Trying to find missing WOT RPMs

[yjander]

Do these spark plugs look good? I just put them in April this year. 1.8 liter SHO.

 

[212s]

They look fine...good colour on the insulator indicates proper heat range. Fuel injected engines run a little rich at idle, so normal darkness on threads and surrounding area. More important is to look for wear at the two electrode points - check gap and see if they've worn down. Do not change gap as you may weaken the ground point weld. If gap is too wide, replace them. If not, put them back in or just replace them because they're not expensive. Plugs should last at least 200+ hours unless you run WOT all the time which wears them faster - higher revs means more sparks and wear.

The only reason they recommend checking annually is so they don't get a chance to corrode and stick causing damage to the threads in the head, which is more a salt water environment issue. If you boat in fresh, you can probably inspect yearly and change every 100-200 hours depending on wear rate. I just hit 100 hours and did my oil change and lube this past Sunday after boating. Will be pulling plugs this week to check and I have a new set ready to go in if needed. No hard starting issues so I expect they'll be fine.

 

[yjander]

They look fine...good colour on the insulator indicates proper heat range. Fuel injected engines run a little rich at idle, so normal darkness on threads and surrounding area. More important is to look for wear at the two electrode points - check gap and see if they've worn down. Do not change gap as you may weaken the ground point weld. If gap is too wide, replace them. If not, put them back in or just replace them because they're not expensive. Plugs should last at least 200+ hours unless you run WOT all the time which wears them faster - higher revs means more sparks and wear.

The only reason they recommend checking annually is so they don't get a chance to corrode and stick causing damage to the threads in the head, which is more a salt water environment issue. If you boat in fresh, you can probably inspect yearly and change every 100-200 hours depending on wear rate. I just hit 100 hours and did my oil change and lube this past Sunday after boating. Will be pulling plugs this week to check and I have a new set ready to go in if needed. No hard starting issues so I expect they'll be fine.

Thanks. I just needed someone with more knowledge about plugs than my self to give me some input.

The reason I ask is I’m chasing down extra WOT RPM. I’m only seeing about 6950 or 7000 at WOT. I checked the throttle stop and inspected my pump. Not sure where the extra rpms went.

 

[David Martin]

How many rpm have you lost? My 1.8 turn 7500 in a twin SX240 ho.

 

[yjander]

How many rpm have you lost? My 1.8 turn 7500 in a twin SX240 ho.

It's a SC engine. I think WOT is 7500 to 7700. Today I did a lake test, once I saw 7050 rpm, but most of the time it was 6900 or 6850 rpm. GPS speed at 44.

Set up includes:
SVHO intercooler (upgrade from SHO intercooler)
Lucky 13 pump cone with the largest and smallest spacers
New spark plugs in April 2021
Fresh Oil change in April 2021
I pulled pump, the impeller looked pristine.
Boat has 74.7 hours
Bearings spin nice and smooth
I adjusted the throttle to make sure it was hitting the stop in the engine bay

 

[David Martin]

They do show that engine hitting 7700 and 50mph on review tests but thats one guy on board probably no gear. New to Yamaha nice SC motor. Air box and filter good and clean. How much gear/fuel/top up or head wind that day, and many body's were in boat......... all can effect top end.

 

[yjander]

They do show that engine hitting 7700 and 50mph on review tests but thats one guy on board probably no gear. New to Yamaha nice SC motor. Air box and filter good and clean. How much gear/fuel/top up or head wind that day, and many body's were in boat......... all can effect top end.

So when I first got the boat (January 2020), I was seeing 7500 pretty consistent. The speedometer on the dash was usually right around 49.

Today, just me (240 lbs) and my dog (70 lbs). Bimini was stowed. I had a full tank and I have added a second battery. Other gear included noodles, life jackets, a small magma kettle grill and some dock lines.

I did add Cobra Viper steering this off season, I'm starting to think it might be slowing me down, but none of this should limit the max RPMs, just effect the speed of the boat. I think?

 

[212s]

Check oil level is not too high - too much and the engine is fighting to hit revs. With the 1.8 engines you need to trailer the boat, level the motor and check levels, not on the water.
And double-check the gaps on the plugs - they should be 0.8-0.9". If they're worn in the center the gap will be too big and you'll get a weak spark which will rob you of peak power and revs. Since they're not expensive, do a fresh plugs change and see if that resolves your issue - might have a weak plug, then you'll know what to look for next time. If it doesn't, then you have another issue to find unfortunately.

 

[yjander]

Check oil level is not too high - too much and the engine is fighting to hit revs. With the 1.8 engines you need to trailer the boat, level the motor and check levels, not on the water.
And double-check the gaps on the plugs - they should be 0.8-0.9". If they're worn in the center the gap will be too big and you'll get a weak spark which will rob you of peak power and revs. Since they're not expensive, do a fresh plugs change and see if that resolves your issue - might have a weak plug, then you'll know what to look for next time. If it doesn't, then you have another issue to find unfortunately.

Thanks. I checked the oil today when I got back. It is showing right at the top of the second hole on the dip stick. I will have to wait until later to check the gaps, but when I put the plugs in in April, I gapped them all to .8".

 

[212s]

Thanks. I checked the oil today when I got back. It is showing right at the top of the second hole on the dip stick.

That should be ok but I always fill to half way point in both my cars and boats. It's actually better to be a bit low than high.

I will have to wait until later to check the gaps, but when I put the plugs in in April, I gapped them all to .8".

NGK plugs are pre-gapped and specific for certain engine conditions, and NGK says they should not be adjusted. If you buy new plugs and their gaps are off, exchange them for proper new plugs with the correct gap (I check gaps in the store). Adjusting the gap can damage the electrode weld and cause failure, or even just weaken the weld so the gap changes under combustion pressures. If the gap were to be pushed in to 0.7 that would cause incomplete combustion and rob you of power.

 

[yjander]

That should be ok but I always fill to half way point in both my cars and boats. It's actually better to be a bit low than high.

NGK plugs are pre-gapped and specific for certain engine conditions, and NGK says they should not be adjusted. If you buy new plugs and their gaps are off, exchange them for proper new plugs with the correct gap (I check gaps in the store). Adjusting the gap can damage the electrode weld and cause failure, or even just weaken the weld so the gap changes under combustion pressures. If the gap were to be pushed in to 0.7 that would cause incomplete combustion and rob you of power.

Wow great spark plug information. Thank you! I’ll check them and just buy some new ones.

 

[3 green tornados]

I will lose 500+ rpm at wot if I have oil filled over halfway when leveled on a trailer. My 1.8s are regularly around 8k when I am loaded down surfing.
I bought an oil extractor pump off amazon and it makes oil changes and adjusting oil levels super easy. I bought an OEM Tool’s one that holds 9.5 liters so I can do both motors at the same time.

 

[yjander]

I will lose 500+ rpm at wot if I have oil filled over halfway when leveled on a trailer. My 1.8s are regularly around 8k when I am loaded down surfing.
I bought an oil extractor pump off amazon and it makes oil changes and adjusting oil levels super easy. I bought an OEM Tool’s one that holds 9.5 liters so I can do both motors at the same time.
View attachment 156253

Thanks. I checked filter and it wasn’t wet with oil. I did see some oil in the supercharger pipe but it’s from the PCV system I assume.
I’ll extract all the oil out and see how much comes out. Update when that’s done.

 

[2kwik4u]

How is water flow out of the witness holes on the side of the boat. Wondering if you've slightly clogged an intercooler, not getting good water flow, and subsequently getting hot air in the intake.

Also wonder if it's worth checking the supercharger clutch. Seems to be a rash (2-3) of those go out for others lately. Not sure if that components fails instantly or kinda "wears down" over time. Just a thought.

Could also just be weather related. I thought I had a problem while in the Gulf last month. Only getting ~7,300 rpm from my 1.8L. Didn't want to address it while on vacation, figured I would deal with it later. Got home, and despite being at 800ft elevation instead of sea level I was back to 7,650 rpm. Best I can figure is the Gulf air was 95deg and around 85% humidity, while the air at home was 79deg and about 50% humidity. Those 300revs makes a big difference in speed on my 190.

 

[yjander]

How is water flow out of the witness holes on the side of the boat. Wondering if you've slightly clogged an intercooler, not getting good water flow, and subsequently getting hot air in the intake.

Also wonder if it's worth checking the supercharger clutch. Seems to be a rash (2-3) of those go out for others lately. Not sure if that components fails instantly or kinda "wears down" over time. Just a thought.

Could also just be weather related. I thought I had a problem while in the Gulf last month. Only getting ~7,300 rpm from my 1.8L. Didn't want to address it while on vacation, figured I would deal with it later. Got home, and despite being at 800ft elevation instead of sea level I was back to 7,650 rpm. Best I can figure is the Gulf air was 95deg and around 85% humidity, while the air at home was 79deg and about 50% humidity. Those 300revs makes a big difference in speed on my 190.

Thanks. So the water flow out of the intercooler relief was a little weak at idle, but when throttled up, it was strong. When idling, the intercooler relief was warmer than the lake water and the engine one was pretty hot. not scalding hot, but warm enough that I couldn't leave my hand there for more than a few seconds.

I couldn't feel them when at speed, since I was the only one in the boat.

Water temp yesterday was 84 and air temp was 84 and humidity was 76%

 

[zipper]

Were you getting normal/high rpm's after installing the lucky 13 cone and those spacers. You could be putting more of a load on the pump and motor. Just thinking out loud.

 

[yjander]

Were you getting normal/high rpm's after installing the lucky 13 cone and those spacers. You could be putting more of a load on the pump and motor. Just thinking out loud.

After lucky 13 cone, I was at 7550 to 7600. I even removed one of the spacers before my test run yesterday, but that didn't help. Thought about removing all the spacers and seeing how that runs. I really like the L13 cone, as it don't get any of the cavitation when going WOT from a dead stop or when doing hard turns.

 

[2kwik4u]

After lucky 13 cone, I was at 7550 to 7600. I even removed one of the spacers before my test run yesterday, but that didn't help. Thought about removing all the spacers and seeing how that runs. I really like the L13 cone, as it don't get any of the cavitation when going WOT from a dead stop or when doing hard turns.

Those spacers will tune a couple hundred RPM at most on our boats. We have so much load on these pumps that the spacers really don't change much at all. The effect is much more pronounced in the ski's with the same pumps.

 

[yjander]

Those spacers will tune a couple hundred RPM at most on our boats. We have so much load on these pumps that the spacers really don't change much at all. The effect is much more pronounced in the ski's with the same pumps.

So you're saying that all the spacers removed should still remove cavitation and just run the L13 cone with no spacers? Thanks!

 

[2kwik4u]

So you're saying that all the spacers removed should still remove cavitation and just run the L13 cone with no spacers? Thanks!

It's worth a try to see how it reacts. Swapping spacers is remarkably easy. I wouldn't expect but maybe 2-300rpm change between all spacers and no spacers.