'93 25hp 2 stroke Spark Plug Issue??

[99yam40]

the primer bulb pushes fuel past the pump and into the carbs when you pump it, so you have a carb problem not a fuel pump problem

[Jason2tpa]

You're absolutely correct Dashude. And no offense taken. This has become waaayy out of my comfort zone. You guys have been so good being patient and taking time to help. Im ordering a new carb tomorrow. Do you know if when ordering a new carb it comes ready to go? Meaning it doesn't need a kit. Im ordering from Boat.net where I've gotten all other parts. Also ordering the fuel pump kit ( 1 gasket, 2 diaphragms). The body, outer metal seal of the pump, and the 2 flaps look perfect so ill keep those. Cleaned out my fuel tank. Ill let it dry on the back porch few days out of sun and rain. Also cleaned out the tube that inserts into the fuel tank that has the little filter at the end. That leaves the fuel line and bulb. Before incurring that expense because they are fairly new, ill wait till all new components are installed. If there is still a fuel issue ill know what it is.

So thats that...for now. Any other suggestions as far as eliminating fuel issues and preparing to install new components please let me know. I'll probably get the new stuff by end of week. Keep yall updated once I do. And again, big big thanks!!

I guess not replace, but you seem to have ecountered a few issues with the tank/vent/disconnects, no?
The other odd thing is the firm bulb after it was disconnected from the tank while you were running on the water vs a soft bulb with the line disconnected on dry ground.
I'd expect opposite results.

We've all gotten deep into this, only to discover midway through that you've left out some very important details - several rounds talking about it being hard to start - only to find out later that you left out the part about the missing choke flap.
That was a hugely important element needed to help you.

Honestly though - and I'm not trying to be mean or condescending - your in over your head with this thing. You don't have the experience required to trace the problems accurately, convey your findings to us, or the hands on technical skills (yet) to work through some of these problems to arrive at a reliable seaworthy motor.
Twice now this thing has left you in undesireable positions on the water, perhaps even dangerous positions with outflow tides.. and it still doesnt have the basic requirement of having the second choke flap installed.

I really suggest you take it to someone who works on outboards regularly, have them go through it, then they test it on water, then instruct you on its finer operating details.

[Dashunde]

Im ordering a new carb tomorrow. Do you know if when ordering a new carb it comes ready to go? Meaning it doesn't need a kit. Also ordering the fuel pump kit ( 1 gasket, 2 diaphragms).

Not sure exactly what engine model you have, but they all seem to come assembled and complete.
Is it the upper or lower carb your replacing?
The lower appears to already come with some sort of pump attached to it.
(Fuel pump? The descriptions for Yamaha parts leaves a lot to be desired on all of the parts sites.)

You'll still want to take both carbs off and be sure the floats are set level with the carb casting... and you'll also need to sync both carbs - they need to fuel each cylinder equally throughout all phases of operation.

I really recommend you have a Yamaha tech, or at least a tech with plenty of multi-carb experience set these two up for you.
You dont want one running lean while the other is running rich, or some other difference between them... a situation you may very well already have.

Good luck, let us know how it ends up.

[Jason2tpa]

Upper carb. I'll have to order the pump parts separately. Most definitely have my mechanic do the dual carb setup.

Not sure exactly what engine model you have, but they all seem to come assembled and complete.
Is it the upper or lower carb your replacing?
The lower appears to already come with some sort of pump attached to it.
(Fuel pump? The descriptions for Yamaha parts leaves a lot to be desired on all of the parts sites.)

You'll still want to take both carbs off and be sure the floats are set level with the carb casting... and you'll also need to sync both carbs - they need to fuel each cylinder equally throughout all phases of operation.

I really recommend you have a Yamaha tech, or at least a tech with plenty of multi-carb experience set these two up for you.
You dont want one running lean while the other is running rich, or some other difference between them... a situation you may very well already have.

Good luck, let us know how it ends up.

[Jason2tpa]

UPDATE!!.....'93 25hp 2 stroke Spark Plug Issue??

Hey gang. New carb and fuel pump innards installed today. Started on 1st pull of flywheel despite not being touched in over a week. I duplicated the scenarios that were giving the engine problems (pulled fuel plug while idling then let it run out of gas). Plugged fuel back in. Started without a problem. Going to water test here shortly.

I've attached a picture (hopefully I attached it correctly). After inspecting the new carb (upper---top carb in the picture) I noticed that the choke flap orientation on the lower carb was different. Obviously the carb that came direct from the manufacture is correct. Remember, I bought this engine on Craigslist and had to replace a few things on the engine (including the carb). No doubt whomever had this engine before me had no idea what they were doing. So my assumption is they removed the choke flap and when reinstalling they reversed it?

Anyway, the engine started no problem despite this difference in choke flap orientation. But will this be a problem in the future?? I really don't want to remove those 2 screws attaching the choke flap to the rod because they flare (difficult to get back in...and it's a very small thread). Your thoughts? Dashunde, Townsend...you guys know your stuff. What do you thinK?

[99yam40]

I normally don't say this, but I told you so
Once you have all the parts to choke in there it can finally function

Hard to believe someone took it apart that far, but who knows what happened.
But if it starts and runs fine I would leave it alone, the choke is opened up while running so it should not affect anything IMHO

[TownsendsFJR1300]

But if it starts and runs fine I would leave it alone, the choke is opened up while running so it should not affect anything IMHO

I agree ^^^...

Your only using the choke for several minutes then you don't even need the plate.

If I was you, I'd leave it.

If it was mine, I would have put the old carb back on with the plate you already had but that's moot anyway. Glad its running dependably again..


You should be good now and NOT nearly as touchy, starting cold.

Bring an anchor just in case....

[zenoahphobic]

I agree ^^^...

Your only using the choke for several minutes then you don't even need the plate.

If I was you, I'd leave it.

If it was mine, I would have put the old carb back on with the plate you already had but that's moot anyway. Glad its running dependably again..


You should be good now and NOT nearly as touchy, starting cold.

Bring an anchor just in case....

Choke would not be on for even a minute unless you are at very low temp.

Jason2tpa was the carby just bolted on? were not people saying this is a tricky two carb setup (need fancy tech)!

[Jason2tpa]

So you guys agree...the lower carbs choke flap is indeed backwards? So weird. Im not gona touch it. Theoretically, i wouldnt think it matters whether air enters at the top of choke throat or bottom.

Zeno....I think It was suggested I have a mechanic dissemble the lower carb to inspect before installing with the new upper carb. And i would have complied bc Ive never dissembled and cleanned a carb before. However, me being the learnid guy I am, I watched a great youtube video of cleaning the exact model carb. I used the bad carb i removed for practice. Turns out it's incredibly simple. Also suggested a mechanic sync the two carbs once i installed but I had been comfortable doing this already. Having the opportunity to dissemble-assemble the old carb was a fantastic learning tool. Now Im familiar with its innards.

Water tested last night. Ran perfect. Not one sputter, hiccup, bogg, or any likeness. Lets hope this will close the door on all the major issues with this engine. Maintenance from here on out fingers crossed. Thanks again every one!!

[TownsendsFJR1300]

The choke butterfly hole allows a little bit of air thru when closed.

With it correctly installed, theoretically, your getting a little more fuel as that hole is slightly closer to the float bowl, float, etc, allowing very slightly more fuel(slightly higher vacuum near the float bowl).

If its running good and it starts all the time cold (once you have the method down), I'd leave it...

As you've probably noticed, with both carb chokes working, it doesn't take much to start cold...

BTW, when / if you ever go to fuel injection, its's really odd initially to not go for the choke, raise the idle a certain amount, etc. Just turn the key like a new car, nothing else to do but wait for the idle to come down (warmed up).

**You do STILL want to read up and sync the throttles so both cylinders are pulling the same for best performance.

[99yam40]

The carbed motors with prime start systems also do not need anything from the guy starting the motor except pumping primer bulb and turning the key.
Just to let people know

[zenoahphobic]

Jason2tpa glad to hear that you are learning on the job.

Sometimes it seems mechanics big note themselves on this forum. Not always clear why except that perhaps it was part of their training to look down upon do it yourselfers . I've said elsewhere that with reasonable intelligence , research and asking questions, mere mortals can achieve just as well without a professional.

Keep doing what you do.

[Jason2tpa]

Thanks Zeno!

Townsend...you're correct. Ive been running my fathers boat wirh 150 yamaha. I think ive used choke once, and that was because it was 60 degress outside (cold for tampa).
I synced both carbs and set idle speed to specs. Running great. I definitely need to change props though. Two reasons...need a prop with more rake to lift the bow. Ive tried everything...different engine heights, trim rod settings, shifting weight, etc. My boat, 13' stumpknocker, has a very deep V for its size. At 3/4 throttle this V starts to dig in. Boat then lists, spray over bow. Ive got a manual jack plate on too, which brings the engine weight 4 inches behind transom. So hopefully changeing props will do the job. It would be nice to have a device that does the opposite of trim tabs. Instaed of lifting stern it would lift bow. Having power tilt/trim is sooo much easier lol.

[TownsendsFJR1300]

Thanks for the update!

I'm too lazy read the entire thread again but do you have a tachometer anywhere?

Its very important to make sure engine, normally trimmed, "average gear, fuel, etc", the engines turning about 5,500 RPM's at WOT.

It'll be MUCH EASIER to into a prop shop and say here's the prop I have, I need to increase / decrease engine speed by "X" RPM's. A good prop shop can usually take care of that for you whether it be "adjusting the prop" or a new one altogether.

When I changed over from an aluminum prop to SS, that's exactly what I did and the prop shop dialed it on the money..

[Jason2tpa]

Yes I do have a tach installed. It averages 5500-5700 at WOT. The owners manuel says max operating is 5500-6000. Though I'm not trying to increase engine speed. I'm trying to get the bow up. As I increase throttle the bow goes down, naturally. But even at 3/4 throttle the bow drops down too much. I'd say of the 13' only 3' is out of the water at WOT. It needs to be more like 6-8'. Remember, as you decrease the amount of the boats surface area exposed to water you'll increase speed. So if I get the bow out of the water more, whether that be by changing prop or engine height, RPMs will drop and speed will increase.
It's just a matter of finding this boats trim sweet spot. It's taken awhile, though much of my time has been spent on repairing engine. Now my focus can be on how it rides.
Have you heard of the Nauticus Smart Tabs SX (Smart Tabs SX Trim Tabs). Interesting that they work passively. But I'm not sold on trim tabs being able to raise the bow, other than when plaining, which isn't a problem for this boat. Take a look at these and let me know what you think.

Thanks for the update!

I'm too lazy read the entire thread again but do you have a tachometer anywhere?

Its very important to make sure engine, normally trimmed, "average gear, fuel, etc", the engines turning about 5,500 RPM's at WOT.

It'll be MUCH EASIER to into a prop shop and say here's the prop I have, I need to increase / decrease engine speed by "X" RPM's. A good prop shop can usually take care of that for you whether it be "adjusting the prop" or a new one altogether.

When I changed over from an aluminum prop to SS, that's exactly what I did and the prop shop dialed it on the money..