Tinny on a budget

[efendy]

The bolts can snap because corrosion can lock the threads in place. It can happen to any bolt on an outboard but particularly in the exhaust plate bolts; they have raw water running under the plate and also the hot exhaust may contribute.

I'll see how I go with this. I might get help from the mechanic for this due to the reason you mentioned above

Yep, back/forward flush through the thermostat opening.

Understood, thank you.

At high idle (<1500rpm) on the hose you should be able look for hot spots after she has warmed up with your thermometer.

Sure, I'll do this and report.
Thank you for all the help again.

[efendy]

I have some updates for the boat!

I brought in a mobile mechanic who did a compression test, listened to the motor and checked the hull briefly etc.

Compression came up at 90psi for each cylinder while cold and when warmed up dropped to 80psi for all cylinders.
He said it's low but should be able to push the boat.

Unfortunately, I wasn't able to flush the motor as directed above or look for hot spots but changed the thermostat and the gasket with genuine parts. The tell tale provided constant stream of water when I tried.
I took it to a lake yesterday with a friend who showed me how to launch and retrieve which all went smoothly.
first 30 minutes the boat ran OK and was afloat the whole time :D. it goes onto plane quickly but the motor doesn't sound normal my friend told me (I am not experienced enough to describe this). It was shaking the whole boat when the throttle was up. I don't know if this is normal.
He commented that the steering was smooth but I found out that the steering was off centre which I guess can be adjusted easily.
it stalled at idle a couple of times when we stopped in the middle of the water.
when came close to the boat ramp to get one more passenger, it started to stall more frequently. At idle it works but when you try to switch it to throttle it stops.
While the hull is very good the motor is probably not and needs some mechanic to look at!
I don't know what would be causing this problem but it was probably too good to be true for $2100!
Cheers

[skronkman]

Most outboard motors don't have a spec for the compression other than all cylinders should be within a few psi of each other. It does sound a little low but if they are even then it may not be an issue at all. It sounds to me like your engine is running uneven, likely being starved of fuel in one cylinder. This will cause rough running and shakes as well as stalls under load.

I'm assuming you have multiple carburettors. I can't remember what motor you have though.
How old was the fuel you used? Was it already In the tank? Tanks clean? Fuel lines looking good, not perished? I think the next step would be fresh fuel and the carbs cleaned. Cleaning them and putting me back together isn't difficult but you will have to balance them and tune them again when you've finished. You'll need a special tool for balancing (manometer) or get it done by an outboard mech (or motorbike mech if more handy to you as they are also familiar with multi carb engines).

Sometimes you can test out the fuel starvation theory by getting the motor running and under load (on the water, possibly still on the trailer if you want) and starting to show signs of starvation (not running right), then ever so slightly add choke and see if it improves the running of the engine. If it does, it's a sure sign of fuel starvation.

Good luck bud, don't give up on it just yet, engines sitting around unused can have many little issues that are a pain but not always expensive or difficult to fix. If it's got even compression and its cooling properly I reckon you still have hope.

[efendy]

Thanks again skronkman, I really appreciate the help!

Most outboard motors don't have a spec for the compression other than all cylinders should be within a few psi of each other. It does sound a little low but if they are even then it may not be an issue at all. It sounds to me like your engine is running uneven, likely being starved of fuel in one cylinder. This will cause rough running and shakes as well as stalls under load.

Yes, the readings were even 90 and then 80 when warm. At least, this is good. even though I don't have any experience with boats, the motor seemed powerful enough to push 2 people well.
When he did the test, the throttle was on idle. I read on the internet the throttle should be at full to get a better reading? I am considering buying a compression tester to try different combinations. I think I have to own one, they are cheap and I got myself into B.O.A.T anyway!

Regarding the starvation of a single cylinder, it is very plausible considering all the symptoms are present with my motor.

I'm assuming you have multiple carburettors. I can't remember what motor you have though.
How old was the fuel you used? Was it already In the tank? Tanks clean? Fuel lines looking good, not perished? I think the next step would be fresh fuel and the carbs cleaned. Cleaning them and putting me back together isn't difficult but you will have to balance them and tune them again when you've finished. You'll need a special tool for balancing (manometer) or get it done by an outboard mech (or motorbike mech if more handy to you as they are also familiar with multi carb engines).

I had around 4 litres of 2 months old fuel and I topped up with 16 litres of fresh fuel before heading out. the old fuel was in the tank for 2 weeks. the pressure relieve outlet on the tank was open all the way. tank is very clean and supposed to be brand new and looks new. fuel lines and the bulb look all good and new. However, this boat was put together by somebody who I am guessing is not very experienced in boats so there might be a fault or a newbie mistake somewhere.

Regarding the carbs, the previous owner told me that he got carburetors cleaned at a yamaha dealer last year and he didn't run it much after the cleaning. May be they had the same problem and thought the culprit was the carbs and got them cleaned but in reality it's something else? a bit far fetched? I will give him a call tomorrow to ask if something like this happened before.

Sometimes you can test out the fuel starvation theory by getting the motor running and under load (on the water, possibly still on the trailer if you want) and starting to show signs of starvation (not running right), then ever so slightly add choke and see if it improves the running of the engine. If it does, it's a sure sign of fuel starvation.

I will try this. Sounds like a great way to test starvation. I don't think I will have the courage to do it on water but I would do it with muffs. Under load means throttle is engaged?

would there be any adjustment I would play with? This is the same motor and issues sound similar and the got it fixed by adjusting carbs? is this something I should attempt to do?
http://www.yamahaoutboardparts.com/foru ... 25360.html

Good luck bud, don't give up on it just yet, engines sitting around unused can have many little issues that are a pain but not always expensive or difficult to fix. If it's got even compression and its cooling properly I reckon you still have hope.

Thank you for the encouragement! I have many hobbies and I always started small and cheap which made me learn things that I wouldn't if I started with new and expensive. and it's a cherry on the top if I get help from people like you

Thanks again!
Cheers

[skronkman]

If you just want to get on the water then take it to a reputable outboard mech and let him diagnose and fix. Having said that, if you're like me then that's no fun, so....

Throttle should be fully open when testing compression and the ignition off (spark disabled on the primary side of the coil).

Under load means the engine is doing actual work. You can't do this on the muffs. You need to have it in the water so it is pushing the prop against the water. You can keep it on the trailer and just back down the ramp till the prop is submerged and run it there. This simulates real world running conditions.

Are all the fuel filters clean? Does the fuel bulb get hard after a few pumps?

Tuning multi carbs is not a beginners job. It's almost more of an art than a science. I did teach myself but it came with a lot of swearing. Better left to an experienced outboard mech unless you really want to go it alone. A single carb engine is pretty easy to tune but the multi carbs are a a lot more finicky to get right. Perhaps you could talk to a friendly mech about you pulling the carbs down,cleaning and rebuilding and getting him to do the tuning and balancing to save some labour $$$. There are some initial adjustments and procedures that may require you to have the service manual handy, check online for a pdf copy of the manual for your model. Don't go playing with screws on the carbs for no reason. You'll also want a few cans of carby cleaner and a compressor with air gun.

If any fuel is left in the carbs for a decent amount of time and the engine isn't used (as little as months) it can gum them up pretty good and require them to be cleaned again. It's a common problem after boats have been laid up over winter without being winterised properly.

[skronkman]

Sometimes you can just drop the bowls off the carbs (without removing carbs from engine) and squirt around with carby cleaner and it might clear out a gummed up blockage. This requires no tuning or balancing afterward because you didn't adjust anything. It's pretty easy and cheap to do. it doesn't always work but might be worth a go and you get lucky.... The fuel pump on the side of the engine is pretty easy to do the same to, unscrew, clean, replace. Just in case. Should be able to do that in a afternoon and under $20 with basic tools. It's no magic bullet solution but you sound curious enough to try a cheap, no harm solution and you'll learn a few things on the way. Good luck man.

[efendy]

Sometimes you can just drop the bowls off the carbs (without removing carbs from engine) and squirt around with carby cleaner and it might clear out a gummed up blockage. This requires no tuning or balancing afterward because you didn't adjust anything. It's pretty easy and cheap to do. it doesn't always work but might be worth a go and you get lucky.... The fuel pump on the side of the engine is pretty easy to do the same to, unscrew, clean, replace. Just in case. Should be able to do that in a afternoon and under $20 with basic tools. It's no magic bullet solution but you sound curious enough to try a cheap, no harm solution and you'll learn a few things on the way. Good luck man.

Thanks again Skronkman, I appreciate it.

I inspected the motor a bit today. Lines look pretty good. actually they look new. Overall motor looks pretty clean too.
I opened up the thermostat and there was residual amount of sand in the cavity. I still want to flush it as you described in one of the earlier posts and also look for hotspots on the block.

I opened up the fuel filter and it looked very clean with only a few spots of dirt on each filter section. I cleaned these with my finger and put it back.
All levers on the motor look very clean and greased. It's apparent that some work have been done on the motor.
As I said earlier, spark plugs look clean.
One thing I forgot to mention was when the mechanic checked spark end of the spark plugs, one out of three looked cleaner. is this something to worry about?
Carbs (3) look pretty clean outside. Of course they get dirty only inside I think I will follow your suggestion and clean them with carb cleaner without removing them and also clean the fuel pump and see how I go. Otherwise, I'll take it to a good mechanic to fix it as the summer is ending!
Yes, it's all about diy and learning as I fiddle with things. There is no turning back for me as I will always have a boat from now on :a_goodjob: it's good to learn basic maintenance so I can channel the money I save towards more useful things such as lures and reels :rofl:
Cheers!

[skronkman]

Maybe the plug was newer than the others? It could also be a sign that that cylinder is running a different mixture than the other 2 which could point back to a fuel starvation issue on one cylinder. Get yourself 3 new plugs that are the correct ones for your motor (check manual) and keep the others for spares. This will eliminate them as a source of trouble. It's also worth doing a resistance test on your coils to ensure they are all the same resistance between the same points on each wire on the coils. You'll need a multimeter for this, just check the high tension and low tension sides for resistance and compare with the same on the other 2, they should all be similar readings for similar tests.

It is also possible that water is getting into that cylinder via the head gasket and steam cleaning the plug! I would say it's unlikely if you have even compression though.

[efendy]

Maybe the plug was newer than the others? It could also be a sign that that cylinder is running a different mixture than the other 2 which could point back to a fuel starvation issue on one cylinder. Get yourself 3 new plugs that are the correct ones for your motor (check manual) and keep the others for spares. This will eliminate them as a source of trouble. It's also worth doing a resistance test on your coils to ensure they are all the same resistance between the same points on each wire on the coils. You'll need a multimeter for this, just check the high tension and low tension sides for resistance and compare with the same on the other 2, they should all be similar readings for similar tests.

It is also possible that water is getting into that cylinder via the head gasket and steam cleaning the plug! I would say it's unlikely if you have even compression though.

Wow, lots of great info mate. Thank you.
I have all the tools to tackle the troubleshooting tests you've recommended. I just need a bit of time and do some reading of the manual. Thanks a lot!
Cheers

[Mattblack]

Hey Efendy....you're not running the fuel mixture too rich are you? I'm pretty sure those late model (looks like an 80's model) Yamahas run a 100:1 mix ratio (triple check that though...I could be wrong). If it's running to rich, it will get oiled up whilst its running on low revs and stall...they also run pretty rough.
P.S. Sometimes it's not a bad thing to put a little bit extra oil in with the older motors...just don't over do it.