Motor Heads - Suggestions!

[AKRISONER]

Hey Guys,

Beginning this year I noticed something was a little bit off with my 98 two stroke yamaha TLRW130. The main thing is that I seem to have lost about 3-4mph off of the top end at WOT. The motor had also seemed to maybe lost a bit of pep that I was used to. I wasnt sure if I was just getting fatter and weighing the boat down with quarantine weight. But lately ive been working out and eating right and am back in shape so its not that anymore 😆

Anyways, immediately when dealing with carbureted two strokes I think, compression, air and fuel delivery. In order of price and worrisomeness, I figured there was a chance that I was losing compression and this was causing my motor to not deliver as much power as I was accustomed to. So yesterday I took it upon myself to do a proper compression test (warmed up the motor, removed the plugs and turned the motor over on each cylinder) and thank the lord, my compression was about as close to 130psi as a person with a 22 year old motor could hope to be. Needless to say the headgasket and rings are in good shape.

So now after discussing with a few friends who are a bit more mechanically inclined I talked about what things I should consider to try and get the motor back up to speed.

First obvious choice is the plugs, but I change those every year so the current set literally only has about 20 hours at most on them. One friend mentioned the gapping, but the plugs Im running are the plugs for my outboard. I dont see how they should need re-gapping? (feel free to tell me why im wrong here, im oblivious) 

Second, is bad/weird gas...I only run premium ethanol free fuel in the boat and regularly run seafoam through. No different gas has changed anything.

One friend mentioned to check the reed valves for wear and seal. A good idea IMO, i may even upgrade these to a performance set manufactured by the top yamaha outboard performance shop in the United States. Doesnt seem like a difficult job to do once the carburetor is off.

Another suggestion is to swap the fuel filter and inspect the fuel line/replace them. (I think I am going to do this immediately, especially the fuel filter)

Finally, to simply clean and redo the gaskets on the carburetor with new gaskets using a carburetor repair kit and clean all of the jets and ports out. Ive done this on a small 15hp suzuki, with the right amount of time Im sure I could do it on the bigger yamaha. The one thing Id be scared of is simply adjusting the air and fuel spring screws once clean. Im not certain how the pros adjust these considering some are basically inaccessible while installed on the outboard. One thought is to simply count the rotations of the screws to "snug" from their current position and then try to repeat that backwards when re-installing. Perhaps they need adjustment though? Is there a bible on how to do this?

Another idea I had just from experience with my old car was a potential vaccum leak? Im not sure if thats possible on this type of motor, but is there somewhere that can be considered a "trouble spot" for vaccum leaks on these types of motors? my experience is specifically with your standard DOHC 4 stroke car. My old mazda leaked like a seive lol.

Does my train of thought seem logical? Is there anything else that you recommend that I check. At this point Im basically willing to do anything knowing that I was prepared to have the top end rebuilt, knowing that its in great shape leaves me with an almost wide open budget to tinker.

Im all ears to those that surely know far more than I do! Shoot me your suggestions!

Edited August 13, 2020 by AKRISONER

[Headhunter]

Have you looked at or tested the coils? Are they original?

HH

[AKRISONER]

2 minutes ago, Headhunter said:

Have you looked at or tested the coils? Are they original?

HH

I believe they are original. I always thought that coil failure was very very noticeable though (I had them fail on my old car, the thing wouldn’t drive!)

care to elighten me on how they could be the culprit? I’m totally open to totally replacing them and the wires! How would one go about testing them?

Edited August 13, 2020 by AKRISONER

[Headhunter]

If the coils are old, worn etc, they could lower your RPMs, miss fire or simply not fire at all. I watched Bernie (30 year mechanic) diagnose a problem with FishnSleds 115 Merc. Hanging off the transom at 40k, you could hear the coils mis-firing. It would run, sometimes smooth and others, mis-fire.

If yours are original, it can't hurt to replace them, they aren't that expensive and you will notice the difference quickly.

HH

Edit - not a Motorhead, but I can play Ace of Spades for yah on bass, if you wish! LOL

Edited August 13, 2020 by Headhunter

[smitty55]

For many years I worked on a wide variety of aviation motors, both ac and dc, that were used for small galley fans running at 20k to large fans used for cooling radio racks to ventilation systems in aircraft. The main testing done on coils in armatures and rotors was doing an insulation resistance test ( also known a a megger check) and also doing inductance testing on the armature windings. Over the years I noticed that even though some motors would pass these tests, there was a direct correlation between readings on the outer end of the tolerances and lowers speeds and higher current draw in these motors. So by changing out the armature for example, test results were much improved.

So offhand I would definitely agree with HH that it's quite possible that your coils are breaking down, if they're not that expensive and easy enough to replace it would be worth swapping them out just as preventive maintenance if not peace of mind.

 

Cheers

[misfish]

3 hours ago, Headhunter said:

If yours are original, it can't hurt to replace them, they aren't that expensive and you will notice the difference quickly.

I would concur with this. You doctor? Yes, I concur, and you doctor ? Yes,I concur.

 

😁

[AKRISONER]

1 hour ago, smitty55 said:

For many years I worked on a wide variety of aviation motors, both ac and dc, that were used for small galley fans running at 20k to large fans used for cooling radio racks to ventilation systems in aircraft. The main testing done on coils in armatures and rotors was doing an insulation resistance test ( also known a a megger check) and also doing inductance testing on the armature windings. Over the years I noticed that even though some motors would pass these tests, there was a direct correlation between readings on the outer end of the tolerances and lowers speeds and higher current draw in these motors. So by changing out the armature for example, test results were much improved.

So offhand I would definitely agree with HH that it's quite possible that your coils are breaking down, if they're not that expensive and easy enough to replace it would be worth swapping them out just as preventive maintenance if not peace of mind.

 

Cheers

When smart people are talking, I’m listening. Those coils are getting changed for sure now. Really fantastic tip.

$70 usd a pop, not bad...not cheap but much cheaper than a top end rebuild!

Edited August 13, 2020 by AKRISONER

[aplumma]

Is the complaint that it is not running correctly at WOT or is it you are not getting the same RPMs  you were? The drop in MPH could be drive train friction or prop damage. A  strike could have damage the drive train creating friction or it could have spun the shear in the hub. I  agree new coils are a good idea as the cases get old they can get small cracks in the windings and miss fire internally. We also should look at the timing and the timing advance linkage to make sure it is not binding up and that the screw that limits the advance from over advancing is timing. Both of these require a timing light as well as the specifications of the motor. The final thought is that the metering screws have debris on the end of them that needs to be flushed out. Remove the screw after counting them in and flush them out reset them the same amount they usually do not need to be adjusted to a new setting unless someone moved them. 

Art

[Freshtrax]

I agree  rpm  will tell the tale here  can you pull same rpms as past?   If its same rpm but lower speed need to look at prop, hub  or hull.  If it won't pull the same rpm you may be down on power. 

[AKRISONER]

Definitely lower RPM on the top end. I know for a fact that I haven’t hit anything. And literally no one else drives my boat because they are scared of it lol. (It’s got a lot of power for its size and definitely needs to be “driven” as they say)

i can easily rule the lower end damage idea out of it. There’s a small ding in the stainless prop but that’s been there since I’ve owned it so nothing has changed.

i also took the lower end off last year to do the water pump and the spindles all looked to be in fantastic condition with no signs of wear or anything at all.

the timing check thing might be interesting but tough for me to do with my limited knowledge.

Edited August 14, 2020 by AKRISONER

[Freshtrax]

You mentioned a trim problem earlier in the season are you sure your able to trim  All the way out?     Ie can you trim till the prop blows.  I always look for the simplest fix first.   You would be surprised sometimes.

 

 

I once dropped a fuel tank to replace a fuel pump and realized the customers car was out of gas...

Edited August 14, 2020 by Freshtrax

[AKRISONER]

11 hours ago, Freshtrax said:

You mentioned a trim problem earlier in the season are you sure your able to trim  All the way out?     Ie can you trim till the prop blows.  I always look for the simplest fix first.   You would be surprised sometimes.

 

 

I once dropped a fuel tank to replace a fuel pump and realized the customers car was out of gas...

Ya trims been fixed, aside from the pump it’s had all new seals, new fluid and a new motor. If you can’t perfectly adjust the trim on my boat it doesn’t run right. Bass boats are different than Tinners because you have to run on pad and get as much of the boat out of the water as possible.

[Chris J]

What RPMS are you turning? Add extra wight to boat by adding stuff?  Been very humid, mine loses RPMS and speed till the weather is cooler. Lower unit was apart or just change impeller?  Your plug gap should be fine if they are NGK.   If your compression is good, no idling issues or missing at WOT or any range it may be hard to diagnose.  I'd fix the ding in prop either way. 

 

My 97 150 turns a 23 p prop at 5500-to5600 in cooler weather and 5200-5400 in the humid stuff, mph varies from 55-60 depending on load and weather for me.

 

 

[Hack_Fisherman]

All great suggestions. I agree with others on coils.

have you done a decarb?

is your hull getting fouled? I just bought and sold a water stored aluminum boat that looked like it sat on the bottom of the ocean for 50 years. 

You mention gas is not bad, but is Premium right for your motor? Premium burns slower, regular is actually hotter, faster burn. I don’t believe ethanol fuels are the killer everyone complains about if you use stabilizer and use the fuel within the season. I’ve never had a problem on any of my motors. 

Lastly, is your boat getting waterlogged? (Could any of your floatation foam or floors be sucking up water causing extra weight, or leaf/debris plugged channels trapping water from getting to the bilge)

Edited September 3, 2020 by Hack_Fisherman

[AKRISONER]

3 hours ago, Hack_Fisherman said:

All great suggestions. I agree with others on coils.

have you done a decarb?

is your hull getting fouled? I just bought and sold a water stored aluminum boat that looked like it sat on the bottom of the ocean for 50 years. 

You mention gas is not bad, but is Premium right for your motor? Premium burns slower, regular is actually hotter, faster burn. I don’t believe ethanol fuels are the killer everyone complains about if you use stabilizer and use the fuel within the season. I’ve never had a problem on any of my motors. 

Lastly, is your boat getting waterlogged? (Could any of your floatation foam or floors be sucking up water causing extra weight, or leaf/debris plugged channels trapping water from getting to the bilge)

1. Definitely doing the coils this winter

2. Do you mean rebuild/clean the carb or something else? I plan on redoing all of the gaskets and cleaning it this winter (I just bought a home with a garage!)

3. Its a glass boat, A possibility that the foam is getting saturated, however the boat doesnt get stored in the water. It spends most of its time on dry land but i guess its possible? But doesnt explain why the change was so drastic from one season to the next. My assumption is that after a winter sitting in the cold and dry it would be as light as it could ever be, yet the problem started right at the beginning of the season this year. In fact the boat didnt see water until the covid restrictions lifted...after sitting for 8 months.

4. Ive never ran anything but premium through the motor with periodic runs of seafoam. If it was a fuel issue I would have experienced this for the first two years driving the boat.

5. A plug I guess is theoretically possible, but I can see down into the hull of my boat from the battery compartment and theres no evidence of that much water sloshing around in there. Also the boat has a very very slow leak somewhere, maybe a litre of water builds up over the course of 4 days, but its far from anything catastrophic because at the end of the day its a glass boat, the hulls for the most part dont leak aside from places where things have been punched through the glass.

Edited September 3, 2020 by AKRISONER

[Lostchild]

I would start with the fuel filter if you haven't changed it yet. The other thing you might want to consider is stretch in the throttle cable perhaps, not allowing quite full throttle? Just throwing ideas out there.