Boat/Engine down on general performance, ideas?

[scubasteve87]

Hey Everyone! Been on the site for a bit now and I'm looking to pick the brains of some other users as I begin to track down an issue that has crept up the past few weeks.

Quick background:
-Boat currently has about 60 hours, 2nd season, completely stock other than a seadek install. Went through 10 hour service last year at the dealer, I winterized the boat and I changed plugs and oil at the start of the season myself (April). Boat has run flawlessly for the first 15 or so hours this season.
-About 3 weeks ago had a rough 2 hour ride back in 3-5 footers after a nice weekend trip. The SX195 handled it much better than expected, albeit averaging only 15-19 MPH for most the trip plowing into some waves. (I boat in bays/coastal waters, Long Island, NY)
-The Following weekend/outing, noticed some immediate cavitation off launch and topping out at 6800 RPMs with top speed only around 35. Pulled over, pulled some seaweed out of the clean-out port and continued on with no issues. Thought it was that simple, but I've noticed I had generally good launches like normal, but could only manage to top out at 45mph around 7100 RPMs.
-Normally with the weight configuration and weather I had that day I can usually touch 50mph comfortably with RPMs around 7500.
-Didn't think too much of it at the time when I first had the issue, but the boat has sounded and felt a little "off" the last few times I have taken it out. By off I mean more cavitation than normal (more so at higher RPM and speed), engine running a little louder than normal (more noise and increase in vibration throughout the boat) and general lack of performance
-Boat still launches well and has the power from the start for the most part and haven't really lost anything on the get up and go. But pushing over 6500 RPMs is where I start noticing the loss of general power compared to last year and earlier this year
-engine feels and sounds a little louder, little "heavier" like it is fighting something that's holding it back. No water issues as all the compartments have been bone dry as usual

Items I have checked:
-Boat is cleaned and detailed after each use in salt water so hull is smooth and clean, no growth or obstructions
-Heat soak likely not an issue as I have good water flow out the cooling lines and the lack of performance has been consistent throughout the day, regarless if the boat just started or has been running for over an hour.
-Intake and tunnel has factory sealant still in place, looks in great shape and no obstructions around the shaft or impeller (I haven't pulled the pump yet, this is only looking from the intake side
-Bucket on pump clears the opening at WOT, no issues there
-Weight in the boat is balanced with minimum weight up front, normally can hit 50-52 with 2 people, gear and full tank of gas
-I have gone through a tank or two of fuel and I have filled up from different locations so I'm thinking I'm ruling out bad fuel as an issue

I want to know what else I should look at to try and track it down. Like I said the boat overall is running fine, starts fine and has solid thrust, but the past few outings have felt "off" and feel its only running at about 90-95% of what it should be. This is what I plan on trying to do this week and upcoming weekend when I have time after work:

-Pulling the jet pump apart and pulling out the impeller and checking the impeller and bearings. Checking the rest of the tunnel to see if there are any other obstructions. Checking the wear ring, etc
-Checking oil levels, spark plugs, caps to the plugs, etc.
-Checking the throttle stop/cable
-Checking the air filter
-General checking of hoses, clamps, etc on the engine to make sure everything is tight.

I'm hoping it ends up being a smoking gun that something above is wrong and I can fix it and test immediately. But I want to cover my bases, so is there anything else specifically I should be looking for? I'm reasonably handy (more carpentry/construction skills as opposed to mechanical) but I'm confident to do a decent amount of work on these boats and engines given how simple their design and operation is so I'll take any suggestions and make a punch list to go through. Thanks for the help everyone!

 

[Matts18]

Sounds like you are on the right track. I had an issue with mine that turned out to be air flow related (my fault), but the engine felt weak throughout the power band.

Have you looked at the stern side of the impeller through the pump with a flashlight? Could be an obstruction.

Throttle stop is an easy check and could explain loss of top rpm.

Is it possible you overfilled the oil and it soaked the air filter?

 

[Julian]

Spark Plugs are where I would start.....

 

[Dean P]

I would definitely pull the pump. Not that hard to do just to make sure there is nothing in there. You may be surprised.

 

[scubasteve87]

Sounds like you are on the right track. I had an issue with mine that turned out to be air flow related (my fault), but the engine felt weak throughout the power band.

Have you looked at the stern side of the impeller through the pump with a flashlight? Could be an obstruction.

Throttle stop is an easy check and could explain loss of top rpm.

Is it possible you overfilled the oil and it soaked the air filter?

As far as I can tell from the stern side pump it looks clear, but I'm sure pulling the pump will give me a better picture.

The oil change went fine and the boat has run perfectly since April up until the last few weeks, so I doubt the filter issue. But I will be looking at it as well to see for sure.

 

[I_squared_r]

As far as I can tell from the stern side pump it looks clear, but I'm sure pulling the pump will give me a better picture.

The oil change went fine and the boat has run perfectly since April up until the last few weeks, so I doubt the filter issue. But I will be looking at it as well to see for sure.

I had oil on my air filter that took 400 RPM off the top. Now I run without an air filter. Where do you boat at? I launch out of either freeport, wantagh, or oyster bay.

 

[Jgorm]

Compression test is a quick verification of engine health. I run them almost anytime i replace the plugs. It's sounds like a water flow /cavitation issue. These are boosted engines correct? A boost leak would cause this too.

 

[scubasteve87]

I had oil on my air filter that took 400 RPM off the top. Now I run without an air filter. Where do you boat at? I launch out of either freeport, wantagh, or oyster bay.

I'm out on the east end. Either launch at Smith's Point for the south shore or out at a local ramp in Riverhead to cruise the Peconic Bay

 

[Cobra Jet Steering LLC]

loud engine noise and loss of top speed may be caused by an exhaust leak inside the engine compartment causing the exhaust to be pulled back into the air intake it will kill top speed if this is happening. and you should notice some hot water inside the engine compartment after it has been running as well.

 

[Bill425]

Hey Everyone! Been on the site for a bit now and I'm looking to pick the brains of some other users as I begin to track down an issue that has crept up the past few weeks.

Quick background:
-Boat currently has about 60 hours, 2nd season, completely stock other than a seadek install. Went through 10 hour service last year at the dealer, I winterized the boat and I changed plugs and oil at the start of the season myself (April). Boat has run flawlessly for the first 15 or so hours this season.
-About 3 weeks ago had a rough 2 hour ride back in 3-5 footers after a nice weekend trip. The SX195 handled it much better than expected, albeit averaging only 15-19 MPH for most the trip plowing into some waves. (I boat in bays/coastal waters, Long Island, NY)
-The Following weekend/outing, noticed some immediate cavitation off launch and topping out at 6800 RPMs with top speed only around 35. Pulled over, pulled some seaweed out of the clean-out port and continued on with no issues. Thought it was that simple, but I've noticed I had generally good launches like normal, but could only manage to top out at 45mph around 7100 RPMs.
-Normally with the weight configuration and weather I had that day I can usually touch 50mph comfortably with RPMs around 7500.
-Didn't think too much of it at the time when I first had the issue, but the boat has sounded and felt a little "off" the last few times I have taken it out. By off I mean more cavitation than normal (more so at higher RPM and speed), engine running a little louder than normal (more noise and increase in vibration throughout the boat) and general lack of performance
-Boat still launches well and has the power from the start for the most part and haven't really lost anything on the get up and go. But pushing over 6500 RPMs is where I start noticing the loss of general power compared to last year and earlier this year
-engine feels and sounds a little louder, little "heavier" like it is fighting something that's holding it back. No water issues as all the compartments have been bone dry as usual

Items I have checked:
-Boat is cleaned and detailed after each use in salt water so hull is smooth and clean, no growth or obstructions
-Heat soak likely not an issue as I have good water flow out the cooling lines and the lack of performance has been consistent throughout the day, regarless if the boat just started or has been running for over an hour.
-Intake and tunnel has factory sealant still in place, looks in great shape and no obstructions around the shaft or impeller (I haven't pulled the pump yet, this is only looking from the intake side
-Bucket on pump clears the opening at WOT, no issues there
-Weight in the boat is balanced with minimum weight up front, normally can hit 50-52 with 2 people, gear and full tank of gas
-I have gone through a tank or two of fuel and I have filled up from different locations so I'm thinking I'm ruling out bad fuel as an issue

I want to know what else I should look at to try and track it down. Like I said the boat overall is running fine, starts fine and has solid thrust, but the past few outings have felt "off" and feel its only running at about 90-95% of what it should be. This is what I plan on trying to do this week and upcoming weekend when I have time after work:

-Pulling the jet pump apart and pulling out the impeller and checking the impeller and bearings. Checking the rest of the tunnel to see if there are any other obstructions. Checking the wear ring, etc
-Checking oil levels, spark plugs, caps to the plugs, etc.
-Checking the throttle stop/cable
-Checking the air filter
-General checking of hoses, clamps, etc on the engine to make sure everything is tight.

I'm hoping it ends up being a smoking gun that something above is wrong and I can fix it and test immediately. But I want to cover my bases, so is there anything else specifically I should be looking for? I'm reasonably handy (more carpentry/construction skills as opposed to mechanical) but I'm confident to do a decent amount of work on these boats and engines given how simple their design and operation is so I'll take any suggestions and make a punch list to go through. Thanks for the help everyone!

I had the same symptoms on one engine in the 2016 chaparral and it end up after I had the certified brp rotax mechanic out to be low on oil causing it to go into limp mode.

 

[Cobra Jet Steering LLC]

I had a sea doom 4 stroke that did exactly what his boat is doing and it ended up being an exhaust leak, It took me months to find the cause and the symptoms were exactly the same, it ran good just not hitting top speed by about 10 m p h limp mode on the other hand is sub planning speed.

 

[Gym]

Before you pull the pump I would check the clearance between each impeller blade and the liner. Thinking one blade may have a slight bend in it due to impact. Are there any rub mark's on your liner indicating a possible impact to an impeller blade?

 

[scubasteve87]

Thanks for the recommendations. Haven't had any water in the engine compartment during the runs. As far as I can see into the intake the impeller blades look good. No Nick's, marks, discoloration. No rubs or scratches on the tunnel either.

I plan on pulling the pump and check out things that everyone has suggested at the end of the week. I'm jammed with work and family stuff this week so the weekend is likely my first crack of running through the list. Much appreciated for the comments!

 

[scubasteve87]

So phase 1 of the checklist was completed. I pulled the spark plugs (look in good shape) and reinstalled to make sure good connections everywhere. Oil level is good, no over fill. Air filter looks clean during my inspection as well.

Finally I pulled the jet pump and impeller and everything looks great. No dents, bends, chips in the impeller (photos attached). The tunnel looked decent with all the sealant still in place. The wear ring and rest of the tunnel is smooth. The dark spot on the bottom I think may have been from sitting water as I had that pretty much through the rest of the pump all the way to the gate.

It didn't look or feel like a burn, but perhaps someone with more experience or knowledge chime in. I'm hoping to get back on the water this upcoming weekend for testing to see if anything has changed.

Any other ideas or places to check? At this point I have ordered new plugs as it's an easy swap.

 

[Bill425]

Are you getting anything from diagnostic codes?

 

[scubasteve87]

Are you getting anything from diagnostic codes?

No codes thrown or anything. I haven't hooked up anything to the ECU like yes or anything. Felt more mechanical like something was physically slowing it down. I'll be swapping plugs and getting it out the water this weekend and will if any changes or new symptoms to pin down.