Service bulletin details please

[gtoboy]

I have this same problem on 5.7l omc.Would you have the service bulletin number or details for the comments made by Clanton below please?<br /><br />RPM drops when I Adjust trim or tilt <br /> <br />forgetaboutit When i'm at WOT and adjust trim or tilt the Rpm drops why?. Thank for any help i can get 2002-05-31<br /> <br />dms I believe it's because you're essentially changing the "pitch" on your prop. The same reason your rpm lowers when you go to a higher pitch prop. 2002-05-31<br /> <br />Boatist forgetaboutit<br />It is normal for rpm to change any time you trim boat. When you trim the motor in the bow will go down. That means more wetted surface, slower speeds and lower rpm. When you trim out the bow will go up, less wetted and higher rpms until get out far enough that prop angle is not at 90 degree to water then again speed will drop and again and rpm will go down. If trim out too far rpm will go way up and boat speed will drop as prop cavitates. 2002-06-01<br /> <br />Boatist forgetaboutit<br />It is normal for rpm to change any time you trim boat. When you trim the motor in the bow will go down. That means more wetted surface, slower speeds and lower rpm. When you trim out the bow will go up, less wetted and higher rpms until get out far enough that prop angle is not at 90 degree to water then again speed will drop and again and rpm will go down. If trim out too far rpm will go way up and boat speed will drop as prop cavitates. 2002-06-01<br /> <br />nnosker Thats what makes it more fun, the less you see the faster you go. The more you see, gives you more time to enjoy the scenery. 2002-06-01<br /> <br />clanton when you are on plane trimed and running smooth, if you engage trin up for a second and the rpms drop 2/400 rpms, check stator output to powerpack. Engine may run rough for a few seconds.<br />There is old OMC service bulliten about this for 35 amp stators.<br /><br />Edited 6:30<br />Other post said engine surging. Time for compression check. Check magnets in flywheel, ignition systen check, Fuel pressure and vacumn. 2

 

[clanton]

Re: Service bulletin details please

My post was for Evinrude/Johnson outboards engines with 35 amp stators. But when you use trim, it draws a lot of juice. If you just touch the trim up, after on plane and at the correct trim, and rpms drop, its because the trim is drawing power away from the ignition system, which is common on the OMC outboards with 35 amp system. I dont how this happens, because the ignition and charging is not connected, only use the same magnets in the flywheel. If this is happen on your 5.7, if you connect meter to supply voltage to dist, you should see the voltage drop.

 

[gtoboy]

Re: Service bulletin details please

RPMs drop but only at high speed. So I try to trim the motor to get more speed and rpm's drop basically taking me out of plane. I agree that it may be pulling juice fromt he distributor but why not at idle or lower speed?

 

[gtoboy]

Re: Service bulletin details please

actually it happens even when i use the trim tab system. What could cause this?bad coil?

 

[clanton]

Re: Service bulletin details please

I would look for the power supply for the trim systems, they may have been moved from the orignal loctation, and spliced in where they dont belong. Alternater output may be low. Some systems had wire from alt to dist, which powered the dist when running, if alt output not correct, it effects the dist.

 

[gtoboy]

Re: Service bulletin details please

Thanks for all your help. I tested the voltage at the coil. it was 1o volts at idle went up to 11 when rev'd up and drops even lower when I use the trim. getting good voltage out of the alternator. I will check the wiring harness. Again Thks so much.

 

[Boatin Bob]

Re: Service bulletin details please

This problem seems to happen quite a bit and most of the time it seems to be a loose or corroded connection. I would check, clean and tighten the battery conections but also at the solenoid that the battery cable goes to, it feeds everything else from that single point, your battery should be feeding those hydraulic motors...maybe it's not getting fully charged?

 

[deckhand]

Re: Service bulletin details please

There is a service bull. out on this problem. If I remember correctly (I will ck) the alternator is not getting good ground from mounting bolts fix was add external ground wire to alt.

 

[P.V.]

Re: Service bulletin details please

The bulletin referenced by Oldhand was for 3.0 litre Cobras. OMC did have a bulletin that pertains to gtboys problem. The problem was more commen to the V-6 engines but will relate to the 350ci also. The latest OMC breaker points and condensor is different than the orginal. OMC had a high output ignition coil, again, different from the orginal and also, shortening the resistor wire in the wiring harness. If I remember correctly, and I could be slightly incorrect, you shorten the wire by removing 22". This lowers the resitance of the wire and provides additional voltage to the coil. Hense, when you activate the trim (and draw amps from the system), there's still available voltage for the ignition. There's actually two bulletins so go ask a BOMB dealer to show them to you. The bulletins tall you the specifics, so don't go by my vague memory!!!