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[Spawn Sack]

So I have two, four-stroke Yamaha outboards for my 12 foot lake boat. A F8 and a F2.5.

The 8 runs great in the lower mainland and the interior (generally 100mile area). I like using this motor on bigger lakes, usually trolling downriggers for kokanee. Such a great motor. Smooth as butter throughout the entire RPM range. Will plane my boat at 15mph with 2 adults and 2 dogs. Downsides of this motor are it's a heavy pig. Close to 100lbs. Boat goes on roof of truck so motor has to be lifted on/off every use. I can do it, but it's bugger esp on uneven/slippery terrain. The 8 also trolls a bit fast for trout, esp if trolling flies. I end up bumping it into neutral a lot to get the presentations to slow down/sink. I think it'll troll 1.4-1.5 mph at lowest throttle. Ya I know I could troll a bucket or change props but I like the way the motor performs with the current prop.

The 2.5 is great for smaller lakes. It's super light 35lbs or so. Built in 1L fuel tank which will run all day no problem. It's not as smooth as the 8, but that is to be expected with 1 cycliner vs 2 cyclinder. It will troll super slow at lowest throttle, right down to 1mph. About same speed we'd troll with the electric motor (usually only use on electric only lakes).

The 2.5 unfortunatley is not as happy running at highter altitude. Starts fine, runs fine, but at least once an hour it will stall when trolling at lowest throttle. Not a huge deal, pop in neutral, starts back up 1st pull, back in business. But obviously it should not do this and it is a bit annoying.

A few questions/thoughts:

-why does this happen? I know it has to do with the carburator? Does the motor need a different jet?

-is it bad/harmful to the motor to run it at altitude when it is not tuned right?

-is it possible to have the motor adjusted WITHOUT affecting the trolling speed? If a shop is just going to turn up the idle speed screw, well I can do that. I have not touched the idle speed as I want to keep the motor where it is for RPM/trolling speed. I'd rather have the motor stall once in a while that have it troll any faster than it already does.

-Lastly, if I bring it to a shop, is it any more advantageous to have it serviced at the altitude I typically fish (100 mile) or is any shop fine? In this case I'd probably bring it to Checkpoint in Abbotsford.

I doubt it matters but I run Yamalube 5w-30 and Chevron 94 gas in both of these motors.

Can't decide if I should just leave the 2.5 as is and deal with the occasional stall, or take it in and get this issue sorted out? As already said I absolutely do not want the trolling speed to increase, even a bit faster would cheese me off.

[firstlight]

My first thought is,why are you not running an electric if you like trolling?

I cant wait to shut my gas motor off and fire up the electric to troll.So quiet and the speed is infinite.

Sorry i cant help with your question.

[JustPuttsin]

Your 2.5 is setup to run on regular pump gas,87 octane. Using 94 octane is just taking more money out of your wallet with no real benefit in my opinion with a 9:1 compression ratio. Stalling out once an hour isn't bad just a pain in the a**. Have you tried using a small amount of fuel additive occasionally? Check your spark plug for carboning. If it's burning clean I wouldn't think it's jetting. As far as oil viscosity goes I'd stick with oem specs.
As you said, and I agree, these little single cylinder engines don't run as smoothly as their larger cousin's.

[sbc hris]

Your 2.5 is setup to run on regular pump gas,87 octane. Using 94 octane is just taking more money out of your wallet with no real benefit in my opinion with a 9:1 compression ratio. Stalling out once an hour isn't bad just a pain in the a**. Have you tried using a small amount of fuel additive occasionally? Check your spark plug for carboning. If it's burning clean I wouldn't think it's jetting. As far as oil viscosity goes I'd stick with oem specs.
As you said, and I agree, these little single cylinder engines don't run as smoothly as their larger cousin's.

The advantage to running 94 is not having ethanol to gum up your carb etc. I run it in my chainsaw and small outbard. Never winterize either one, never have a problem with them come spring time.

Sorry, can't help with the OP's question. Most small outboards I have seen and used stall occasionally while trolling at low throttle, but most have been 2 strokes and it's just been acceptable behavior.

[Spawn Sack]

My first thought is,why are you not running an electric if you like trolling?

I cant wait to shut my gas motor off and fire up the electric to troll.So quiet and the speed is infinite.

Sorry i cant help with your question.

Honestly my transom is a bit tight for space for 2 motors. 11"6' Journey flat bottom. I "can" fit 2 motors and have done it several times. Just prefer to run one motor. On small lakes and obviously electric only lakes I bust out the min kota 40lb thrust. Great for day trips when i can leave home or cabin with a 100% charged battery. On multiple day camping trips I found keeping the battery charged an issue. Couldy/rainy days = minimal charge. Love the 2.5hp yammy for multi day trips. It trolls as slow as id troll with my electric, and ya it makes a bit of noise but it's a yammy 4-stroke. Not much noise.

[Spawn Sack]

Your 2.5 is setup to run on regular pump gas,87 octane. Using 94 octane is just taking more money out of your wallet with no real benefit in my opinion with a 9:1 compression ratio. Stalling out once an hour isn't bad just a pain in the a**. Have you tried using a small amount of fuel additive occasionally? Check your spark plug for carboning. If it's burning clean I wouldn't think it's jetting. As far as oil viscosity goes I'd stick with oem specs.
As you said, and I agree, these little single cylinder engines don't run as smoothly as their larger cousin's.

You are right, in the manual it does say the rec fuel is regular, min octane 86. However it does also say ethanol free fuel is recomended. It also says the motor is designed to run fine on E10 if one can not get ethanol free reg gas. Since we cant get ethanol free 87, for pretty much all my small engines i run ethanol free 91 (some gas stations have ethanol free 91, most it is also 10% ethanol though) or chevron 94 (always no ethanol). For my chainsaw, hedge trimmer, water pump, generator, law mower, jet boat and 8hp outboard they all seem to run great on this gas, and never a single start up issue. Been doing this about 6 years now. Ive stopped using fuel stabiliser. Every motor starts up right away even after sitting for up to a year. With reg gas and stabiliser always had issues when start up time came.
Now, i stopped into 100mile yammy dealer yesterday and chatted with staff about my 2.5. They said motor may just not like the 94. They said they always run 87 in these motors as do most customers and had no experience with the 94 although it "should" tolerate the 94 just fine.
Since it is the cheapest and easiest possible fix im going to try switching gas 1st. I sucked out all the 94 from the built in tank and replaced with reg 87. If the stalling issue goes away ill mix up a jerry can and just use it for this motor. Id probably also add yamaha ring free + seperate stabiliser (rec in the manual and by yammy dealer).

[Spawn Sack]

The advantage to running 94 is not having ethanol to gum up your carb etc. I run it in my chainsaw and small outbard. Never winterize either one, never have a problem with them come spring time.

Sorry, can't help with the OP's question. Most small outboards I have seen and used stall occasionally while trolling at low throttle, but most have been 2 strokes and it's just been acceptable behavior.

Ya man my small motors love the 94 too, but maybe this one does not.
If running 87 seems to fix the issue i plan to run it in this motor. I think come shut down time Id drain out all the 87, then run it out of 87 gas on the ear muffs, then put a bit of 94 in and run it for a few min on this so i have ethanol free in it over the winter.

If the problem persists id have it tuned at the 100mile yammy dealer to run better at elevation.

[jimstone]

years ago I ran chevron 94 in my boat (even though it had water/fuel filter)because it had no ethanol until i realized shell 91 is ethanol free as well. when i switched it made no difference to the main motors performance or idling but the F6 was smoother running at low rpm and idle..supervisor at costco gas pumps in abby says their hi test 89 octane they sell has no ethanol either and said the landscape guys in abby use it for their equipment. with the increasing demands for cleaner burning gas engines manufacturers have to work within very narrow tolerances to achieve EPA ratings which increases the importance of clean stable fuel. i remember reading somewhere 10 years ago that yamaha does their factory testing with ethanol free 89 octane .seems like most problems ive ever had with small motors has been fuel related. taking the motor to checkpoint for "adjustments" would be my last resort . hate spending money and crossing my fingers for results. try a different fuel and see what happens. i always ran stabilizer in my fuel and once a season dumped 2 bottles of black stp fuel injector cleaner into the 100 liter tank that ran both motors..you could check again at costco to confirm ethanol free and start there..prob cheaper than chevron 94...its 1.98 a liter in surrey

[Spawn Sack]

years ago I ran chevron 94 in my boat (even though it had water/fuel filter)because it had no ethanol until i realized shell 91 is ethanol free as well. when i switched it made no difference to the main motors performance or idling but the F6 was smoother running at low rpm and idle..supervisor at costco gas pumps in abby says their hi test 89 octane they sell has no ethanol either and said the landscape guys in abby use it for their equipment. with the increasing demands for cleaner burning gas engines manufacturers have to work within very narrow tolerances to achieve EPA ratings which increases the importance of clean stable fuel. i remember reading somewhere 10 years ago that yamaha does their factory testing with ethanol free 89 octane .seems like most problems ive ever had with small motors has been fuel related. taking the motor to checkpoint for "adjustments" would be my last resort . hate spending money and crossing my fingers for results. try a different fuel and see what happens. i always ran stabilizer in my fuel and once a season dumped 2 bottles of black stp fuel injector cleaner into the 100 liter tank that ran both motors..you could check again at costco to confirm ethanol free and start there..prob cheaper than chevron 94...its 1.98 a liter in surrey

Yes shell 91 and costco 91 are ethanol free. However, they share a hose with regular gas. How much 87 gas from the last guy is getting mixed with the 91 you are pumping? Maybe half a liter? For the jet boat with 100L tank I dont worry about it. I typically fill jerry cans with costco 91 for this vessel. If I'm filling a 5L to mix up a batch of chainsaw gas I'd rather pay a,bit more for chevron 94 with its own hose; then you know it's 100% ethanol free premium.
Costco's other gas is 87, not 89 as you stated. And it says right on the sticker by the 87 button "may contain up to 10% ethanol." Therefore, I consider Costco's 87 no better ethanol-free wise than any other gas station. I think with 87 it is more important to run fresh gas and add stabilizer it if may sit in the motor/carb(s) for while when not in use.
To me the cost difference between 87 and 94 is moot in my 2.5hp. The motor burns about 100ml of gas per hour. But if it runs better on 87 then I will switch to it with ring free + stabiliser added.

[Nitroholic]

https://www.pure-gas.org/index.jsp?stateprov=BC

[Spawn Sack]

Update: for last 5 or so hours of camping trip I ran the motor on 87 instead of the 94. The motor is definitely a bit happier. Idles a bit smoother, sounds happier at WOT. Ran fine for hours and I thought the occasional stalling issue was gone, but nope it still stalled a few times.
Bought some Yamaha ring-free and Yamaha fuel stabilizer/conditioner. Next time I use the 2.5 which will be in 5-6 weeks I will add these and see if they make any additional difference. If the issue still persists I'll probably have the motor tuned for elevation at the 100mile Yammy dealer as this is the area/elevation where the motor is used most.