tried that trigger test method while at my dock in the water. All three fire at TDC.

After all this I was down to trigger, stator or regulator. But now I'll be curious to check the torque on the intake or the by pass covers. Had not thought of those.

 

[kywings]

Re: 1998 force 75 hp Stator

Spent a little time on it tonight. I had to install the new recirc check valves. The valves I borrowed needed to be returned and I received the new ones. The new ones seal complete and the borrowed ones leaked a little. The checks inside my original fittings were missing all together. While I had the wire plate off I looked at the stator. Someone was nice enough to put a date on the wire harness. It was installed 9/2003. The windings are not sealed in red or black plastic and are exposed. So if it is a CDI stator its probably ok at 470 ohms. I think I need to pull it out of the water to R&R the barrel connectors and add the terminal block. I will check the torque on all intake bolts and for leaks on the by-pass covers before I pull it.

 

[kywings]

Re: 1998 force 75 hp Stator

pnwboat, On the CDI troubleshooting document it stated the ohm's should read 600-700. If that is true would mine be bad at 470 ohms?

 

[pnwboat]

Re: 1998 force 75 hp Stator

In the CDI Electronics 3 cylinder CDM ignition trouble-shooting guide page 86, it shows that the OEM stator reads 500 - 700 OHMs. CDI reads 500 - 600.
ISSUU - CDI Electronics Troubleshooting Guide - 2012 by CDI Electronics

In the CDI Electronics DVA charts, page 2 it shows the OEM stator 500 - 700 OHMs, CDI stator reads 400 - 600.

ISSUU - CDI Electronics DVA Chart by CDI Electronics

I would say that yours is close enough to either one that I would say it's probably good. You can verify by measuring the voltage with the DVA and your meter. Not saying that I'm an expert on the stators, but I've never seen a bad CDI stator. Not saying that they never fail. Have seen plenty of OEM stators go bad. But then again, there are probably a lot more motors out there with OEM stators, than CDI stators.

Just keep the stator readings in the back of your head. Check your gaskets and bolts first.

 

[kywings]

Re: 1998 force 75 hp Stator

Ok checked all the bolts I can get to and all were tight. The bottom and very top by-pass cover look ok. Cant get to all the bolts without removing the electrical plate. Would rather complete that while in my driveway. Looking to pull boat but pouring rain at the moment. Tomorrow for sure. The Carb plate looks good and bolts are tight.

I should get the DVA this week to check voltage. I read the doc's you listed on on your previous reply and they make sense. However on the Outboard Ignition.com site they list a 9amp and a 16 amp stator. The Mercury web site show the 16 amp for my serial number. The 9 ohms should be 400-600 and the 16 should be 600-700. All of these doc's are from CDI so I'm thinking mine is 16. (no expert just confused.) Do you have any experience with the two different amps? With all that I think the voltage test is in order. Ill let you know once I get the adapter.

http://www.outboardignition.com/support/174-2075K2.pdf
http://www.outboardignition.com/support/174-2075K1.pdf