Significant Speed Loss

[ThirdRay]

I just picked up a new to me 2020 SX210. Took it out yesterday and everything seems great….except the top speed is significantly lower than expected. With just my wife and I on board, we could only hit 30 mph at around 7800 rpm. We mostly cruised around at 24 mph and 6200 rpm, but the lack of top end speed has me looking for a cause. Searching this forum, cavitation is a worry but not sure if it’s the cause or something else. The boat ride was smooth, we hit plane easily and I didn’t hear any rattle can noises.

I’m not entirely new to jet boats, we had a sea doo speedster when I was a kid and a sea doo challenger a little later. I’ve had my boaters license since I was 11 so I’m familiar with how they handle. For my boat, the hull was cleaned before I put her in, I inspected the clean out, intake grate and what I could see of the impeller. I did notice the starboard clean out plug seems to have a seal issue and isn’t sitting right. I pulled it when we stopped for lunch and water was filling the hole.

Looking for advice on where to start - oil was changed by the dealer I bought it from and the level looks good. I haven’t checked the spark plugs or the air filter. I don’t want to go back to the dealer since it’s a 5 hour round trip, but if this is a major issue I suppose I will have to. Previous owner wet slipped in a fresh water lake. There seemed to be some gunk on the jets when I got it but I got most of it off.

 

[FSH 210 Sport]

Location?
Altitude?
Fuel load?

 

[ThirdRay]

Started with 75% fuel, got down to 15 and the top speed was the same. Sea level in the Chesapeake bay.

 

[Babin Farms]

It was good before the oil change and this happened after an oil change?

 

[ThirdRay]

It was good before the oil change and this happened after an oil change?

First time I’ve taken it out, so I don’t have a comparison before the oil change.

 

[FSH 210 Sport]

I did this thread a short time ago.

Thread 'TR-1 Proper Oil Level to avoid RPM loss'

May 18, 2025

I’ve seen a lot of posts about the TR-1 oil level, and been part of a few of them. I’ve seen the claims that high oil levels reduce peak rpm’s in this engine. I’ve also seen at least one video that gave bad information about how to check the oil level which led me to believe that this could be the cause for rpm losses, but I never could figure out the mechanism for the rpm loss until yesterday when I was replying to a thread for @CarolinaJet and excessively high oil levels while out on the water. Then things became clear to me as I remembered another post where a guy had pulled...

• FSH 210 Sport
• Replies: 18
• Forum: General Discussion

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Start there to make sure you’ve got the oil level correct, this is a common problem.

You’re pretty close on max rpm’s, I’m assuming you have TR-1 engines, they are rated at 8000 rpm.

Next, did you just use the OEM speedometer? That’s a water wheel and it could be fouled and not spinning freely. Try using a gps based speedometer or use a cellular based speed check to make sure of what your top speed is.

Use a strong light and look at the impellers, they should not have any dings or deformities on the leading edges. The gap between the blades and the wear ring should be between .014-.0177”

 

[ThirdRay]

I did this thread a short time ago.

Thread 'TR-1 Proper Oil Level to avoid RPM loss'

May 18, 2025

I’ve seen a lot of posts about the TR-1 oil level, and been part of a few of them. I’ve seen the claims that high oil levels reduce peak rpm’s in this engine. I’ve also seen at least one video that gave bad information about how to check the oil level which led me to believe that this could be the cause for rpm losses, but I never could figure out the mechanism for the rpm loss until yesterday when I was replying to a thread for @CarolinaJet and excessively high oil levels while out on the water. Then things became clear to me as I remembered another post where a guy had pulled...

• FSH 210 Sport
• Replies: 18
• Forum: General Discussion

• 
• 
• 

Start there to make sure you’ve got the oil level correct, this is a common problem.

You’re pretty close on max rpm’s, I’m assuming you have TR-1 engines, they are rated at 8000 rpm.

Next, did you just use the OEM speedometer? That’s a water wheel and it could be fouled and not spinning freely. Try using a gps based speedometer or use a cellular based speed check to make sure of what your top speed is.

Use a strong light and look at the impellers, they should not have any dings or deformities on the leading edges. The gap between the blades and the wear ring should be between .014-.0177”

Correct, TR-1, 140 hours on each. I had my phone running Argo but I don’t recall looking at the speed to compare, thanks for the tip. I was on the OEM speedo. Appreciate the help.

 

[FSH 210 Sport]

Correct, TR-1, 140 hours on each. I had my phone running Argo but I don’t recall looking at the speed to compare, thanks for the tip. I was on the OEM speedo. Appreciate the help.

Too high of oil levels have been reported to lower rpm’s by 500 or so, I don’t think that’s your issue but be sure they’re not over filled.

If you find that the oil levels are correct you could try pulling the air filter elements and see if you pick up any rpm’s. Make sure the air boxes are super clean before running the engines without air fikters. I replaced mine with Rivas and picked up roughly 200 rpm but I’m at 5000’ ….

I’m not sure how fast your boat should go, I think our boats are roughly the same weight empty, mine will do around 41 mph at 650’ above sea level on the water wheel. I’ve seen where some guys have recorded 45 mph on the ocean but probably didn’t have as much stuff in their boats as I do.

 

[ThirdRay]

Too high of oil levels have been reported to lower rpm’s by 500 or so, I don’t think that’s your issue but be sure they’re not over filled.

If you find that the oil levels are correct you could try pulling the air filter elements and see if you pick up any rpm’s. Make sure the air boxes are super clean before running the engines without air fikters. I replaced mine with Rivas and picked up roughly 200 rpm but I’m at 5000’ ….

I’m not sure how fast your boat should go, I think our boats are roughly the same weight empty, mine will do around 41 mph at 650’ above sea level on the water wheel. I’ve seen where some guys have recorded 45 mph on the ocean but probably didn’t have as much stuff in their boats as I do.

It’s supposed to be 40-45 mph, so losing 25% felt pretty significant. I’m doing the spark plugs and air filter this week, just ordered the parts. Repair kit for the clean out plug as well, figured it couldn’t hurt. I’ll report back after all that and the oil level check in case this thread helps anyone out.

 

[FSH 210 Sport]

Those are prudent moves…. But don’t replace the air filters unless you verify that they are indeed bad…. Save the money for some RIVA K&N style air filters as they do make a difference.

The rebuild kits for the clean out plugs is good as well, be sure and clean the area’s where the seals ride. If the seals are really bad you could have had cavitation when accelerating, did the engines feel like there was a slipping clutch and then it grabbed and the boat accelerated? Another indication is that the tachs shot right up to 8000 rpm then came back down.

Be sure and check the water wheel closely from the bottom of the boat for fishing line or something else wrapped around it, then re check the water wheel speed against a gps or cell speed tester.

As I said earlier, your rpms are quire close to the 8000 max. The TR-1’s are sensitive to higher density altitudes.. so warm humid days will bring the rpms down a bit. Your7 speed issue is not related to the rpms of the engines, at 7800 on my fsh I’d be doing somewhere around 37-38 mph or perhaps a tad higher.. so it could be one of the following;

Excessive gap between the impeller and the wear ring, the gap should be between .014” and .0177”.
Weight in the boat
A dirty hull
Wind
Misaligned pumps-unlikely but possible

 

[Babin Farms]

It is normal for the cleanout to have water on the top. When you pull the plug out while in the water, the water level will equalize out to how deep your vessel is in the water. If you stop suddenly water will wash up on the swim platform getting water in that area as well.

 

[Neutron]

Getting almost 100% rpms has me thinking its not engine related,
Look closely to the impellers and intakes. Lack of speed with good rpms is something else.
Is the hull painted with bottem paint, clean and smooth?

 

[drewkaree]

Other conditions you didn't report - weather? Windy, temps? Water condition - were you in much chop? Bimini up? Your boat should be similar to mine, and at least 40 should be easy in decent conditions. Oil level can drop you quite a bit, depending on the rest of the conditions. I've got a high score of 53 on mine, cool fall temps, bimini off, glass calm - perfect conditions that I never run in, nor do I concern myself with that speed. 35-40 is consistent for me, with 35 being in some chop and just me and the wife. I could hit 30 in 2' swells, but it wasn't comfortable, and I was concerned with how it was beating up the wife. Something is amiss, but there's some info somewhere that may point us to issues. That big a drop, I'm thinking Neutron is onto something. That's a LOT of speed being scrubbed off at those revs for some reason.

 

[tdonoughue]

Agree with @Neutron as well. I was noting that one of the plugs is not seating properly? That would be where I would start. If you don't have a good seal there, that could do it between cavitation and pressure leakage...

 

[ThirdRay]

Ok updating this since I’ve had time to tinker and take the boat out.

First, oil level was overfilled, took enough out to get below the fill line when warmed up. Air filters had oil on both sides, so changed those out (paper for now, I’ll upgrade later). Spark plugs were worn but the wear showed normal engine performance, nothing concerning there but I replaced them all anyway. That got me 5 mph back. Speedo was also off, checked it against Argo.

In trying to get the rest of the speed, I looked over the hull. Bottom of the boat sediment buildup on it. I thought it was just dirt but it’s caked on really good and thick, almost like cement but it does eventually come off after power washing the hull half to death. Did some of that today and got a good amount off, especially around the intake but there’s more to do there. Any suggests for a hull cleaner on what seems like mineral deposits? This was docked in a freshwater lake most of the time before I bought it.

 

[drewkaree]

Ok updating this since I’ve had time to tinker and take the boat out.

First, oil level was overfilled, took enough out to get below the fill line when warmed up. Air filters had oil on both sides, so changed those out (paper for now, I’ll upgrade later). Spark plugs were worn but the wear showed normal engine performance, nothing concerning there but I replaced them all anyway. That got me 5 mph back. Speedo was also off, checked it against Argo.

In trying to get the rest of the speed, I looked over the hull. Bottom of the boat sediment buildup on it. I thought it was just dirt but it’s caked on really good and thick, almost like cement but it does eventually come off after power washing the hull half to death. Did some of that today and got a good amount off, especially around the intake but there’s more to do there. Any suggests for a hull cleaner on what seems like mineral deposits? This was docked in a freshwater lake most of the time before I bought it.

 

[FSH 210 Sport]

View attachment 236238

I can attest this stuff works well and pretty quickly. This concoction is no joke, keeps kids, pets and unsuspecting humans away. Start upwind and work your way down wind.

I would add that one needs to wear; safety glasses, long sleeves, long pants, closed toed shoes, cloth hat, nitrile or playtext gloves. When you’re done remove the clothes and take a shower. Wash the clothes separately.

 

[drewkaree]

From the sounds of it, you could probably eliminate the water, and just go 50/50 with the Zep & acid, but start with that ratio, and see how it works.

If that DOESN'T work, I dunno what your options are, but I expect that mix will prove to be fruitful. I'd be leery with the pressure washer, if it needs that much effort. I'd be worried about going too deep and not realizing it , and effing up the gelcoat