New to me motor not getting to full speed.

[thawk]

Hello
Looking for some help.
I just bought a used 8hp Yamaha 4stoke and a 12 ft tinny.
The motor worked great yesterday for two hours and then I was starting it to come home and it took many pulls to start. I got it going but it would only push the boat about half speed. It runs fairly smoothly at that half speed but won’t get going.

I ran it on the hose where we are staying and it started first pull and seemed fine but when I put it back in the water it will only go about half speed.

Does anyone have any suggestions? We are visiting Kye Bay for the week and I would really like to use it. Are there any good boat motor mechanics in the Comox valley area who might have time to look at this?

Thanks
Angus

 

[robertg]

sounds like a carb issue, go to lordco and get some seafoam, put it into the fuel tank and run the engine for a while see if that helps, other than that try Parker marine

 

[Buckethead905]

Get a can of Seafoam and a few cans of brake clean. Take the carb off and remove all the jets. Soak them in the seafoam for a few hours. After that’s done take your brake clean and blow out all the jets and the passages from the accelerator pump etc. Should run like new.

Bucket

 

[Ringo]

You got great advises here. I would dump the old gas in my truck and fill with either Shell 91 or Chevron 94 (non-ethanole fuel) and then add some seafoam for the mix. It’s either a problem with old/bad fuel or gummed up carb jets. you can find Seafoam at crappy tire or princes auto as well.

 

[thawk]

Thanks guys
Is taking the carb apart and re assembling something that is easy for a carpenter or do you have to be motor savy?

 

[Ringo]

I would start with the seafom and fresh gas first. Most of the times that would take care of the issue. Make sure you run the seafoam mix for a couple hours and run it in full throttle for a few minutes if you can. It’ll smoke like heck but then it’ll run way smother at the end. Good luck. Let us know how it goes.

 

[Tightlines22]

Lots of videos on Utube if you need to take the carb apart.

 

[fish brain]

Super easy. Going slow and being really careful, it shouldn't take a novice more than an hour start to finish.
When you take the jets out screw them in first, not tight-just till they bottom out. Count how many full turns you screw them in (usually 2 1/2) then when you re install them put them in until they bottom and back them off the original no of turns. Put everything back in the exact hole it came out of. I use a clean rag or shop towel lay it on the bench in front of my work space. Bits from the left side of the carb go on the left side of the rag, bits from the right go on the right. Same thing for the top and bottom bits. There are not many, so it's not hard to keep track of. Don't forget the plastic plug in the top of the carb pry it out and there is a jet under it.
I can take mine apart with a 10mm socket a Phillips screwdriver and a smallish flat head screwdriver.
As mentioned earlier there are lots of good videos around.

 

[Clint r]

Only thing I’d add is to take pictures. Lots of pictures.

 

[gungadin]

The above is most likely your issue, bud do check the vent on your portable tank to be sure it is open.

 

[doonhamer]

yea all of the above , I'd take a look at the main jet first , find what is spec , and reset ,somebody may have been tuning . also prop ? standard ?and as always .. change the plugs

 

[Fish Camp]

Start the motor and with insulated pliers remove one spark plug lead.if motor stalls you know the second plug is not fireing.Restart and remove second plug lead if motor keeps running you know its the second plug ,wire ,wire conections,coil,brain box.all those wire conectors must be taken apart and cleaned before you tackle the carb rebuild.

 

[doonhamer]

Start the motor and with insulated pliers remove one spark plug lead.if motor stalls you know the second plug is not fireing.Restart and remove second plug lead if motor keeps running you know its the second plug ,wire ,wire conections,coil,brain box.all those wire conectors must be taken apart and cleaned before you tackle the carb rebuild.

that should show when pulling the plugs , they should have same colour and condition

 

[thawk]

I got the Seafoam today. Changed the fuel out completely, changed the fuel filter, added the sea foam to the gas and ran it on the hose for a while. Started first pull every time on the hose. Took the kids out for a ride and a fish started a few times with no issue and then it took 10-15 pulls to get it going coming home.

Started the motor on the beach and sucked some of the sea foam into the system. Let it sit for a bit and now I can’t start it at all.

So I guess tomorrow’s job will be to figure out how to take the lower spark plug out. The top one doesn’t look bad.

Parker marine said they could look at it in late September but that won’t help for this week.

Im off to watch some youtube videos on carburetors.

 

[Burban]

Have you tried draining the carb bowls yet? Remove the drain screw and a couple pumps of the primer bulb should push any water in the bowls out

 

[fish brain]

I got the Seafoam today. Changed the fuel out completely, changed the fuel filter, added the sea foam to the gas and ran it on the hose for a while. Started first pull every time on the hose. Took the kids out for a ride and a fish started a few times with no issue and then it took 10-15 pulls to get it going coming home.

Started the motor on the beach and sucked some of the sea foam into the system. Let it sit for a bit and now I can’t start it at all.

So I guess tomorrow’s job will be to figure out how to take the lower spark plug out. The top one doesn’t look bad.

Parker marine said they could look at it in late September but that won’t help for this week.

Im off to watch some youtube videos on carburetors.

It's almost definitely a carb issue. Do as Burban said and drain the carb, it might just be water. Otherwise take it apart and clean it properly. its not that hard to do.

 

[bpsuls]

The carb on that motor is simple to disassemble, I'm very familiar with it (I have a t8). However a couple pointers. Sometimes the jets get stuck in there pretty good and are made of relatively soft brass. The pilot is particularly challenging at times, is easy to damage (don't ask me how I know) and costs almost 50$ to replace (don't ask how I know that neither!) That said you are not seemingly having idling problems so probably not that. Don't remove it unless you need to. Do the main jet to start with. There is a small metal plate on top of the carb with 3 screws, the gasket beneath it will likely self destruct when you remove it as it usually does that. I don't think you necessarily need to remove it yet but assume you'll need a new gasket if you do.

 

[thawk]

Thanks guys
I managed to use the motor in half speed all week and did not attempt the carb clean while away from my shop with limited tools and no knowledge. I was to worried that I would not get it back together and lose out on the week of fishing with the kids.

Now that I’m back home I will try to get it going again as soon as I catch up on work.

Definitely was worth the slow trips out with the kids They caught tons of fish.

I will update when sorted.