Power trim causes power loss on OMC Cobra...?

[Stan's Customs]

After our first lake test run on this 1988 Four Winns, all shift linkage adjustments seem to work well..in fact better than I expected after the clunky shifting on muffs. Shifts very smooth really, which is good news.<br /><br />The carburetor has just been rebuilt and performs goog out of the hole, idles well etc....there is a problem though. At 3500 RPM or more the engine doesn't seem to make power like it should. It even popped back once or twice at full throttle, though only once or twice.. I think the carb is OK...thought that maybe the valve springs might be a little weak for full throttle RPM. I changed my mind about that when I noticed that the RPM's were affected when I trimmed the drive up and down. Loss of power if you will. Ignition interrupter malfunction maybe... I'm not sure. It doesn't seem like the trim could be related to much that could cause a power loss, any ideas?? Whatever it is I imagine it has something to do with the higher rpm fluctuation when over 3500 as well.<br /><br />If anyone has ever heard of this happening on a boat before I'd sure like to know what the cause was ...or any other suggestions as to what may be the problem area. <br /><br />Thanks...Stan

 

[Stan's Customs]

Re: Power trim causes power loss on OMC Cobra...?

"real goog" out of the hole as a matter of fact, more goog than usual..ha!

 

[arboatdr]

Re: Power trim causes power loss on OMC Cobra...?

You might want to look at your charging system. If your battery voltage isn't being maintained while running the engine can miss when operating the trim or a lot of accessories. I'd check the alternator and all connections first. Once you get this problem fixed you may find you have more than one. Keep us posted. DH

 

[tommays]

Re: Power trim causes power loss on OMC Cobra...?

the best thing you can do is hook up a meter to the battery and have someone watch it while you are doing the things that make the boat misfire <br /><br /><br />it is very common for a trim system to have a problem that drops the system voltage lower than nessary for good ingition<br /><br />the popping way be water in the fuel its very easy to see whats in your sepator and rule that in or out as a cause<br /><br />tommays

 

[Stan's Customs]

Re: Power trim causes power loss on OMC Cobra...?

Hmm...Ok I'll take a closer look. <br /><br />However all the gauges work properly...even the trim (imagine that). The alt. gauge shows between 13 and 14 volts when revved a little...and the battery is 2 weeks old. Since we had been working on the boat and using the trim, ignition, and so on without running it much ...I put a good charge on it the day before we took it out, to make sure I didn't get towed in..<br /><br />Wouldn't the battery carry the load for a little while by itself even if the alternator was defective? The dash gauge says it's OK..but they lie sometimes...<br /><br />Good thought on the fuel condition too...however the carb was where we started on this project ..it appeared to have had moisture when it was disassembled for cleaning. So I pulled the floor pannel removed the gas gauge sending unit and pumped the tank almost bone dry, with an old electric fuel pump I've got screwed to a board... before running the new rebuilt carb. Then after installing a new filter/separator added 12 gallons of fresh fuel with the proper amount of stabilizer for the winter.<br /><br />I've been puzzling what this thing acts like so as to better describe the symptoms...it finally came to me. It's kinda like it bumping a rev limiter on a hot rod..except at much lower RPM than I normally would carry a smallblock to. These things don't have a rev limiter built into the system do they?? It does it at higher rpm's without the trim operation, it's just more noticeable when the trim is activated...I think ?<br /><br />Odd acting to symptom say the least...thats why I keep looking at an intermittent fire situation.. I guess it could even be a weird acting coil fixing to go out...?<br /><br />Stan

 

[louc]

Re: Power trim causes power loss on OMC Cobra...?

2 things:<br />I have heard of the trim causing that to happen, there was a service bulletin on it I think, do a search on the forum you may find it. I seem to remember it had something to do with the resistance wire in the harness.<br />On my 88 200 Horizon with the 4.3 Cobra, I had a lack of power problem that my mechanic traced to a bad antisiphon valve on the gas tank, they can get corrosion in them and the ball valve sticks and does not allow enough flow to the fuel pump.<br />I assume you have also checked the water seperating filter and the carb filter as well?<br />The shift interrupt should not be engaging when it is in gear, that would cause it to run REALLY bad, like it lost 1/2 of the power.<br />I'd also go back and check all of the batt cables, connections, etc. Glad to hear yours shifts well. Just make sure when you change the gear oil you do it according to the book!!

 

[Rickfifty]

Re: Power trim causes power loss on OMC Cobra...?

I've got an '88 OMC Cobra 4.3 that does something very similar. In the upper RPM range, as soon as I hit the trim button the boat jerks hard from loss of power/rpm's. Let off button and it's OK. I've asked around a bit and more than a few people said to check and clean the ground on the back of the motor near the starter. Mine has a stack of ground wires on a long stud. Apparently it gets corroded easily. I've done the cleaning but have not tested the results. May be something to look at as it sounds similar to my problem.

 

[Rickfifty]

Re: Power trim causes power loss on OMC Cobra...?

I've got an '88 OMC Cobra 4.3 that does something very similar. In the upper RPM range, as soon as I hit the trim button the boat jerks hard from loss of power/rpm's. Let off button and it's OK. I've asked around a bit and more than a few people said to check and clean the ground on the back of the motor near the starter. Mine has a stack of ground wires on a long stud. Apparently it gets corroded easily. I've done the cleaning but have not tested the results. May be something to look at as it sounds similar to my problem.

 

[Lou C]

Re: Power trim causes power loss on OMC Cobra...?

interesting--I don't recall having the problem before changing my batt cables, this spring I changed them because the original ones were corroded and I was putting in a dual battery system. I did clean off both ground studs which are on the rear of the block, bellhousing area. Not that easy to get too but reachable. I then coated the nuts and exposed terminal with OMC triple guard grease, which pretty much prevents corrosion even in a salt water area. This year I ran the boat a lot at high speeds and never had a problem with it cutting out when trimming. BTW the trim pump draws a TON of current, watch the volt meter when you trim!

 

[Stan's Customs]

Re: Power trim causes power loss on OMC Cobra...?

Yea Haw.. <br /><br />I believe that I have found part of the problem... !!<br /><br /> The distributor has a pointless aftermarket ignition by Pertronicx. According to the Tech guys at Pertronics the distributor plate in this one was mounted in the wrong position. I have remedied that problem according to a fax diagram they sent me. ...unfortunately when removing the rotor and magnet asssembly it came apart when pulling it off. I've had to order the magnet ring for the rotor....so it'll be a few days before I know if that part is fixed for sure.<br /><br />The losss of power when the using the trim is a separate problem that amplifies the already existing power loss at higher RPM....I think ? <br /><br />Sooo...looks like the power draw from the trim is an issue still to be dealt with. Whether it be the fused connection, a poor ground or too much draw for the alternator. From these post it seems like any of the above would not be too uncommon.<br /><br /> The guys at Pertronix seem confident that the power loss at higher rpm (when not activating the trim) is most likely caused by the position of the module plate in the distributor, and that it probably would not manifest itself until higher RPM's, sinceit is an rpm sensitive mounting plate position. Therefore it would run smooth on the lower RPM ranges and accelerate to a point, properly. Kinda like the rev limiter situation I was describing earlier. <br />If this is correct it would explain the odd acting symptoms...just didn't make much sense. Hope I'm on the right track now.<br /><br /><br />Thanks every one...if there are any other ideas on the trim activated loss of power, please lets hear 'em. It ain't fixed yet! Just have a direction to go...<br /><br />Stan...

 

[affa]

Re: Power trim causes power loss on OMC Cobra...?

Hi<br />The delco EST ignition has a filter in the positive lead to the coil, this is because the voltage drop when youre using the trim, and this filter will help so its not misfiring.<br />Check the voltage at the coil when youre trimming, and see if it drops to much.<br />Regards<br />Affa

 

[Stan's Customs]

Re: Power trim causes power loss on OMC Cobra...?

10-4 Affa...<br /><br />I'll do that. What is the expected voltage drop without misfiring...I'd guess 10 volts or more is necessary ...strickly a gues. Don't really have a clue.<br /><br />Thanks Stan

 

[tommays]

Re: Power trim causes power loss on OMC Cobra...?

stan<br />the meter is more about seeing what the trim system is doing<br /> the blip in the engine is the end result not the problem as the trim motor ages and brushes and other parts wear it will draw more current than it should and will get worse over time if not repiared when it was new it did not blip the motor<br /><br />tommays

 

[seahorse5]

Re: Power trim causes power loss on OMC Cobra...?

The service bulletin that came out about the 4.3 misfire with the trim activated suggested different plugs, a heavy duty hi-output coil, better points, and, if needed, the shortening of the resistance wire to the coil. <br /><br />Also battery size and condition makes a difference as well as the battery and trim cable connections. Remove each one and sand them and the mountings until they shine. Adding a ground wire #10 from the alternator frame to the engine block sometimes helps.

 

[seahorse5]

Re: Power trim causes power loss on OMC Cobra...?

Check with any Johnson Evinrude dealer that handled the OMC Cobra Drives. There are some dealers that were Cobra Drive only, also. Knowledgable independent shops may have a copy of the bulletin that you need.

 

[Rickfifty]

Re: Power trim causes power loss on OMC Cobra...?

Anybody(seahorse?) know where to get a copy of that service bulletin?

 

[Stan's Customs]

Re: Power trim causes power loss on OMC Cobra...?

WEll... <br /> the distributor part came in and after the rain let up I was able to put the boat on the lake. The wrongly positioned ignitor plate was most of the problem. The engine goes to 4600 easily with me only in the boat. It would probably go higher trimmed out further, but that's about it for the cam, judging from the increase in rpm without increase in power. I figure that a loaded boat will keep me at max rpm @ wot and full trim. I really thought this boat would be way under proped with this 17, but it seems good. It's a Four Winns 200 with a 5.7 Cobra. Most of my similar boats in the past used a 19 to ski..sometimes a 21, never a 17.<br /><br />Now back to the other problem...When the trim is "bumped" the motor cuts out a little. But when the trim is firmly held in it does "not" cut out??<br /><br />I generally just bump the trim till it sounds good, so this is really awkward. When you nail the switch it doesn't cut out just goes to far. When you just bump it it cuts out a little and you can't tell if it sounds just right ..if you get my meaning. (right before cavitation).<br /><br />Seems like it would be worse the longer you hold the trim button in ...but no. Does that still act like the trim motor is pulling too many amps or some similar problem? Could it be the control handle switch someway?<br /><br /><br />Thanks ...Stan

 

[Stan's Customs]

Re: Power trim causes power loss on OMC Cobra...?

WEll... <br /> the distributor part came in and after the rain let up I was able to put the boat on the lake. The wrongly positioned ignitor plate was most of the problem. The engine goes to 4600 easily with me only in the boat. It would probably go higher trimmed out further, but that's about it for the cam, judging from the increase in rpm without increase in power. I figure that a loaded boat will keep me at max rpm @ wot and full trim. I really thought this boat would be way under proped with this 17, but it seems good. It's a Four Winns 200 with a 5.7 Cobra. Most of my similar boats in the past used a 19 to ski..sometimes a 21, never a 17.<br /><br />Now back to the other problem...When the trim is "bumped" the motor cuts out a little. But when the trim is firmly held in it does "not" cut out??<br /><br />I generally just bump the trim till it sounds good, so this is really awkward. When you nail the switch it doesn't cut out just goes to far. When you just bump it it cuts out a little and you can't tell if it sounds just right ..if you get my meaning. (right before cavitation).<br /><br />Seems like it would be worse the longer you hold the trim button in ...but no. Does that still act like the trim motor is pulling too many amps or some similar problem? Could it be the control handle switch someway?<br /><br /><br />Thanks ...Stan

 

[tommays]

Re: Power trim causes power loss on OMC Cobra...?

stan<br /><br />with out hooking up a meter to the battery to see how the system is being effected by use of the trim your shooting in the dark <br /><br />give it a try your going to have to use a meter to repiar what ever is the final cause if your not the orginal owner who can say what someone may have done to the wireing in the past<br /><br />tommays

 

[Stan's Customs]

Re: Power trim causes power loss on OMC Cobra...?

WEll... <br /> the distributor part came in and after the rain let up I was able to put the boat on the lake. The wrongly positioned ignitor plate was most of the problem. The engine goes to 4600 easily with me only in the boat. It would probably go higher trimmed out further, but that's about it for the cam, judging from the increase in rpm without increase in power. I figure that a loaded boat will keep me at max rpm @ wot and full trim. I really thought this boat would be way under proped with this 17, but it seems good. It's a Four Winns 200 with a 5.7 Cobra. Most of my similar boats in the past used a 19 to ski..sometimes a 21, never a 17.<br /><br />Now back to the other problem...When the trim is "bumped" the motor cuts out a little. But when the trim is firmly held in it does "not" cut out??<br /><br />I generally just bump the trim till it sounds good, so this is really awkward. When you nail the switch it doesn't cut out just goes to far. When you just bump it it cuts out a little and you can't tell if it sounds just right ..if you get my meaning. (right before cavitation).<br /><br />Seems like it would be worse the longer you hold the trim button in ...but no. Does that still act like the trim motor is pulling too many amps or some similar problem? Could it be the control handle switch someway?<br /><br /><br />Thanks ...Stan