85 Mariner 50 mechanical problems

[bassfish12]

I've got a 50 mariner on a 14 ft procraft. Has ran fine over the years however last time out It dropped down from 30 mph to about 8 mph after running for 15 mins. since then it won't run any faster. Out of water it runs fine. I had a guy check compression and all cylinders were good. He also cleaned the carbs and I changed out the fuel lines and bulb. Plugs are also in good shape. Took it back out today and the same thing is still happening. It gets up to 15 after initial take off then immediate hesitation and back down to 8 mph again. never gets out of the lower gear. It did do this one other time in the past but after cutting the engine off and fishing for a bit, it ran fine next start up. I was wondering if it could be a powerpack problem or stator issue. Any ideas are appreciated.

[EuropeanAM]

A good starting point would be to check SPARK when the engine is acting up.

[bassfish12]

Thanks, as you can probably tell I'm not a mechanic but this boat problem has persisted for 8 months and 2 visits to a shade tree mechanic. My friend's boat did a similar thing and he needed one of the power packs replaced. I'm assuming and i use that word loosely that spark had been checked along with compression as more obvious choices on my initial first visit. He's also the same guy that replaced the power pack on my friends boat. He seemed to think the power pack was OK on mine even when I took it back the second time and he made some timing adjustments. Just a little frustrating when it runs great in the driveway, no loss of power or hesitation but then won't run in the water once load is placed on it.

[EuropeanAM]

Switch box (that's what you're referring to as a "Power Pack") is a possibility, as are coils, plug wires, spark plugs, TRIGGER, or the stator.

Triggers on this model are beginning to experience the "green wire disease"... and sometimes will function one moment, and NOT function at others (wires internally break in the trigger harness, making a connection at one time, but not at another).

Remember that the trigger MOVES with the throttle linkage... so it's harness does plenty of "flexing".

[bassfish12]

At this point I've searched around and found the Mercury/Mariner reistance charts for stator, trigger, and ignition coils. I tested using the ohm parameters since I don't have a DVA tester. On the stator, the low side blue to blue/white tested infinity while the red to red white tested within parameters. The trigger also tested within parameters listed. I also bench tested the rectifier which also failed. Is it safe to say that resistance testing on these parts is reliable enough to prove they need to be replaced, regarding the stator and the rectifier. At this point I haven't been able to remove the flywheel and visually inspect the trigger and stator (still waiting on the flywheel removal tool). Generally do the stator and trigger both need replacing or is it possible for the trigger to be Ok.

[luvdmymerc]

Hey bassfish12.....Something else you might check it the throttle linkage. The only reason I'm chiming in here is that I just fixed a buddy's boat that was acting very much like yours. It turned out the throttle actuator and actuator plate were both damaged and not engaging the carburetors like they are supposed to when pushed past a certain point. The parts are plastic and had just split allowing the throttle cable to push past them rather than opening up the carburetors. Worth a shot.

[bassfish12]

I'll take a look at it and get back to ya on it.

[bassfish12]

No problems with the linkage.

[EuropeanAM]

Replace ANY components that repeatably fail the resistance tests.

When testing the trigger- be sure to move the THROTTLE from idle to WOT and back to idle a couple of times, while monitoring the resistance readings. If readings fluctuate in any substantial fashion- REPLACE the trigger (it's harness is likely failing).

[bassfish12]

Now I'm really confused took it out with the stator wires off of the rectifier to see if it made any difference. Same as usual begins to plane out at bout 20 mph then drops back down to 8mph. This time I decided to squeeze the primer bulb with the engine control at WOT but only running at 8 mph. The primer bulb was inflated but I decided to squeeze it and see what happens. The boat picked up speed for a few seconds back up to 16 to 18 mph and then died down immediately to 8 mph. I turned the engine off and waited for the bulb to reinflate. I took off again and back up to 20 and immediately back down to 6-8 mph again I squeezed the bulb again and it increased speed and then back to idle within 3-4 seconds. Now it only did this 2 times after that whenever I squeezed the bulb no change in speed. I tried to repeat this at least 7 to eight more times. So now I'm confused is this a fuel pressure issue or a carb issue. Is it possible to have fuel pressure issues and ignition issues together. I was pretty sure it was a stator/ trigger/rectifier issue intil squeezing the bulb made it increase speed. Why did this only work twice and not every time I tried it. So any ideas on what to do now. i've already changed the plugs and have good spark to all cylinders . I'm using a brand new gas can with brand new bulb and lines already. I've also replaced the fuel filter as well. Do i need to rebuild the carbs. I'm not sure where to go with this now.

[EuropeanAM]

You very likely DO have more than one problem.

Start with the known electrical problems.

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by EuropeanAM &raquo;</td></tr><tr><td class="quote">Replace ANY components that repeatably fail the resistance tests.

</td></tr></table>

Once that problem has been addressed, deal IMMEDIATELY with the fuel delivery problem. I would recommend going through the carbs (complete disassembly, rebuild them, and reassemble)... then perform a complete Sync-N-Link proceedure (outlined in the Engine Synchronization and Adjustments section of the OEM Service Manual).

Also recommend going through the fuel pump... and addressing ALL items found in the following post:

http://www.bbcboards.net/zerot...first

[bassfish12]

Will do and thanks for the link about the primer bulbs. May be a little while before I can get to some of this though unfortunately. Will update progress as I can.

[bassfish12]

So it's been a while but I figured that I'd give an update and look for some advice. I decided to rebuild the carbs and the diaphramatic fuel pumps first. This was the less expensive of the issues considering the costs of the stator and trigger components. I also put in new floats along with gaskets for the fuel pumps and float bowls. I understand that there could be ignition issues but I figured start with the less expensive first. When I first cranked it up in my drive way it fired up and was reving really high in idle (i don't have a working tach but it was over 3000 RPMs I'm sure). So i immediately shut it off. After a few starts, and adjustments to the carb idle screws no change. I finally had to make significant adjustments to the throttle cable and idle stop screw to get the RPM's down, which worked. However, now it's hard to start and then when I try to put it in idle it continues to stall out. I tried countless numbers of times to adjust the idle mixture screws with no success and no change in rpm while it was running. I also tried to make small adjustments to the idle stop. The only way it would stay running was for the idle to be up way too high for normal. More than 2000 RPM or if i gave it gas. My goal was to get it running to try it out again and see if it fixed the problem. If not go on to the ignition issues and replace the stator and trigger. I don't won't to spend an extra 300$ to 400$ on unnecessary parts. Now i can't get it to stay running at a low enough RPM to put in and out of gear. Does this sound like a carb issue. Should I take them back off and replace the new floats with the old ones. The new floats did not have adjustable tabs since they were made of plastic but did match up right on with the old float level when installed. Would this even have anything to do with it not running? Also all gas lines and fittings are new and no leaks detected. It was at least running and idling before I rebuilt the carbs so why the significant change in idle with the rep

[EuropeanAM]

Did you perform a COMPLETE Sync-n-Link proceedure (as outlined in the Engine Syncronization and Linkage Adjustment section of the repair manual) AFTER carbs were reinstalled?

This proceedure is MANDATORY, as removal of the carbs alters their position, and results in incorrectly synchronized throttle plates and linkages.

[bassfish12]

Wasn't able to do the sync and link procedure since i couldn't keep it running. The first step in my manual is to crank it put in drive and adjust the primary pick up at 7 to 8 degrees BTDC if i'm remember correctly. I couldn't keep it running long enough to perform the timing and adjust it. Wouldn't the rpms have to be down to be able to do this procedure and then move on to adjusting the secondary pickup and timing at 5000 rpms. I know the timing needs to be performed but I didn't think it could be done without getting the rpms down first. Is this correct? In addition the multimeter I was using to look at rpms was not working correctly and my boat does not have a tachometer. Do you think the new floats could be affecting the idling. Should i put the old floats back in they didn't look that bad, just thought I'd replace them since I had the bowls off anyways.

[EuropeanAM]

Might want to read back through that section of the manual.

You need to perform the throttle pickup timing at CRANKING SPEED (300 RPM). That means no fuel in carbs, all plugs except #1 removed, timing light on #1 plug wire.

[bassfish12]

Good point will do. Thanks for the advice. I"ll have to find that in the manual it wasn't in the same section I was looking at for tuning. It went straight to adjusting the idle screw, cranking and adjusting the timing while running at 8 degrees. I don't know why adjusting at cranking speed wasn't in that section first. It's a clymers shop manual.

[EuropeanAM]

It's a clymers shop manual.

Hmmmnnn... that might just be the problem.

[bassfish12]

Well it ended up being the intake gasket. I accidently put it on upside down, therefore the boat was running on only one carb. After someone else discovered this the boat is back to running normally. Took it out this weekend and all the power is back. I guess it was probably the fuel pump on one of the carbs that was causing the original problem. Thanks for the help.