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Sea Doo Speedster Mid range power cut....

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DonalMW

DonalMW

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Hello, first post here,
I have a Sea Doo speedster with 2 x 85 hp Rotax engines, it's a 1999 boat. My problem is this, while accelerating on both engines the power dies and occasionally cuts out at approx 2000-3000RPM. Can anyone shed any light on my problem??
Also it takes maybe 20-30 seconds to start each engine, but they always start so I can live with that.
I replaved the REVE valves last year thinking they might be the problem to no avail, also I replaced the fuel filters with no sucess either.

I have 3 trains of thought, 1: The Carbs.
2: Throttle Sensor??
3: Fuel pump??
I don't know if there are numbers 2 and 3 in my boat??
I've had a few great days on my boat, but for pulling skiers it gets VERY frustrating......

Is there 2 throttle sensors for the 2 engines??

Anyone know a good website to order spares?? I'm in Ireland but don't mind ordering from the USA, this is where my boat came from originally.
 
Welcome to the forum....

Welcome to the forum.....always glad to see others from around the world come in.
Let's get right to your issue. First off, let me make you a bit more happier. Your boat does not have the lower powered 85 hp, 717 cc Rotax engines. Your boat is equipped with the twin 787cc engines with 110 hp each. For a total combined 220 hp. This is a nice boat!....
I've got a couple questions becuase this is a twin engine boat and the syptoms, if it were a single engine, point toward your accelerator pump. But what's the chance that both go bad at the same time. The other thing is, both engines have their own fuel pumps. They are located on the MAG carb and they operated by a pulse line connected to the crankcase. So once again, what's the chance that both have gone out at the same time.
You don't have a fuel sensor, so I'm just a bit stumped as to why both engines would do this. I do have one thought. Both engines are fed by one fuel tank. If you have any loose fittings between the tank and the engines, or the vent is stopped up, or there is trash in the pickup tube assembly. That's the only way I can come up with the idea of both engines doing the same thing and the "hard" restarting.
Is there anymore detail you can give to us that might help? Most forum members use a distributer called babbitts and there is normally a link to them on our home page.
Re-post with any additional you can to help out. Has anyone messed with the fuel lines coming from the tank?
When running the boat, when this occurs, pull off your gas cap and see if you hear any vacuum sounds.........or pressure sounds.....if your vent isn't working, you can tell by removing your gas cap. There shouldn't be any sound what so ever..........
Get back to us!.....
 
Thanks for your quick reply,
In answer to your question,
The problem since we got the boat was on 1 engine, it was troublesome from the start, th other engine was only slightly flat-spotting but they're both equally bad now.
 
Thanks for your quick reply seadoosnipe ,
In answer to your question,
The problem since we got the boat was on 1 engine, it was troublesome from the start, th other engine was only slightly flat-spotting but they're both equally bad now.
I have the parts manual in book and cd-rom form.
I like the sound of the accelerator pump being gone, it sounds like the problem to me, is it a straightforward job??
I was told by the person I bought the boat from that they were 2 85 hp engines, but the person in question didn't know much about boats!!
Once you get over the flat spot in acceleration ( Which can be tricky) the boat will do 50 mph, is that right for a 220hp boat?? Seems really fast to me!!
And thanks again for your kind response, It gives me a few more ideas to look at.
P.S It wouldn't be a throttle position sensor, I read about them somewhere else here, I think that was on a jet-ski tho.....
 
Tps....

I don't know that the TPS sensors are on these engines. If you read about it on the 787, it may have been the newer RFI models. A fuel injected engine has the TPS (throttle position sensor).
If one engine was running a bit sluggish, then the other. You might go ahead and do some fuel checks on one engine, in other words, lets work one engine at a time.
Take off your black plastic cover on your flame arrestor, then you'll need to take out the metallic flame arrestor screen. Then, you should be able to see the throats of the carbs. On the PTO carb, is where you'll find your accelerator pump. It will have a small (about 1/4") hose coming off of running under the bottom side of the pto carb, then it will come to a "t". There, you'll see one of the hoses go up to the top side of the pto carb and the other end of that hose on the tee, going to the same area of the mag carb.
NOw, to do this test, you'll only get a couple shots at it because of the amount of gas stored in the diaphram area of the fuel lines. Seeing inside the carbs, where those little hoses go to, you'll see in the throats, a small brass needle. With the choke open so you can see inside, use one hand to roll the throttle cam open. When you do, it's cammed to the accelerator pump. You should see (and hear if it's quiet) a small stream of fuel being squirted into the carb. Check both carbs and let me know what you find out. If you have the manual, look into the fuel circuit section and this part will be explained.
 
Wow, thanks for the info, i'll print it off and get some1 more mechanically minded to have a look, carbs scare the hell out of me!!
I'll let you know my results.
Many thanks again.
 
Carbs...

I have the same Mikuni BN 40i carbs that you do, then I remembered mine were sitting on my work bench, so I went out and took you a couple pix of the accelerator pump jet and the pump itself. May make it a little easier.... Just click on the attachments!....
Good luck.
Oh, and if the accelerator pumps are o.k., you may look at the carbs filter. Their inside the carb and about as big as the end of your pinky finger. It may be time to go through your carbs and clean them out. I'm not saying that's your problem, but it's as good a place as any to start!....
 

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Thanks, the pictures will make this job easier for me to identify the pieces. I hope to get theese problems iorned out for the new season, the weather should be picking up in a few weeks........I predict some boating!!
 
Carbs....

Well, like I said, that may only be an idea of where to start. It may be the only problem, there may be dirty fuel strainers inside the carbs or you may need a rebuild kit becaue it's just their time. The only issue I had is how all 4 carbs would be in this situation at the same time. But then again, if they gummed up, that could happen to all 4........
Good luck and let me know how it comes out or if you need somemore info....
 
Just starting this repair at the moment. I'm having trouble disconnecting the throttle cables?? I'll probably have it figured out by the time there's a reply here.
I'll keep this updated as I progress
 
I was thinking that, but was afraid a spring might unload??
Also, is there a wakeboard tower avilable for my boat model??
Can it be bought online??
Is it expensive??
Easily attached/removed??

Thanks guys
 
Nice Tower link, thanks!!
*update*
I got a relitive to dismantle the carbs, he has years of boat and motorcycle engine experience.
Apparently the carbs were in a bad way........
Also, while taking them out the Rotary valves were in a state also,
So i'm expecting the parts in the post any day.
The rotary valve setting tool was CRAZY expensive....
But necissary....
 
Hi guys, boat back in the water today and performing fine!!
50mph.... perfect, no "lumpy" acceleration...

1 issue, i might create a new topic, the fuel gauge has never worked.....and it's not a fuse problem..... Any ideas ??

Many thanks for the help b4 guys.....

Really apriciate it
 
Hello...

As stated above my boat now runs perfectly...

But it is still difficult to start, say 20 - 30 seconds before the engine fires, and maybe another 6 or 7 starts before she'll run...... on a fast tick-over and after a min there's no further problems.....
It's always been like this and I didn't think too much of it untill the last day a lad launched his challenger 1800 and just pressed the starter once for maybe 2 seconds before the engines jumped into life.........

I investigated the fuel gauge problem a little the last day....

All the wiring behind the instrument seems perfect, never tampered with.....

Where should I look next ??

Also on the passenger side of the boat in the storage area there's a 4 or 5 pin socket..... Any ideas what this is for ??
 
the socket may be for hooking up a radio.
The fuel gauge is likely the sender in the tank (search the forum, hundreds of posts on the subject).

As for hard starting, check that your chokes are properly pulling open the choke plates in the carbs... with the air cleaner pulled back off look into the carbs and have a buddy pull the choke cables on the dash.

Also, what are you doing when you start it?
Pretend you are in a carbureted car, you pump the gas pedal a couple times first. Do the same thing here, push forward and back on the throttles a couple times first. Then hold the choke fully pulled out while pressing the start button.

Also make sure the start button is starting the same engine that you are choking, maybe one of them is swapped so you are holding choke on the wrong engine? They should start easy, 10-20 seconds when cold, less than 5 seconds when warm (no choke, only pump throttle)
 
Thanks....

Lots of options to explore there.....

To start I always just pull the choke ant hit the starter....

Then alternate between choke on / off until it gets going....

Thanks again vilord, i'll hopefully do some investigating / experimentation during the week......
 
Well I took mine out today and it was definately harder to start than I remembered.
But another suggestion would be to start it on the trailer when you are prepping (it can run 10-20 seconds without any cooling water).
That way it doesn't have the back pressure of the pump to keep it from getting going.

That Challenger 1800 you mentioned might be doing that.
 
Buddy its time for you to check your gas tank baffle pick up thats the reasons why fuel gauge are not working properly or not work at all.:cheers:
 
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