10 hour oil change speed decrease

[Seadeals]

Focus on the rpm. Add the missing rpm, the speed follows.

FWIW in about 250 hours of running my boat in all kinds of conditions, I can’t think of anything changing my max rpm (Bimini up/down, full cooler/no cooler, 2 people/6 people, windshield open/closed, fresh wax/no wax) other than when I swapped out a tach that read about 500 high for a more accurate one. YDS has always confirmed max rpm right around the ECM-controlled 8000 rpm. Speed is slightly affected but my max of 43 has never been below 38 in the worst of any of those relative conditions.

RPM is about fuel, spark and air. Plugs, filters, fuel or a pump issue (debris/impeller damage or pitch mod/cavitation) are the only culprits I feel affect it. I only run ethanol-free 87 or 91 and use sea foam in every tank to keep things clean and reduce my chances for moisture buildup in the fuel. It could be possible you got bad gas; but seems like it would give you trouble at idle. Ringfree, Stabil, Seafoam, etc cAn only help and seems worth the simple $ to help troubleshoot out the gas.

On the air filters, I recommend just removing one and comparing the two engines in exactly the same conditions at the same time. If they are still both low you know it is not the filters and you don’t have to mess with the other engine.

 

[HangOutdoors]

@Seadeals That is how I have been thinking about it. My RPM's are low on both engines. Of course other factors may bring the speed down, conditions, weight etc. But the RPM's should be up there. That is why I am bothered.

 

[HangOutdoors]

Which sea foam do you use and what size/mixture for 50 gallons. Looks like it could get pricey over the long haul.

 

[Gunner]

Yamaha ring free is pretty cheap to run, one ounce per 10 gallons, cheap insurance

 

[HangOutdoors]

I have two bottles of that was planning on using it in the next full tank. I have about 18 gallons left right now.

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[Seadeals]

Ringfree is best but more expensive. If you have it, use it. Yamaha says to. I use Seafoam because I am cheap and believe it does most of the same things. Auto stores are a rip unless a good sale. It can be found for under $7 a can. I use 2 for 50 gallons but seldom run dry, so usually 1. I just use the garbage in=garbage out logic. Good fuel is a way to avoid more costly problems.

 

[Rockfords Fosgate]

Focus on the rpm. Add the missing rpm, the speed follows.

FWIW in about 250 hours of running my boat in all kinds of conditions, I can’t think of anything changing my max rpm (Bimini up/down, full cooler/no cooler, 2 people/6 people, windshield open/closed, fresh wax/no wax) other than when I swapped out a tach that read about 500 high for a more accurate one. YDS has always confirmed max rpm right around the ECM-controlled 8000 rpm. Speed is slightly affected but my max of 43 has never been below 38 in the worst of any of those relative conditions.

I had 9 on the boat last weekend, and was capped out at 34-35. The extra weight definitely impacts my top end, especially with moderate chop and boat wake. The boat/engines just never have enough time to regain the momentum and inertia.

 

[HangOutdoors]

@Rockfords Fosgate Did you happen to glance at Max Steady RPM's at WOT? I get the speed will come down as I load it up, and I am ok with that. More or less looking for the missing RPM's that I have.

 

[Rockfords Fosgate]

@Rockfords Fosgate Did you happen to glance at Max Steady RPM's at WOT? I get the speed will come down as I load it up, and I am ok with that. More or less looking for the missing RPM's that I have.

Nope, but I will tomorrow. Another outing with 9!

 

[isitsummeryet]

I plan on testing on Sunday morning hopefully. I am going to double check and redo the following for testing purposes. Looking for the 500 RPM's or so that I am not getting.

1) Don't eat any food the day before or in the morning to bring the weight down.
2) Just myself and the Admiral.
3) Full tank of Gas, no additives. 87 Octane from Mobil Gas Station.
4) Already reviewed and adjusted the throttle linkage just a bit in the engine compartment on one side, there was just a hair of slop.
5) Make sure everything is removed that wasn't in the boat on pre 10 hour oil change testing.
6) Bimini Top Down
7) Will Draw down oil till just above the "L" hash mark Cold. It is half way now.
8) Will also bring 2 quarts of oil to check and add if needed when hot to make sure.
9) Top of boat above water line has been waxed and shined. Bottom of boat below waterline has been cleaned, no wax.
10) Spark plugs, the new set, have been removed again and all Gap's have been checked and Verified.
11) Will hopefully get similiar water conditions, albeit about 6-10 degrees warmer with low to no wind if possible, light chop. (Same as original test)
12) Double checked alignment of Jets.
13) Will test with both air filters in and then with air filters out to see if it makes a difference. Although I don't see oil in them I will verify.
14) All plugs will be in and I have lifted the tongue up high to verify I am not carrying around a bunch of water.
15) Oil change and filters were all from the Yamalube Kit from dealer.

So this is the plan. If anyone has any further suggestions let me know. Don't get me wrong, it has plenty of punch and pulling power, it is just the top end has come down and the RPM's that I originally hit at 2.5-3hours were 500 RPM's higher.

Will definitely post my results and shoot a pic of speedo and RPM gauges.

Goal is 7600-7800 RPM's and Circa 43 mph on Speedo, which is where it was at. I will GPS verify as well.

If the results are less then optimal, it will go to the dealership.

In the end I want to verify that I didn't mess something up, and that my boat is running at what is should be. Of course it is what it is if everything is Ok.

As an FYI, all the lakes around here have a 40 mph speed limit and unless you get lucky in Lake St. Clair you aren't running WOT because the chop will beat you to hell as well as your boat.

Try not to eat starting a couple days prior and also try to be as dehydrated as possible to cut down weight! Don't wear any clothes as well..

Sorry couldn't help myself with that first point of yours

 

[HangOutdoors]

Just went out and releveled the boat and double checked that the oil was just above Low now. I pulled out a bit the other day since it was half way.

 

[Gunner]

I agree I would think regardless of the conditions or weight on boat you should still hit max rpm, seems all those variables would only effect top speed, but I'm no engineer.

 

[Gym]

As I suggested before pull both air filters out. See if your RPM & speed improve.

 

[HangOutdoors]

@gymThat is the plan Sunday Morning

 

[ZGhost]

Just went out and releveled the boat and double checked that the oil was just above Low now. I pulled out a bit the other day since it was half way.

For correct oil level check, it should always be checked while the boat is on the water not the trailer.

 

[HangOutdoors]

@ZGhost I have read it both ways on forums here. The manual indicates either way. If there is a specific reason and it is better I am all for it. I leveled off the engine with my level and blocked the tires. I wanted to make sure that it was low enough. Ran it on the hose for 6 minutes before checking. I will reverify on the water on Sunday after I idle out of the bay into the lake which should warm the engines again. I will be carrying oil to add if needed. I just didn't want to have to pull any out while on the water.

Yamaha Manual 2020 AR210

 

[Inthrustwetrust]

@Seadeals That is how I have been thinking about it. My RPM's are low on both engines. Of course other factors may bring the speed down, conditions, weight etc. But the RPM's should be up there. That is why I am bothered.

Was there significant air temp and humidity changes from your pre 10 hr to post 10hr? IE your first 10 hours were in the spring in 60s and 70s and dry air, and now it’s summer time with 90s and high humidity?

As it gets hotter and more humid the density altitude climbs, so even though your lake might physically be at 1000ft above sea level, the characteristics of the atmosphere around you are actually several thousand feet higher, leading to a performance decrease in the motor.

My knowledge of this is mainly from turbine aircraft, you can easily see a 5-10%+ decrease in power/rpm in the summer, but those engines are spinning at 40,000rpm, compressing and exploding shit tons of air, not sure if that’s a fair comparison to a piston engine.
I know drag cars and nascar motors produce less power when it’s hot out. I’m not really sure how much this would effect a small boat motor.

Might be a factor, might be some useless knowledge from me.

 

[ZGhost]

@ZGhost I have read it both ways on forums here. The manual indicates either way. If there is a specific reason and it is better I am all for it. I leveled off the engine with my level and blocked the tires. I wanted to make sure that it was low enough. Ran it on the hose for 6 minutes before checking. I will reverify on the water on Sunday after I idle out of the bay into the lake which should warm the engines again. I will be carrying oil to add if needed. I just didn't want to have to pull any out while on the water.

Yamaha Manual 2020 AR210

The reason is simple, your engine needs oil to operate, the engine operates while the boat is on water, not on trailer. So where do you think the oil level is more important? You can choose whatever method you like.

 

[minn19]

Just went out and releveled the boat and double checked that the oil was just above Low now. I pulled out a bit the other day since it was half way.

Personally, I would be very nervous running the engines with minimal oil like that. I’m guessing that isn’t the issue either as they should have been designed to run full RPM at the full oil level. Good luck and I would be frustrated to, but just be careful you don’t cause yourself a much bigger headache chasing those lost RPMs.

 

[HangOutdoors]

Why would you be nervous as long as the oil within proper parameters?

@ZGhost That makes sense, but depending how you are loaded in the boat on the water in may list to one side or forward or aft. Level the engine and that is where it should be. Just spoke with the dealer service department, since I need to pick up a part, they level the engines with a level, since they don't put them in the water to change oil on 10 hour, 100 hour or any oil change service. He also recommended that is just above the L on Warm.