Yam 85 Losing Power.-

[Sea Rider]

Scenario : a nice 1990 2 stroke Yam 85 HP motor losing power after running at high revs for some time. This motor has not received mayor preventive maintenance nor convenient flushing with fresh water soon after returning to Terra Firme.

Will ask the owner if was running the motor with the tank's air vent fully opened as a starter, then check the internal fuel filter, t-stat and spark plugs condition. This motor is having continuous erratic peeing issues, needs to have the peeing hose that attaches to the lower block to be constantly removed to poke plastic cannulas inside to clear the repetitive salt accumulations going on there.

Wouldn't be surprised that the termo sensor/switch is playing tricks making the motor to go into slow safe mode due to excessive salt build ups that motor has already collected over the years of constant use and poor flushing.

Happy Boating​

 

[racerone]

Clean out the entire cooling system.----From water intake screens right to all the water jackets and covers.----Will run like new again.

 

[Sea Rider]

To start the long troubleshooting cleaned the internal and external fuel filters, were found 95% impeccable clean with excellent fuel flow from tank to carb entrance while priming the bulb hard. Removed the T-stat cover and brushed the t-stat with paint thinner including the valve pressure control and their respective internal housings.


Removed the Temp Sensor, both tip and housing were found bit rusted and fouled looking, cleaned both to mint cond. Polished all 3 Ignition Coil grounds which were found bit rusted and shinned their respective spark plug connectors. Old spark plugs in current use were found with oddly colored tips, never have seen such an awful scenario, pics peaks for themselves.



Removed the lower block's peeing nipple and squirted several shots of WD-40, let penetrate for 15 minutes and installed back the peeing hose.



Cleaned all 3 spark plug motor's threads, re-gaped 3 brand new NGK BR8HS-10 spark plugs, torqued all 3 to factory specs. Don't know why these plugs that should come out the factory well gaped to 1.0 mm were found slight over 1.1 mm.



For me a spark plug well factory gaped should not fall from the feeler gauge when turned up side down, if so it's a clear indication that comes factory gaped to slightly more that what the spark plug's container reads.

Installed muffs and motor started right up peeing strong as a teenager, craned the combo to the water, let the motor run at idle/neutral for 5 minutes, went full throttle as stealing the combo for a half hour wot run, all went well as was expected. Seems the temp sensor and housing being rusted and fouled played tricks to the motor lowering the max wot rpm due to cylinder head temp variations, a tricky fault presented only when at wot.

That 2 stroke 85 HP motor although runs full wot with 0 issues, needs a desperate long CRC decarbonizing process thru the 3 carbs with at least 1/2 to 3/4 bottle contents to regain some what its lost agility. Suggested the owner to buy a 3 cylinder induction hour/tach meter and tach the motor at wot to know what's the max wot rpm numbers dialed with current 3 blade alum prop which surely is lugging the motor down as my musician ears doesn't hear the motor revving high when lightly loaded at wot .

Will work some neat form of internal descaling the motor right and soon after going for a prop maximization to less prop pitches for the beast to run towards its max 5500 wot rpm range. That nice well built motor deserves the best in the world...

Happy Boating​

 

[Sea Rider]

Does anyone have the slightest clue why would 3 spark plugs well gaped to factory specs came out with a notorious oddly uneven colored tips ?​

Upper plug shows a greenish looking tip, middle a redish looking tip and bottom one a black carbon looking tip, You'll be wondering if it's due to cylinder compression incongruencies, nope, all 3 cylinders were found with 100 PSI even outputs.

A spark plug test made with an appropiate tester showed a strong 9 mm spark jump on all 3 ignition coils which is what Yam states for the E85B motor. Last to blame, could be a carb related issue, none have been cleaned since out of the box...

Happy Boating​

 

[QBhoy]

Scenario : a nice 1990 2 stroke Yam 85 HP motor losing power after running at high revs for some time. This motor has not received mayor preventive maintenance nor convenient flushing with fresh water soon after returning to Terra Firme.

Will ask the owner if was running the motor with the tank's air vent fully opened as a starter, then check the internal fuel filter, t-stat and spark plugs condition. This motor is having continuous erratic peeing issues, needs to have the peeing hose that attaches to the lower block to be constantly removed to poke plastic cannulas inside to clear the repetitive salt accumulations going on there.

Wouldn't be surprised that the termo sensor/switch is playing tricks making the motor to go into slow safe mode due to excessive salt build ups that motor has already collected over the years of constant use and poor flushing.

Happy Boating​

if it helps...there isn't a slow or safe mode on this engine. great engines...probably one of the best...I would suspect fuel delivery issue, as long as she has compression and is able to run well otherwise and for a period of time up until the issue shows.

 

[Sea Rider]

if it helps...there isn't a slow or safe mode on this engine. great engines...probably one of the best...I would suspect fuel delivery issue, as long as she has compression and is able to run well otherwise and for a period of time up until the issue shows.

Check first posted pic, shows where the Temp Sensor is located, when a different temp is detected triggers a signal to slow the motor down as not to overheat it, Don't know if that operation could be called a Safe Mode or not, will check with the Service Manual how it works and what it's called for a better tech understanding. Saturday plan going for a 100 Km water raid, hope all goes well, fingers crossed well in advance LOL!!

Happy Boating​

 

[Faztbullet]

That motor does not have a limiter or safe mode. The temp sensor when it reaches about 190° turn on the overheat lamp.

 

[Sea Rider]

That motor does not have a limiter or safe mode. The temp sensor when it reaches about 190° turn on the overheat lamp.

I don't think that Yamaha has installed such an extremely primitive system on ithis nice 85 HP Enduro B model which is a Commercial work horse, a loud buzzer would have been much better to hear than to see in plain daylight. Have seen none of the tiller or remote versions to have been factory delivered with such overheat lamp nowhere on the cowling or motor's front and guess what, fishermen don't use central consoles.

Although the Service Manual does mentions at which temp the TS acts doesn't mentions a thing if triggers an overheat lamp or the CDI whatsoever. Could not get a E85B Service Manual to check that out, the only one that could download from the net corresponds to the older 50G, 60F, 70B,75C, 90A versions which has nothing to do with the newer Yam E commercial versions.

Can you explain why after removing the temp sensor and cleaning it along its internal housing the motor is running great again at wot ?

Forgot to mention that this motor has never ever been run carb dry in its entire life which could account for an uneven fuel delivery in each combustion chamber to achieved those awful colored plug's tips....

Happy Boating​

 

[QBhoy]

Check first posted pic, shows where the Temp Sensor is located, when a different temp is detected triggers a signal to slow the motor down as not to overheat it, Don't know if that operation could be called a Safe Mode or not, will check with the Service Manual how it works and what it's called for a better tech understanding. Saturday plan going for a 100 Km water raid, hope all goes well, fingers crossed well in advance LOL!!

Happy Boating​

It is a temp sensor. But there is no way it limits anything. It just alarms at best. There are no safe or limiting features on this engine at all. All the best.

 

[Sea Rider]

It is a temp sensor. But there is no way it limits anything. It just alarms at best. There are no safe or limiting features on this engine at all. All the best.

OK, do you or FB happen to have at hand the 2 stroke Enduro 85B Service Manual, aside the stated working temp variations in which they act, is there any other indication about what happens when the TS detects a higher temp over its max rated for ? There were no light or audible indications whatsoever when the motor started to misbehave, as a matter of fact the motor kept running well just at a slow rpm when returning to dryland territory.

As a refference, 2 stroke Tohatsu 3 cylinder motors employs Temp Sensors as well, once a higher temp is detected triggers a signal to the CDI to lower the max wot rpm the motor was revving at to a safe min rpm, Why wouldn't a Yam Temp Sensor not behave the same ? Tomarrow will check if the TS connects direct to the CDI box in which case acts as a Rev Limiter ?

Happy Boating​

 

[QBhoy]

OK, do you or FB happen to have at hand the 2 stroke Enduro 85B Service Manual, aside the stated working temp variations in which they act, is there any other indication about what happens when the TS detects a higher temp over its max rated for ? There were no light or audible indications whatsoever when the motor started to misbehave, as a matter of fact the motor kept running well just at a slow rpm when returning to dryland territory.

As a refference, 2 stroke Tohatsu 3 cylinder motors employs Temp Sensors as well, once a higher temp is detected triggers a signal to the CDI to lower the max wot rpm the motor was revving at to a safe min rpm, Why wouldn't a Yam Temp Sensor not behave the same ? Tomarrow will check if the TS connects direct to the CDI box in which case acts as a Rev Limiter ?

Happy Boating​

I don’t have a manual I’m afraid. But I’ve known loads of these era of Yamaha engines. Had loads and have 3 of that era currently. At that age, they just don’t have any sort of protection like that on them. You can literally scream that engine full throttle with no cooling to it…and it will keep screaming until something goes bang. As it happens…I was witness to such an event with a same age 225 yam V6. Lost its water pick up at 70 mph sustained. Didn’t end well. There was no limiting intervention at all. They just don’t have it back then.

 

[Faztbullet]

Post the engine plate as don't see a 85B engine listed. And yes, I have the 85A manual. The pink wire connects to the CDI and triggers the buzzer or lamp for a overheat.

 

[99yam40]

all of the yams I have played with , had high temp buzzer and RPM reduction to warn the operator there was a problem.
Is this motor remote controlled?
not sure if tiller motors have buzzers or lights if there is no gauges.

when RPM reduction happens or the buzzer or light indicating a problem come on, the operator of the motor is suppose to turn off the motor as soon as they can do that safely to keep from doing major damage to the motor.
it is not OK to keep running the motor

 

[Sea Rider]

Don't know what have been smoking lately, the motor is a Yam 85 ATR. The motor does have an overheat warning device which activates if he temp is too high. The Temp Sensor plays with the CDI and lowers the max wot rpm the motor was revving at to around 2K revs/mim. In this particular case cleaning the TS and its housing curered the rpm reduction issue, the remote control box buzzer was found shot that's why never chimed in.

Happy Boating​

 

[99yam40]

sounds like you think it is OK to keep running a motor that has a problem even after the motor tells you it has a problem.
not a good practice for any kind or type of motor.
stop, find out what that problem is, and fix it before continuing.
if low oil add oil
if overheat let it cool off make sure water pump is pumping water, before running it more.
if needed have it towed and then fixed

 

[Sea Rider]

sounds like you think it is OK to keep running a motor that has a problem even after the motor tells you it has a problem. not a good practice for any kind or type of motor. stop, find out what that problem is, and fix it before continuing. if low oil add oil, if overheat let it cool off make sure water pump is pumping water, before running it more if needed have it towed and then fixed...​

Gee, that sounds like a serious wake-up call to me, relax. In reality was a very stupid issue with Temp Sensor playing tricks on the CDI, easy peasy to diagnose and correct, now the motor runs well as before...

Happy Boating​

 

[Sea Rider]

Update.
Installed a new buzzer on the remote box along a new alum 3 blade OEM 13.5 x 15 prop, went for an open 80 Km water ride with 0 temp issues whatsoever. On our way back the motor caught a large kelp which blocked the lower leg's water intakes, triggered the buzzer alarm and slowed the motor to safe rpm mode, let it cool at idle for 3 minutes till the buzzer went off. The Overheat temp detection and audible warning are working fine as they should, now ready for long open water sunny fun outings.



Was impossible to tell which pitch was the original factory delivered prop on that 85 HP motor as there's nothing stamped on any blade or on the prop body. Will install an induction tach when arrives to check max wot rpm achieved with the new prop and 2-3 souls on board. Forgot to take my GPS to check max speed at full throttle, but didn't felt the combo flying on flat water cond, seems will need to go to a 13.5 x 14 pitch prop ?

Happy Boating
​

 

[Sea Rider]

Yesterday went for a Rib wot ride with the new 15 pitch prop and 3 medium weight boaters. On a flat non windy rowing water course the motor barely achieved a poorly 44.8 Km/H at full hammer down. Although planed the 5.0 Mtr combo fast at 3/4 throttle the top speed was very disappointing to me.

Compared to, my 4.5 Mtr Rib with just a 18 HP motor revving at its max wot rpm range achieved 40 Km/H with 2 up on same water escenario. That Yamy 85 HP motor should fly its own Rib straight to the Moon unless the new 15 prop is exact similar to the previous 15 old prop which isn't known ?

Is there a formula to calculate at which wot rpm is any motor currently revving at without installing a center console or an induction tach to check that out ?

Happy Boating​

 

[QBhoy]

Yesterday went for a Rib wot ride with the new 15 pitch prop and 3 medium weight boaters. On a flat non windy rowing water course the motor barely achieved a poorly 44.8 Km/H at full hammer down. Although planed the 5.0 Mtr combo fast at 3/4 throttle the top speed was very disappointing to me.

Compared to, my 4.5 Mtr Rib with just a 18 HP motor revving at its max wot rpm range achieved 40 Km/H with 2 up on same water escenario. That Yamy 85 HP motor should fly its own Rib straight to the Moon unless the new 15 prop is exact similar to the previous 15 old prop which isn't known ?

Is there a formula to calculate at which wot rpm is any motor currently revving at without installing a center console or an induction tach to check that out ?

Happy Boating​

I suspect you are short on pitch perhaps. Is it a standard Yamaha k series prop you put on her ? How’s the trim set up on her ? I know of similar engines on 16/17ft grp boats that will run a 19” prop no bother. Presumably the same ratio.

 

[Sea Rider]

I suspect you are short on pitch perhaps. Is it a standard Yamaha k series prop you put on her ? How’s the trim set up on her ? I know of similar engines on 16/17ft grp boats that will run a 19” prop no bother. Presumably the same ratio.

It's the same K prop type as the older one, with deck load evenly distributed the combo was running set at neutral trim. With +1 trim the combo achieved barely 0.6 Km/h more than previous max speed achieved. For me a spot on prop maximization will increase the extra top end speed achieved compared to running the combo while with trim up.

The owner had high hopes that running his combo lightly loaded with + trim would provide a much faster top end speed which the GPS highly denied. LOL!!

The issue with this Rib is that the hull is an old design with extremely high hull drag coeficient and a motor blindly propped. Told the owner to hold on, get an induction tach, tach the beast with previous prop to know max wot rpm achieved with 2-3 up which is the usual load and go for way less prop pitches for the motor to run at its max 5500 wot rpm range factory stated.....

Happy Boating​