Thrust issues

[mbalogh]

Hey everyone,

I know, just another thread about low thrust. Sorry! I’m new.

I’ve been boating for close to 30 years but I just bought my first jet boat, a 2007 Yamaha AR 230. So I’m busy learning everything I can about it. It is a decidedly different animal than any of my previous boats.

We dropped it in the lake today for the first time, and had very little thrust out of either engine coming out of the hole. I was able to get it on plane after plowing through the water for some time and then it seemed to act normally. The level of thrust seemed fine. I thought maybe I just had some air in the pumps from dropping it in the water, but after I came off plane it did the same thing trying to get back on plane.

I’ve done a bunch of research and I know the common problems, leaking manhole covers, the silicone seal on the plates, something being stuck in the pumps, the sleeves around the impeller‘s being worn, or damaged impellers. I’ve checked all of this and as far as I can tell none of these issues exist. The seals on the manhole covers are brand new, I just replaced them, and don’t seem to have any play. And the impeller sleeves were replaced last summer by the previous owner. The impeller‘s seem to be in generally good condition with exception exception of one small nick on one of them. The silicone looks fairly fresh and there are no visible separations I can see on the surface.

So my question is this… What should I be looking for on some of these issues and how do I narrow this down? Yamaha mechanics are apparently few and far between in my part of the world and at this time of year I’m gonna be waiting weeks if I try to get it fixed by a mechanic, so I’m hoping to find the issue on my own. Thanks for any advice!

 

[Acard7]

How are you getting on plane? I’m usually around 7-8k RPMs to get it on plane quickly. And stick around 7-8k for 30ish mph. It’s been so long since I have been on my boat sadly 🥲

You could’ve had some cavitation as well so definitely make sure those pumps are clear.

 

[gt5pilot]

2008 ar230 here and agree with the numbers just stated.

I don't believe that I have ever just throttled down with the boat at rest so I can't speak to cavitation issues related to that. I generally rev to 4000 for a second or so before rolling into the throttles. It comes up on plane quickly without hesitation and I spend most of my running at 7400 or so @ 26-30 mph depending on lake conditions.

Rarely have less than 4 people on the boat and sometimes 8, doesn't really make much of a difference in performance.

By myself with a full tank of gas mid 40s is pretty easy.

What RPM range and speeds do you see?

 

[Babin Farms]

Agree with the two posts above. Need more RPM's to get it going. These engines spin over 10k at WOT and to hop up on plane you need to get well over 8k and then back it down to the desired speed/RPM once your up and going.

 

[mbalogh]

Thanks for the responses. I was running at about 8k rpm to get on plane with 1/4 tank of gas and only me and my son on the boat. It was getting on plane eventually, but took a good 45-60 seconds to get there. I’m definitely not just hammering down to full throttle and causing cavitation. The port engine was definitely cavitating a bit if I pushed it, but not starboard. Checked the pumps and as far as I can tell they’re clear.

 

[Babin Farms]

Is the hull of your boat clean? If it feels rough to the touch that will also drag you down. My recommendation is to hammer down, see what it'll do and get used to the difference between prop and jet drive.
If you have any cavitation it will affect getting up on plane. Usually it'll feel like the boat is vibrating, sometimes really bad like you lost a blade on a propeller.

 

[Scottintexas]

where are you at ?

have your crawled under the boat and looked at the impeller through the intake ?? what do they look like ?

air getting trapped in the pump by unloading the boat is NEVER an issue,

what do your cleanout plugs look like? are they easy to install /remove ?


.

 

[mbalogh]

Impellers look good except one small ding on the starboard side. Very minor. I just put new OEM seals on the clean out plugs, they come in and out with ease and have no play or wiggle when locked. Is it possible to suck air through the clean out plugs? Or would water shoot out if they were leaking? They were dry in the holes after I ran the boat for about 20 min. That’s the only thing I changed with respect to the pumps since the previous owner. He’s a friend and says it worked perfect last summer.

I know jets and props are different but I’ve been on plenty of Yamaha and other jet boats and none behaved like this. It’s simply not right. If I had my whole family on the boat I don’t think it’s ever get on plane.

 

[Scottintexas]

from a complete stop you should be able to put the throttles full forward immediately, it may take a second or two to "hook up" but after that you should be firmly planted in the seat until 45mph,

Do you know if the impellers are in the correct sides, each impeller has a specific pitch

has the boat ever been able to do this for you ?

seeing as the previous owner replaced the wear rings "impeller sleeves" last year I would probably start there by measuring the gap between the impeller and the sleeve,

I'd pull the impeller and shaft just to make sure they are on the correct side (the impeller will have a part # on it), it will also give you the opportunity to check your sealant, not only is it there but by gently pulling on it to make sure it's still adhered to the hull

update your profile so we know where you are at,

 

[Babin Farms]

If I just go about 8k RPM it will take my boat forever to get on plane. Try higher RPM's and see what it'll do. It takes some getting used to the MR1 and the way it makes power compared to other engines.

 

[mbalogh]

Appreciate all the feedback everyone! I just brought it to the ramp with a friend of mine who knows jets a little better than me and tested it on the trailer a bit (because that’s all we had time for) but it seemed to him like it’s all good. I know from experience a trailer test isn’t real world, so I’m gonna dump it back in again this week when I have time and play with it. Hopefully it was a fluke, maybe I had something in a jet that came out when I pulled the boat. I dunno, fingers crossed. But I will definitely let you guys know. Again, thank you!

Just for sanity sake, is there a write up anywhere on all the spots you should check the silicone sealant? I see a few spots where I had to check and they look good but don’t know if I hit all of them.

 

[mbalogh]

So I was able to piece together where I had to check the silicone sealant from several threads. Turns out more than half of mine was missing. Scraping it out worked quite well with a half-inch wood chisel that was nicely sharpened, and I would have been able to get the job done in maybe two hours. Unfortunately, two of the bolts holding the intake grates to the ride plates stripped and I had to drill and tap them, which took me a good part of the day. Otherwise not such a bad job. And it worked! No more cavitation.

Unfortunately, after putting the boat in the water today and tying up at the slip I discovered that the seal around the starboard driveshaft was leaking and I had to pull the boat again. On to more research about how to replace the drive shaft bearing, because mechanics around here are 6 weeks out on getting to it. *sigh*

Thanks to all those who took the time and gave advice!!

 

[Acard7]

Please elaborate (with pics) where the water was coming from? It could be your intermediate bearing and if you have some help it’s actually very easy to change!! There are couple threads on how to do so on here already!

 

[mbalogh]

Thanks! Appreciate the advice. Give this link a try, should be a video of the water coming in. It’s behind and below the starboard motor to the left of the bilge pump.

20220612_204754000_iOS.MOV

MOV File

1drv.ms

 

[Acard7]

Ya that’s your intermediate bearing that’s bad! Look it up on here, it may seem overwhelming but it’s actually fairly easy to change yourself!

 

[mbalogh]

Thanks, did some reading on it and it looks like a really sucky job but as long as I can get all the necessary bolts out without incident I don’t see why I can’t get this done. Any suggestions for where to purchase the bearing housing assembly? I’d rather buy one preassembled then try to buy the individual parts, which end up more expensive anyway, and try to put it together myself myself. And I want quality parts, don’t want to be doing this job again in a few years.

 

[Acard7]

Thanks, did some reading on it and it looks like a really sucky job but as long as I can get all the necessary bolts out without incident I don’t see why I can’t get this done. Any suggestions for where to purchase the bearing housing assembly? I’d rather buy one preassembled then try to buy the individual parts, which end up more expensive anyway, and try to put it together myself myself. And I want quality parts, don’t want to be doing this job again in a few years.

ISLAND RACING

There’s the link where I bought mine. Email The guy to make sure he has either the west marine brand or the island racing brand in stock as you scroll down to find the intermediate housing bearing!

 

[mbalogh]

Awesome, thank you! Hope it gets here by the weekend but somehow I doubt it.

 

[mbalogh]

I ordered the part from Island (via email… ugh) yesterday and have received no response. Do they send you any confirmation? Shipping info? Anything? Or does the part just show up? Don’t want to spend a week waiting to find out it’s not coming.

 

[HawaiiBreeze]

Going back to original problem I am wondering why the boat at full RPM 8k is wallowing. The engine/pump is direct drive so 8k rpm at the engine is 8k at the prop. If you've never experienced cavitation its like the engine winds up but you are spinning air not water and there is a heck of a lot of vibration. I am wondering if your engine and the mid shaft or the mid shaft and the pump shaft are not lined up properly. Seems improbable but you've kind of eliminated the most obvious and most common areas. Make a thorough inspection of the pump and prop too while you are doing all this. This should be an easy symptom to track back to the source.

Good Luck on the replacement of the bearing housing. On a PWC they arent that bad however the cramped engine compartment on our boats is another animal.