low power 90 merc

[Hop]

low power 90 merc

Ok fellas, first question.  90 merc (97) has been fine. Today started out ok then bogged down, couldn`t get over 8 mph.  Going to try external fuel tank  and uel line.  Since it`s oll injection, is it ok to use fuel tanl w now oil in tank?  IF That doesn`t work `m guessi g fuel pump.  Is that changeable by a guy that usua;;ly changes plugs and filter?  Any ideas appreciated.  Hop

[shawn393]

my guess would be one of the ignition coils went bad

[guffins fisherman]

I had a Johnson 115 that would do that, then run fine, bog down, run fine. Turns out the new coils I had put on weren't plugged in tightly, and were only making a solid connection intermittently. Arcing bad. My bet your Merc is doing the same thing, or a coil just went bad altogether.

Sent from my XT1585 using Lake Ontario United mobile app

[Hop]

Thanks, I will check them.  Is the plug wire that goes to the coil supposed to actually make contact with the top of the plug? 

[Xxx]

1 hour ago, Hop said:

Thanks, I will check them.  Is the plug wire that goes to the coil supposed to actually make contact with the top of the plug? 

 

Well yea!! Push the spark plug ends down if their not all the on already, if not you can hear or feel a slight pop. Then the plug wire is on correctly

[Hop]

Yea, my bad.  I meant the end of the wire that goes to the coil.  It was 2 am when I wrote that!

[Beanstir]

I have been following this as I had similar problems. Full throttle then bogs down to 15 mph. Then it was full throttle to 8 mph.  Last fall I replaced the trigger assembly, there was a wire that was rotten the whole length. After installing this part it still was not working. This spring I could not get it past 8 mph. I had a marine mechanic diagnosed my engine using a cylinder leak down test. All 3 cylinders at 25 - 30%. He said the engine was done. I got a second opinion. All 3 cylinders had good compression. Replaced 3 reed sets, middle cylinder was not firing properly. replaced CDI box. Put it in the water and used fresh gas, I had old gas from last year in on-board tank. Adjusted Lever Spark Advance. Adjusted idle needle. We took it out today in real rough water for a test run. We had a great sounding and working engine at full throttle for a moment but with the rough water we could not test for long. I am going to get rid of the old gas and when the water gets calm take it for a long run. I am crossing my fingers that this fix will last long term. Beanstir

[Hop]

Thank you for your experience.  I have pulled the fuel pump and am having that rebuilt.  Will see how that does.  For a non mechnics benefit, what is a cdi box and what does it do.  Is it easily accessable on motor and easily replaced?  Thanks again.  I am starting t panic cause the Seneca Lake Derby is next week!

[Sk8man]

With your usual luck you wouldn't even need your boat  and probably catch the winner right off your dock while sipping a cool one with Jeri  Good luck with it bud You can ride with us if things go south...

[Xxx]

1 hour ago, Hop said:

Thank you for your experience.  I have pulled the fuel pump and am having that rebuilt.  Will see how that does.  For a non mechnics benefit, what is a cdi box and what does it do.  Is it easily accessable on motor and easily replaced?  Thanks again.  I am starting t panic cause the Seneca Lake Derby is next week!

 

CDI - captive discharge ignition, basically it the brain of the cylinders that the plug are attached to. It tells the cylinder when to fire and the amount of electric, like it's your timing advance also, the reason they use more than 1 is not to charge the customers, more but to leave at least 2 or more cylinders working, so your not stranded, even on the smaller 2 stroke kickers have 2 coils for this reason. This is my luck with electrical parts!! I had a Evinrude V4 88spl and a force 15hp kicker left the dock with 6 cylinders working was out in front of Stoney Isl. winds started to pick up and we lost a cylinder on the kicker. So we decided to call it a day. Started the main got up on plane but couldn't keep it on plane, WTF switched the bilge pump on felt like we were heavy!! No water came out. Long story short we lost 2 cylinders on main and 1 on the kicker, in order to have enough power to get behind the break wall at Henderson we needed 3 cylinder 2 on the main 1 on the kicker, we risked going through the cut underpowered as it narrow and you need to be on your game, we made it. It's a hole differant world in the bay. Two hrs later we were at the dock. My dad at the time was in his 70's he was scared, he put his life vest on before the cut already. He congrats me on my skills he thought we'd never make it through the cut, if your not strait at the cut to fit through the hole your up shyts creek. We got a new CDI box at a big marinia up by the TI bridge on the rt 6 side, got back put the new box on and we were back in buisness. There easy to install just mark your wires on the old box so you have something to copy off of. Best of luck HOP, with your pump and hopefully that's your cure!!! PAP

[HB2]

How old is the fuel line ? mine did same thing and fuel line had inner sheath and colapsed inside. Changed line and ran great. Ethenol fuel . 

Edited May 21, 2017 by HB2

[Hop]

HB2, I tried an external tank w/dierent fuel line, same results.  Pap, are you saying there are 3 cdi?  Not sure what you met.  For the fellow with the 70 hp problem, I inherited a 1990 fuel injected from my dad, ran great, then started doing what you described.  Took to dealer, put new "power pack in ran and still runs great.  My kids abuse the heck out of that motor and it just keeps going.  Les, thanks for the offer, but wouldn't that be aiding and abeting the enemy??!   I pulled Dads egg sinkers, hooks, and needles out,e to I`ll drift w/sawbellies.  I think most guys have gone into "stealth" modr this week.  Have noticed something pretty interesting the last 3 weeks, will e-mail you.

[Sk8man]

"but wouldn't that be aiding and abeting the enemy??!"   Good one bud.  I planted a listening device in the chair when I last visited you....you might be history now Problem was all I could hear on the tape was Jeri sayng" Are you sure that would work?

Edited May 21, 2017 by Sk8man

[Xxx]

2 hours ago, Hop said:

Pap, are you saying there are 3 cdi?  Not sure what you met.  

 

Didn't you ask what a CDI box is and what it did? Captive discharge ignition, they are the brain of depending on how many cylinders the motor has say 4 usually they are paired up to at least two cylinders. They control the spark, and the timing of the spark, usually it's an easy tell because one plug will be wet and black, and if you switch the plugs around that same "cylinders" plug will be wet and the one you switched out is now working, sorry for the confusion. Kinda like the newer cars instead of having a distributer, now each cylinder has its own coil pack, and a computer telling it when to fire, the CDI is the early style computer box that controls the cylinders that the spark plug wires go to say a V4 one CDI box would control 1-3cyl and the other would control 2-4 cyl--: just an example. Power pack/CDI same difference.

Edited May 21, 2017 by pap

[Hop]

OK,  must just have one, being a 3 cyl 90 hp.  Tks.

 

 

Ok Les, let the ball busting begin...

[shawn393]

no you have 3.every cyl has it's own

[Hop]

HB2, you called it  Changed diaphragm in fuel pump, no change.  Talked w/ F. Barrett from .Barrett Marine, he insisted it was a fuel restriction problem.  So, I installed new fuel line and fuel filter.The fuel line had indeed delaminated inside and in fact a small piece got up into filter.  Motor runs like new now.  I failed to follow the K.I.S.S. rule.  (Keep it simple, stupid)  Thanks to all who replied with suggestions.

[Xxx]

Well I'm glad you found it, I'm not that informed with the reed type carb's. I do remember my buddies pizzing & moaning about reeds with their snowmobiles, I can't believe it's going to be more expensive then the cbi boxes. Great job on the diagnostic testing!!