'92 70hp problems ... the continuing saga!!

[Mr. Ed]

I hope that's what the problem is. Took the boat out yesterday and the results were similar to Fri ... a very slight hesitation and no bogging. Had my Bro-in-law out with me, and he kept asking me 'so what's the problem with the motor?' The hesitation was so slight, he could not detect it. The only thing different now vs last week is that I pulled the CDI to test the Ohms on the bench ... then I obviously replaced it later.

I should be seing some parts my way Mon or Tues. So I'll be able to mess around with it on Wed, I'll keep you all informed.

[Mr. Ed]

Just an update ... Finally had a chance to stick the new CDI in and drop it in the lake. Well ... looks like the CDI was NOT the problem. Took it out yesterday (with new CDI) and it bogged as bad as ever. Funny thing is the weekend before last, I could not hardly get it to bog down. I still do not like the feal of the potentiometer (sp?) on the CDI for the timing ... the old one feals rough when you move it.

So, back to fuel issues I guess .... like Hamfisted thought all along. I have both jets and new floats ordered for all 3 carbs. Along with new gaskets for the prime start system. Ordered 12 days ago ... hoping they get here soon (ordered from this sight).

Anymore thoughts out there?

Ed

[jb123]

have you watched your carbs during operation/which spray and which dont ? watch them at idle and mid range. have you sprayed gas with spray bottle to listen to the change or choked each throat with your finger at a higher idle? pulled each plug wire to isolate the missing cylinder? the smallest particle will load up your carbs. i would also suggest the new yamaha 10 micron spin on filter to help from further clogs.

[Mr. Ed]

jb123 - all carbs look to be operating the same, as far as gas spraying. I have pulled plug wires, and choked off the carb throats ... But have not tried the spray bottle. Will put it on the list. Sounds like my carb parts will be here tomorrow, so I will pull them tonight and get them soaking, in case I did pick up some crud.

I will have to get my wife out this weekend and have her drive ... while I hang over the motor. PArt of my problem is that is a somewhat intermittent issue. When I have had another adult on board (not usually the case) the motor would not bogg down, which makes it tough to troubleshoot.

Thanks,
Ed

[drmarke]

I read the postings mostly for interest and learning! Are all plugs new and /or look the same? Could there be a cracked plug or bad plug wire causing the intermittant problem? Did you check the dynamic peak voltage output at the coils while boat being cranked (rather than the ohms test)?
Just my thoughts for what they are worth.
Mark

[drmarke]

The dynamic peak voltage output test was something that was recommended on my Mercury engine (for intermittant running problems after fuel issues have been addressed). I just reveiwed my Yamaha Shop Manuel and saw NO such test suggested or normal values given. Of note I did read the the Ohms readings could be off if the engine is tested "hot" rather than cold and if a different Ohmmeter is used that the specified Yamaha meter due to internal properties of the meter itself.
Mark

[Wally]

Ed, have you tried kicking that motor or threatening it with a sledge hammer?

Seriously though, you need to check whatever you haven't checked yet. Replace the spark plugs and make sure the connectors are tight. You might have an internal crack in one.

When you take the carbs off check the reeds inside the cylinder openings and make sure none look cracked or broken. And, make sure all the gaskets/Orings are seating properly on the carbs. I had to rub a little grease on mine to make them stay put while putting the parts back together.

Replace the squeeze bulb. It could have a bad valve which becomes an obstruction sometimes.

Check for any possible air-flow obstructions.

Check the oil injection system to make sure it isn't over oiling when opening the throttle.

Hopefully one of those will solve the problem.

Wally

[Mr. Ed]

Well ... you got me on the peak voltage ... I don't know about that. I'll have to check my shop manual as I did not see anything about the 'special' Ohmmeter (maybe it is for newer models?). My ohm tests were ran cold.

As far as the plugs ... they are new, and with the little bit of running I've done, all look good and the same from cylinder to cylinder.

I think part of the key here is that it will ALLWAYS start right up (even if it stalls out). It will only bog down after the boat is moving about 5mph (on the GPS). My tach has always been squirrelly so I don't know the rmp that it begins to bog down ... but it is pretty much the same mph all the time.

[Bazooka Joe]

That is very interesting that it bogs at a consistent boat speed. This sort of indicates a problem associated with a vibration frequency within the boat & motor.

Have you investigated the insides of the control box? Perhaps corroded connections or a nearly broken wire or a shorting of the keyswitch? Maybe something with the emergency kill switch?

I'm not sure offhand if the Yam system grounds the ignition from the control box or supplies current to the ignition system. Maybe disconnect some of the control wiring?

[jb123]

also, run it at night to see if theres any errant arcing.

[Bazooka Joe]

Describe the bogging a bit better. Is it losing all the cylinders or maybe just one? Dying bog w/ engine firing, or dying like somebody hit the kill button? Or, a "baaauuuuuuuuhhhh" continuous bog, or a "baaauuhh-h-h-h-h.. thug" dying engine bog?

Here's something I thought of related to a specific frequency vibration- With snowmobiles, if the carb needle & seat get worn, there can be possibly similar problems as I think you are describing. What happens, is that the engine will idle just fine, but at certain rpms, the needles hit the critical frequency and will vibrate and allow fuel to gush into the carbs, creating a rich jetting condition. You can trouble shoot this by unhooking the fuel line and take a short run on just the gas in the carbs.

[Mr. Ed]

Wally - Plugs were replaced during all this, and none are discolored. I have used 2 diff fuel lines (the one for the motor and the one for my kicker/aux tank) ... and I replaced the line & bulb on the boat anyway. Oil injector is new (last winter) and the motor was running fine after replacement. Will double check the reed valves (carbs are off now, waiting for the above mentioned parts) tonight, but did not notice anything before and no blow-back through carbs.

Bazooka - Interesting thought! If I remember correctly, it will bog down just opening the throttle plates as well. However, I've tried so many things ... I can't be for sure, will have to try again. As far as describing the bogging ... easier said than done, LOL. But I'd have to go with your, baaauuuuuuuuhhhh. I believe it is all cylinders, as it is very even, no coughing, chugging, etc. And you don't see the typical vibration of loosing one cylinder. This is why I had it stuck in my mind ... timing/CDI box. As far as the frequency vibration thing .... I think you are talking float needle and seat?? These were replaced when I did the preventive carb rebuild over winter. Again, the motor ran fine several trips out after the rebuild. But will try your suggestion if/when I have troubles after the new jets and floats are installed.

jb123 - Excellent, and simple, idea I should have thought of!! Will try after sticking the carbs back on.

Until then ... I'm sitting here waiting for the brown truck to arrive.


Thanks guys,
Ed

[Mamaguevo]

Hi Ed, I've being thinking about your problem seriously, and my recommendation are:
1.- BURN THE ****ING ENGINE,
2.- GIVE IT TO SOMEONE ELSE FOR DONATION PURPOSE
3.- AND FINALLY, BUY A NEW ONE.
I hope these recommendations be useful for you!

Truly yours,
MAMAGUEVO

[Mr. Ed]

Mama...

Granted that was your first post ... but I sure hope your second is a little more constructive.

[smokey]

Mr. Ed You have described my problem almost exactly. I first had this problem at the beginning of last season. I brought it to a dealer for service and after a $600 bill not including parts the motor was running great.
fast forward to this season and I'm having the same problem. When I had the service done the mechanic said he rebuilt the carb and that I didn't winterize it correctly. maybe I did maybe I didn't but I doubt the carbs need rebuilding after only 1 winter and last winter know I did it right. It ran fine for 4 trips this spring and now I can't even get it up on plain. and now it won't idle either. I'm stumped and I really don't want to bring it back to that Fin dealer he's not a vary nice guy.
I hope you find your problem and please report what you found and how you fixed it. If I find the solution first I'll post it for you and anyone else with this problem.

ps. I don't think it's the new e10 fuel cause I already drained my in board 20 gal. tank and the problem remains.