Logo
FULL SITE MENU

Is My Motor In Failsafe Mode

M

mojack

Member
"Hi All, I just found this for

"Hi All, I just found this forum and I think it is great! I just purchased a used 40 hp Yamaha 4 stroke 1999 vintage about two weeks ago. Had the carbs removed and cleaned as it wouldn't idle well. When I took it out for sea trials the boat porpoised so bad I kind of had to limp home (installed hydrofoil next day). I took the boat out later and got to move well (full throttle for about 5 minutes- 2 times then it would bog down for a few minutes and would "catch" and go again a couple of times). AFter that it would only go about 1000 rpms, anything more than that and it would bog down, let up on the throttle and it would kick back in at about 1000 rpms. Fuel line bubble tight, no obstructions. Here's the thing, when I turn the key on I get no "chirp" and I can't even get the temp sensor connector to ground out on the block to make it "chirp". The horn does work because I hooked it to the battery directly to check. Any thoughts/insight greatly appreciated!
Derek"
 
side mounted control box. I e

side mounted control box. I even tried unconnecting part of the wiring harness underneath the cowling and tried to ground the pink wire and still nothing. I don't want to just start replacing parts but I think there may be something going on with the CDI. I don't know if there is any kind of diagnostic computer for these outboards.
Derek
 
"I didn't mention that whe

"I didn't mention that when I got the motor, I noticed that there was a connection that had been taken apart so I put it back together (these things don't come apart by themselves). I didn't realize it at the time but this particular connector held the pink wire that goes to the temp sensor. When I installed the motor I purchased a new 703 control box. I have not checked for continuity yet but will do that this weekend."
 
I think the continuity is OK.

I think the continuity is OK. I tested the temp sensor and it read about 4 ohms. Shouldn't this give a reading of clear or hard short with no in between?
 
"I do not have one yet. Do yo

"I do not have one yet. Do you know where I could get one for this particular motor? I don't want one of the Seloc manuals. Oh, checked on the temperature sensor and wiring. All are OK there. Mechanic thinks he needs to remove and clean the carbs again. We are going to go for sea trials tomorrow so he can see exactly what it is doing. I'll keep you posted."
 
Please forgive my ignorance.

Please forgive my ignorance. I don't know what the LIT # is. The model is a F40TLRY. Is this what you were refering to?
 
They are out of stock. Shucks

They are out of stock. Shucks! The mechanic really thinks that it is still something in the carbs as the bog down occurs right when going from the idle jets to the regular jets. He took the carbs off on Thursday and said he wanted to soak them over the weekend then put them back on. I really hope this is the problem.
 
"Way too late. They were put

"Way too late. They were put in bath Thursday by a certified Yamaha tech. I imagine you are concerned about the seals and gaskets. He supposedly removed all of them before soaking. Why do you say not to soak???
I won't have the LIT number until I get the boat back, hopefully some time on Wednesday."
 
wow as a certified tech he soa

wow as a certified tech he soaked them?

the marine carbs have a coating on them to protect them form moisture build up

well he just took that moisture protection right off
 
"well, he's supposed to be

"well, he's supposed to be a certified tech. can the moisture protection be reapplied somehow? Will this adversely affect the carbs (worse than they already are?)."
 
"He took them off on Thursday

"He took them off on Thursday and said he wanted to soak them over the weekend. If I use the yamaha fuel treatment regularly, will I be OK? What purpose does the moisture protection provide?"
 
he said that he thought that t

he said that he thought that there was still something (trash or varnish) still in the jets keeping them from working properly. We took it out Thursday AM and I was able to show him what it was doing (when throttling up and apparently going from idle jets to other jets and bogging during the transition). We were able to get it to full throttle for a few minutes two times but after a few minutes it would bog back down and we would have to throttle back to the idle jets. Does this sound reasonable to you? Could this be a problem with the computer or power pack?
 
hopefully all he did is take t

hopefully all he did is take the jets out. I'll find out later today. I'll let you know. Thanks again for all of your input!
 
"OK, just took it out for sea

"OK, just took it out for sea trials. It ran 95% better than it did before the carbs were cleaned. The mechanic said that the bottom carb showed some signs of corrosion. The mechanic also said that the carbs still need to be adjusted individually. He said that there was some special tool he used to adjust the volume of air going into each carb. Hopefully it will be perfect after that."
 
"OK, so after the carbs were r

"OK, so after the carbs were removed twice, soaked and cleaned and then synced; the top end still bogs after about 5 minutes or so when going close to WOT. This weekend I pulled my 150 lb son on the wakeboard and it pulled him up effortlessly and would pull him great for long distances at close to 1/2 or 2/3 throttle and would never bog at that speed but as soon as you try to go over the majic RPM line, it would bog. It wouldn't completely bog down, only dropping maybe 1/3 of the power. Wierd thing is after it bogged, if you came to a stop and let it idle for a 1/2 a minute or so, it would fix it self and then you could get going again. I almost swear that this has got to be some kind of poorly designed fuel pump on yamaha's part as there are plenty of other guys with this same motor that have the same problems. I'm going to get the yamaha mechanic to go out on the boat with me to let him see exactly what it is doing sometime this week.
Derek"
 
so u have not replaced fuel pu

so u have not replaced fuel pumps
u need a to do a vacuum pressure test on the fuel lines
 
"No, I haven't replaced th

"No, I haven't replaced the fuel pump, (I think it only has one fuel pump) on the back but it has two output hoses. I'll let you know how it goes."
 
"Hi JIT,
I was just told not

"Hi JIT,
I was just told not to run 91 octane in this motor. I am going to change it to 87 this week and try it out this weekend and see how it does before I get the mechanic to go for a very expensive ride with me.
Derek"
 
Back
Top