Different engine RPMs at max throttle

[Dmronan]

Hi this is in regard to a 2020 Yamaha SX210. Has about 5 hours on both port / starboard engines. Just took it out for a spin for the first time in 10 days and noticed at max throttle the port engine was running nearly 8000RPM while the starboard engine was maxing out at only 7500 RPM. The boat had been sitting for 10 days, wet-slipped, but had been idled for 20 min twice in those 10 days. There was also an almost 10mph speed loss (I had ran 48mph the other day, and could only hit 39 today in better conditions).
Wondering if anyone has any explanation or solve for this. Thanks

 

[buckbuck]

I am not familiar with the TR-1 engines but is there an adjustment nut on the throttle linkage? Sounds like something mechanical preventing full movement.

 

[Dmronan]

Yes there is an adjustment nut on each throttle linkage. Nothing noticeably wrong with throttle cables and it seems like all mechanical movement is there. The boat is brand new and throttles worked perfectly last week so it’s just confusing as to why something would happen while just sitting for a week.

 

[tdonoughue]

The difference in speed could be from number of people on board, where they are sitting, growth on the bottom of the boat (I have had some after 2 days wet slipped), more fuel/cargo, wind, current, bimini deployment, debris in the pumps--and I have probably missed several. In fact, debris in the pump could cause it to run more slowly. Might want to check your cleanout port and see if there is something wrapped around the shaft or something.

I was surprised at how much of an effect several of these things can have on top speed. Were your boat older, I would say missing silicone in the pumps, dings on the impellers... Lots of things can throw off speed.

 

[Betik]

My money is on the pump. I hope there is something you can easily see through the clean out

 

[Maineiac]

Did you have the RPM difference before you wet slipped?

 

[Dmronan]

Did not see anything in the pump at all. And @Maineiac, no there was no RPM difference at max throttle before it was wet slipped.

 

[Betik]

You might have to pull the pump. The dent or whatever is there is probably too small to be visible.

 

[Dmronan]

You might have to pull the pump. The dent or whatever is there is probably too small to be visible.

It still just doesn’t make sense to me why something would have dented or damaged the pump in the 10 days that it was wet slipped. Here’s a more detailed description - I am new to jet boats so any further explanation is appreciated. Thanks.

On May 21 it was ran WOT with 45% fuel, one person onboard in choppy conditions - topped out at 48MPH and both engines at 7800 RPM. Sat until May 31st in a wet slip, and when then ran at WOT, starboard engine topping at 7400RPM and port engine still hitting 7800RPM. Boat maxed out at 38-39mph with one person aboard, 40% fuel and calm conditions. It was idled twice in the span of those 10 days. Pulling the boat Sunday to take a better look.

 

[Dmronan]

Just to note, brand new boat with 5 hours on both engines. Only a few weeks old.

 

[Dixie Highway]

Seems like you shouldn't have spark plug issues on a 5 hour engine, but it's easy enough to check those. I lost 3-400 RPM on my TR-1's when the plugs started going bad (at 50 hours).

 

[Matt Phillips]

typically they should be running about the same RPM. The usual culpris to check are both clean out ports feel the shafts, and if you can, reach down to the grates at the bottom of the boat and see if anything is hanging on down there that may be causing a bit of cavitation. In August, we get a lot of milfoil in our marina and it's not uncommon for some pieces to float up under the boat as it's sitting int he slip, then once power is applied, the impellers will suck it through and spit it out the jet stream. Once I'm out in the lake, I always stop, reach down to the base of the inlet, and ALWAYS get more milfoil (I then leave it in the hatch near the top of the tubes to try and keep that crap out of the main part of the lake). While you have your hand in there, reach around the impeller blades and make sure they are smooth and clean as well

The next things to check would be spark plugs, an adjustment on your throttle linkages, and you may also try removing your air boxes and running it with he filters removed (there could be a restriction in there). with so few hours on it, I'd doubt a bad plug, but you NEVER know...it could also be a gapping issue with the plug.

As others have said, fuel, people in the boat (weight), wind and current will all affect speed. There's been several times when out on Tahoe that my speed has varied as much as 5MPH on the same run....all depending on how the wind and waves are hitting. I think the key here is to try and get them to run at the same RPM.

Typically, I don't run at wide open RPM that much as it's pretty expensive to do so (to the tune of 20gph or so). If you can't find the issue, then a trip to the dealer is in order as it's a new boat. You may want to wait on taking it in for JUST that as of now though because once you take it in they won't let it back out until it's fixed. When mine was new, I kept a 1st season "punch list" of warranty items that I took into the dealer in October and basically said look into these, and It doesn't matter how long it takes as she's going into storage for the season. The dealer appreciated that as they were slower and their techs had more time to look at my issues.

 

[Rockfords Fosgate]

I have a similar model. My vote is that the engine that only turns 7500 RPM is overfilled with oil. I don't see 500 RPM differences, but definitely 2-300 when the oil is even slightly overfilled.

 

[BeauSko]

I’m having the same issue with my 2020 AR210. Been like that since day 1 though. I just completed 10 hr service (oil change and filter and spark plugs) and made sure oil was same level for both motors. Port engine actually increased in RPMs to 8000 at WOT (before oil change it was roughly 7800. Starboard engine hangs out at 7700-7800 at WOT. Buckets open exact same distance on both. Throttle linkage look to be adjusted to the same amount of threads showing on each side. I’ll be keeping an eye out on this thread for any other suggestions.

 

[Dixie Highway]

I wouldn’t judge the throttle linkages by thread counts, I had to adjust mine slightly to hit true WOT. What you really need to do is peg the throttles open, then see if you can manually move the TPS wheel farther. As little as 1/16” can make a difference.

 

[BeauSko]

I wouldn’t judge the throttle linkages by thread counts, I had to adjust mine slightly to hit true WOT. What you really need to do is peg the throttles open, then see if you can manually move the TPS wheel farther. As little as 1/16” can make a difference.

Good suggestion...thx!

 

[BeauSko]

So, went right out to the boat and took another look at the throttle position linkage. With the throttle pegged wide open, the throttle body does not quite hit the stop. Hard to see in the pics but here is what it looks like before manually moving the throttle body to the stop and after. Such a tiny difference but could be the culprit.

 

[Dixie Highway]

Hope that does the trick!

 

[Dmronan]

Thanks everyone for the great suggestions. Glad to know I’m not the only one with this problem! Will go test everything first thing in the morning & update with results.

 

[minn19]

My port side throttle cable is off by about a 1/4 inch at WOT. Starboard side hits the stops so they are off by a decent amount RPM wise. This is on a brand new 2020 212S. It’s on my list to adjust before hitting the water this weekend. This has been since day one though.