New Boater with Jetboat questions!

[jmboater]

Hello everyone!

I purchased a new-to-me 2006 Yahama AR210 this year for my family to enjoy on the water. I'm experiencing some lack of performance and wanted to understand some more seasoned opinions on if I am dealing with cavitation, engine issues, or something else entirely.

Low weight runs: While the boat is in use with a few people, it gets up to plane quickly and easily, pulls a tuber, and has a top speed of 30ish. Engines rev out differently.. Port engine revs to 8400 and starboard at 7100.

Capacity runs: When you get the boat to 8 or 9 individuals, it takes a long time to hit plane. Sometimes it can't even get there and we max out around 23-24 according to the onboard speedometer.

The previous owner hinted at not messing with the clean out ports very often (should have been a red flag had I known better) and when I finally got them unstuck, I did find pond weeds wrapped around the shaft. I was able to pull all of that out but it seemed the boat was run like that often. There was also reference to the cooling system flush being used for winterization only to make it easier. I have since read the owners manual and understand differently.

Where should I start? I'm not the most mechanically savvy but am a DIYer for everything non-mechanical. I'd probably not trust myself to check spark plug gaps but wouldn't have an issue pulling the impeller.

Does this sound like the impeller and wear ring could cause the issues I am seeing?

 

[Dave burke]

Pretty sure your boat has the smaller TR1 engines but even at that, the top speed seems quite low. And a 1300 difference in RPM is troubling. Did you ask the previous owner about maintenance and/or do a sea trial? If so, has something changed?

if I were you I’d start with the engines and throttle cables (that could explain the difference in RPM). Has the oil and filters been recently? If not, do this. Change the plugs too. If you’re going to change the plugs, I’d do a compression test at the same time. Buy or borrow a compression gauge if you don’t have one. Some auto parts store will lend you one.

if you still have a difference in RPM, check the throttle linkages at the engine and see if you can adjust them if they look different.

Once you’ve done this troubleshooting, maybe pull the pumps and check the impellers and wear rings. I’d check for symptoms by searching on this forum first. I know one of the symptoms is cavitation. Personally, I’ve not had this problem (yet!) so I’d see what others are saying about damage to the impeller or wear rings.

 

[jmboater]

Pretty sure your boat has the smaller TR1 engines but even at that, the top speed seems quite low. And a 1300 difference in RPM is troubling. Did you ask the previous owner about maintenance and/or do a sea trial? If so, has something changed?

if I were you I’d start with the engines and throttle cables (that could explain the difference in RPM). Has the oil and filters been recently? If not, do this. Change the plugs too. If you’re going to change the plugs, I’d do a compression test at the same time. Buy or borrow a compression gauge if you don’t have one. Some auto parts store will lend you one.

if you still have a difference in RPM, check the throttle linkages at the engine and see if you can adjust them if they look different.

Once you’ve done this troubleshooting, maybe pull the pumps and check the impellers and wear rings. I’d check for symptoms by searching on this forum first. I know one of the symptoms is cavitation. Personally, I’ve not had this problem (yet!) so I’d see what others are saying about damage to the impeller or wear rings.

Thanks for the response, Dave.

The previous owner did provide maintenance records (winterization and oil change annually by the local marina). During the sea trial, things seemed normal but it did present with the rpm differences (I chalk this up to first time owner/buyer). I don't believe anything has changed since purchase, but we only took the boat out under load (capacity w/ people, coolers, etc) after purchase and noticed the extent of the performance loss.

Perhaps I'll buy my neighbor a bottle of scotch and see if he can walk me through the spark plug change and compression tests.

For the throttle cables, it is direct wire to an electronic throttle body from what I can tell. It does not seem that the throttle cable adjustment is needed (both seem to be aligned and hitting the stops where they should) from an untrained eye anyway.

- Jon

For the throttle

 

[jmboater]

I believe the engines are the MR1, not TR1 though.

 

[lazergeek]

What altitude are you at?
Assuming the lower RPM's is not altitude related I would start by replacing spark plugs an check for overfilled oil on the starboard motor could be the cause of the Lower RPM's, the oiil needs to be below the top line.

If your at a higher altitude then your port motor may need an impeller and or wear ring.

 

[Dave burke]

Thanks for the response, Dave.

The previous owner did provide maintenance records (winterization and oil change annually by the local marina). During the sea trial, things seemed normal but it did present with the rpm differences (I chalk this up to first time owner/buyer). I don't believe anything has changed since purchase, but we only took the boat out under load (capacity w/ people, coolers, etc) after purchase and noticed the extent of the performance loss.

Perhaps I'll buy my neighbor a bottle of scotch and see if he can walk me through the spark plug change and compression tests.

For the throttle cables, it is direct wire to an electronic throttle body from what I can tell. It does not seem that the throttle cable adjustment is needed (both seem to be aligned and hitting the stops where they should) from an untrained eye anyway.

- Jon

For the throttle

Re the the throttle cable, the key is if it’s hitting the stops like you say. FYI, I think it’s unlikely that it’s an electronic system, unless the previous owner changed it. Mine is a 2017 and it’s mechanical.

Sounds like a good plan to buy your neighbor a bottle of scotch. Be cheaper than buying a compression gauge!

Re the oil, probably ok not to change if it was done by the local marina but check the level as @lazergeek suggests.

 

[zipper]

Change the spark plugs. That may help with the difference in rpm’s. 8 or 9 people at 150# rated, is a lot of weight after figuring in gear and fuel.

 

[Acard7]

I believe the engines are the MR1, not TR1 though.

Post a pic of the engines, then we will know for sure if it’s the MR1s!

 

[buckbuck]

2006 has the lower output MR-1. It is a good engine. I would change the spark plugs and get underneith and look at the shaft and impeller. This is probably an 'easy to resolve' issue.

 

[jmboater]

What altitude are you at?
Assuming the lower RPM's is not altitude related I would start by replacing spark plugs an check for overfilled oil on the starboard motor could be the cause of the Lower RPM's, the oiil needs to be below the top line.

If your at a higher altitude then your port motor may need an impeller and or wear ring.

Chicagoland.. not likely high altitude related. Note taken on oil overfill.