115 Yamaha Troubles and a Ruined Vacation

btompkins

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Aug 8, 2005
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I posted to the forum earlier in the week about my 115 1992 Yamaha, I'm more confused than ever, so I thought I'd retell the whole story to see if anyone knows what may be happening.<br /><br />I trailed my newly bought used boat from VA to NH for a two week vacation (or so I thought).<br /><br />Boat worked well for two-three days, then became troublesome to start. After a start, it worked well all day until the next morning, when it was again hard to start.<br /><br />After two days of flooding and very difficult (1 hr) starts, it finally wouldn't start at all and drained the battery from trying.<br /><br />I brought it to a Yamaha dealer in RI, who said that the problem was a bad CDI. He replaced the CDI with a used one, which was only 1y old. He charged me 270 parts + 180 labor to replace the CDI.<br /><br />I took the boat out, and it started fine, but at around 4,000 RPMs to about 5,000 towing the kid on a tube, it would stutter, felt like it was skipping or misfiring on a cylender.<br /><br />I called the dealer, and he said that the carb had a plugged jet or high speed valve. Took it back to the mechanic, and he re-built the carbs, but noted that they were clean, so he wasn't sure what the problem was... Charged me another hours labor.<br /><br />I put the boat in the water again, and it does exactly the same thing, stutters at around 4000 rpms. <br /><br />I have to leave the area and go back to VA and back to work. <br /><br />I'm very afraid that the CDI unit he replaced is causing the problem but he swears up and down that it isn't...<br /><br />Has anyone run into this problem before, and do you think it could be a bad CDI? <br /><br />Thanks in advance,<br /><br />Brendan
 

rodbolt

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Sep 1, 2003
Messages
20,066
Re: 115 Yamaha Troubles and a Ruined Vacation

have you checked the fuel pump diaphram? it does not last forever. its really odd to see a CDI failure on that motor. it happens but its rare. for 270 you could almost buy it new.
 

btompkins

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Aug 8, 2005
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Re: 115 Yamaha Troubles and a Ruined Vacation

I do have the old CDI, is there a way to test it to make sure it's okay? <br /><br />The mechanic said that the ohms coming out of one of the connectoins was very low, but if it was never the CDI to begin with, I'd like to get my money back. It looks like an easy part to replace... It did start much better after replacing it, and there definitely was an intermittent spark problem to begin with (hence the flodding)<br /><br />The fuel pump diaphram couldn't have caused the spark problem, right? But could the fuel pump diaphram cause that weird stutter only between 4 and 5K rpms?
 

btompkins

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Aug 8, 2005
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Re: 115 Yamaha Troubles and a Ruined Vacation

Rodbolt... Just noticed that you're in Kitty Hawk. I'm down there often, do you have a shop there?
 

rodbolt

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Sep 1, 2003
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20,066
Re: 115 Yamaha Troubles and a Ruined Vacation

not really anymore. I mostly contract for several marinas. I did have for years but I got fed up with the general public. if your tech did only resistance checks and not input/output voltage checks he is a rather poor tech. I never trust just resitance. loaded inputs and outputs are a positive indicator of if the syatem is working. however I work daily beside techs that have no meters or are terrified of them cause they wont teach themselves how to use them. its very simple but you must understand several things are happening at once. yes a bad diaphram can cause all sorts of things. so can dirty carbs. so far there is not good tests for the CDI that I have found other than a CD-77 and a dyno or a test wheel. with those tools I can find most problems within 30 min. the odd intermittant one excluded :) . there is a good tech in portsmouth. troy marine.<br /> tell him a guy in kitty hawk that used to work with him at the dock box says hi<br />he will take care of ya.
 

btompkins

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Joined
Aug 8, 2005
Messages
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Re: 115 Yamaha Troubles and a Ruined Vacation

Rodbolt, <br /><br />One last question. This is just a wild guess, but could the stutter at 4000 rpms be the same problem as the no spark initially, and the mechanic just wired the CDI up wrong? <br /><br />What I mean is this - could he have flipped the electronics that are used to start (coil feeds I would imagine) with those that are used at midrange speeeds or when switching from the low to high rpm coils? <br /><br />Thanks again, and I'm going to call troy marine next week.<br /><br />-Brendan
 
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