1997 Seadoo Sportster HALF Acceleration and NO Plane on boat.

[Fred1948]

Hi everyone. I'm new to this forum and am looking for tips/help on my 1997 Sportster.

It goes to about halfway on throttle, then dies back
Cannot get the boat to plane out or reach the rpm needed!
Below are the things that have been done to it recently per suggestions by local seadoo man.

He now is suggesting I try changing from dual carb to single carb.
IS THAT A GOOD IDEA? HAS ANYONE EVER DONE THIS WITH SUCCESS?

Rebuilt both carbs, and checked them 3 times.
Popoff working good at 25 PSI.
Low side adjustment is 2 turns out, the high side is 1/4 turn.
I've tried many different combinations on adjustments, even while standing in the engine compartment!

I've checked for fuel line blockage, but don't see any problem.
Sending unit in fuel tank has been cleaned out.
The shutoff valve has been bypassed.
Could there be a fuel blockage?

Any ideas will be helpful!

 

[robomatic12]

What did you use to rebuild the carbs? Cheap aftermarket kits like Windarosa? I had endless issues trying to get aftermarket carb kits to work properly, ended up with OEM Mikuni rebuild kit with new needle valve and seats. Runs perfect.

 

[Fred1948]

Yeah, afraid that might be the issue.

Bought kits from SBT, with New needles and seats.
Good or Bad? in your opinion

 

[Waterluvr]

Don't change your carbs to a single Fred! :facepalm: You came to the right place, we can help you get it running right.

Ok, scrap what the Sea Doo local told you and let's start with a clean slate and get it diagnosed properly ok? The very first two things to test / verify is cylinder compression and ignition on both cylinders before moving on to the fuel side of things, you're running the 85hp 717 without Rave valves correct?

Post your compression numbers for both cylinders and at least visually verify both plugs are firing. Also, check your spark plugs and verify they are the correct plug number for your engine with the R marking to indicate both plugs have the proper ceramic resistor. Parts guys slide sets of plugs across the counter all the time and get them mixed up, so it's easy enough to buy the correct number and still get the wrong plug.

It would be a big help if you have a shop manual for your boat to reference testing procedures.

 

[smc0922]

You're going to want to verify your jet sizes. I have the FSM and can get you the right numbers. You're going to want to buy 2 genuine mikuni rebuild kits and use genuine mikuni valves and seats. There goes $200 in parts. Always always use genuine mikuni parts. Afterward, set your needles to the right amount of turns. 2 low and 1/4 high are rich. It's either 1 1/4 or 1 1/2 low and 0 high.

 

[Fred1948]

Waterluver, thanks for the good suggestions!

I will check the compression in the cylinders tomorrow and post it.

I'm running the 85 hp 717 Rotax. I don't know about the valves. BUT, the engine was rebuilt last year by someone other than me.

Spark plug numbers are BR8ES - ngk and below the ngk is a R.
This is how the plugs are firing: the pto/piston side is black.
The other cylinder's plug is light brown.
So what do you think?

The coil is a NEW $170 coil from Seadoo, just a couple of weeks ago..

 

[Waterluvr]

Waterluver, thanks for the good suggestions!

I will check the compression in the cylinders tomorrow and post it.

I'm running the 85 hp 717 Rotax. I don't know about the valves. BUT, the engine was rebuilt last year by someone other than me.

Spark plug numbers are BR8ES - ngk and below the ngk is a R.
This is how the plugs are firing: the pto/piston side is black.
The other cylinder's plug is light brown.
So what do you think?

The coil is a NEW $170 coil from Seadoo, just a couple of weeks ago..

I think one brown and one black are a sign of trouble, to what degree or where to look is why we always start with compression and ignition before we diagnose the fuel side of things.

Right off I know your carbs are not adjusted properly, the procedure for those settings are specified in the manual and you won't deviate far from those at all in order to get peak performance.

Let's look at compression, your plugs are correct and if there's any way you can get your hands on a CDI rated ignition tester that would help to just verify that side of things. So long as compression is in spec and ignition checks out your issue is in the fuel system and we'll start by testing the supply side of things to the fuel pump.

 

[Fred1948]

Whoa. I've torn the carbs apart 4 times, but never thought to get the jet numbers.
Let me try resetting the needle valves as you suggest and maybe that will work.
If not, and I end up taking carbs apart again, then I'll have opportunity to check the jet sizes.

Can't believe all the tips I''m getting from everyone in just a few minutes. Thanks again!

 

[Fred1948]

Hey Waterluvr,

You suggested a compression check on this 717 engine. It reads only 100# dry, and 115# wet.
The engine was rebuilt by SOMEONE? in Pennsylvania 2 years ago.

First time out this year, the boat ran like a dream, except smoking like heck on startup, which had been going on for about 2 or 3 yrs previously. I thought the rebuilding of the engine would cure that problem, but it did not.

Second time out this year, no smoke on startup --- the only thing to report was after launching in reverse a ways, wife noticed a low growling noise coming from engine that we'd never heard before. We skirted the bay and it seemed to be running ok. We had a nice boating trip with a few stops in between. Later, we suddenly had trouble starting up. It acted like it didn't get enough fuel, had to use the choke and then feather the throttle before steady running in neutral. The boat ran smoothly after that back to the dock.

A suggestion was made to me by SBT tech support that the needle and seats were probably bad causing the smoking problem, so I rebuilt that part of the carbs. That did stop the smoking.
I thought the problems were solved, the boat started right away, and planed nicely and quickly and we went maybe a 1/2 mi and suddenly the boat began chugging and losing power. We limped back to the dock seemingly running on just one cylinder! I checked the spark and didn't see any.

I asked local seadoo man for suggestion of WHAT could be wrong now? He said probably the coil needed replacing. So I installed a brand new one from Seadoo. Now I had sparks but no acceleration past 1/2 throttle to plane the boat.

Then conferred with Kentuckiana mechanic for Seadoo, and he asked where I got the carbs from.
He thought SBT's were junk and the diaphams were too heavy, so I bought 2 new diaphrams from the dealer and compared them with the SBT's. I couldn't see any difference so returned them to the dealer.

Now there's LOW COMPRESSION.

Question: are SBT parts good to use?
Does anyone know what that low growl noise (which stopped shortly after started) could be?
What can I do about the Low Compression?

Thanks to anyone who will reply!

 

[Waterluvr]

Well, there's no getting around 115 pounds of compression and the motor is in need of evaluation and overhaul at this point. Now you know why I always start with a compression and ignition check before moving on.
The noise your hearing could be anything from a bad bearing, broken piston ring or? The only way to find out is to open it up starting with the cylinder and piston components for inspection.

If you want to verify the compression with another tester please by all means do so for your piece of mind going into it but 115 pounds is far to low and any further use of the engine may cause considerable damage at this point. You may find it's a simple fix just requiring a fresh sleeve bore and pistons to remedy the situation if the crankshaft, bearings and rods are ok.

I only use genuine Mikuni service parts to rebuild carbs and pumps, I'm no fan of SBT's engines or rebuilding practices and wouldn't use their carb kit's either but some of their gasket sets and driveline rebuild kits are a good value and reasonable quality.

 

[Fred1948]

Thanks. The low compression explains much.

I don't have the tools to work on a Seadoo engine, so the boat is worthless for now.
Can you recommend a reliable rebuilder?

 

[Waterluvr]

Thanks. The low compression explains much.

I don't have the tools to work on a Seadoo engine, so the boat is worthless for now.
Can you recommend a reliable rebuilder?

I can, and would be curious to know if there are any markings on the engine to indicate who did the work last time around? You may find a tag on the front side of the engine by using a mechanics mirror to see in there. There is a very reputable rotax engine builder in PA (The Seadoo Engine Shop Horsham, PA) that does good work and I prefer Full Bore up in Alpena MI for complete rebuilds.

If you want to see inside the cylinders it's a simple matter of just removing the bolts on the head and pulling it up and off to expose the tops of the pistons and have a look at the cylinder walls. That alone is very telling on most issues like yours.

 

[Upallnight]

I had a similar problem, couldn't get the boat up on plane, rebuilt the carbs and that didn't help, rebuild another set of carbs and that didn't help. So this season I decided to rebuild the engine. When I went to remove the flywheel from the crankshaft it was nowhere near the 135 nm and a metallic part fell out on the metal pan that I place the engine on to disassemble. Turn out the woodruff key to the crankshaft had sheared and timing was completely off.

 

[Fred1948]

Thanks for your input, Upallnight!

That will be my last resort, tearing the engine apart.
Hope I can figure it out before that's necessary, but I will keep your experience in mind.

 

[Fred1948]

Okay. Well, I remember it was the builder in Horsham, Pa. the Seadoo Engine Shop.
The boat was running fast and smoothly most of the season last year, after the rebuild.

One thing I have not mentioned was the overheating of the engine, so that's when I had the impeller pump rebuilt end of season last year. The wear ring was bad and the impeller nicked up a bit, which he just smoothed out. The bearings were ok so he just changed the oil in them. All that brought us up to beginning of this season when the boat ran GREAT first time out, and then on the second time out -- until the trouble with restarting after sitting in the bay, as mentioned.

Today, I borrowed a NEW COMPRESSION GUAGE from O'Reillys.
Dry tested, the cylinders were both 130#.
Wet with oil, the cylinders were 180!
Yesterday I was using an old compression guage from 35 years ago -- where I had to hold the guage in the cylinder! Not accurate whatsoever, and it's going in the trash can.

So, engine rebuilt.
Impeller rebuilt.
New Coil is good -- while spark plugs were out, I could see very bright spark. The guage showed a jump of an 1/8 inch in both cylinders.
Spark plugs are correct type, though I may buy some new ones to retest boat.
Carburetors rebuilt, but problematic I think.

Mechanic friend of mine thinks the high circuit of the carbs may be plugged up with something, so will check if that is holding back fuel and keeping the boat from planing.
Also, will reset high and low to factory specs, take out one more time on lake and hope for the best.

For now, thanks for all your tips!

 

[Waterluvr]

Good to know, SES stands behind their work and you would want to have a talk with them before opening anything up depending on the warranty terms of your motor.

Those second compression numbers are so skewed it's hard to even take them into consideration (especially the 180 numbers) but it's still encouraging. I use a Matco compression tester with the appropriate thread length adapter to match the plug depth to check compression on these motors. I would use a third gauge if possible, anything made by Snap On, Matco etc if there's a chance of obtaining one.

130 is a bit low but it ought to run and be tuneable to some degree of satisfaction, I believe a fair number on these motors is only achieved after running them and bringing the engine to operating temperature and testing them right away to avoid cold pistons and alternatively false readings from adding extra oil sealing the rings bearing surfaces.

All in with adequate compression and the ignition & plugs checking out it sounds like you put just enough time on it this season to pull something from the fuel system into that side of it that's giving you the current grief.

Before getting into the carbs I always hook a Mity Vac pump and recovery cannister to any fuel supply line to test for uninterrupted fuel flow and visually see any contaminants coming into the cannister. On these boats the fuel selector valves are known to be problematic and they should be tested on both the on and reserve settings and should stop the Mity Vac from pulling any fuel right away when set to the off position.

If there's any doubt to the integrity of that valve replace it, the failure rate must be rampant on them as SBT offers a low cost replacement. I know you mentioned bypassing the valve in your original post but I would revisit that and double check everything and the line routing to the fuel baffle connections for proper location.

From there if it passes a fuel supply check you should remove the impulse hose from the case and fuel pump and vacuum test the hose from a T and two lines / nipples going into both ends. Any cracks or leaks in the impulse hose is going to interfere with fuel delivery to the carbs from the pump and will cause erratic operation.

From there the carbs and fuel pump get opened up. I've seen carbs rebuilt 4-5 times by frustrated guys that don't check the supply and impulse functions first and it only takes a couple extra minutes to do it right the first time and avoid the rinse and repeat of servicing carbs that aren't the source of the problem.

 

[martin18152]

This sounds like a carbon copy of what is happening on my boat, I hate to hijack your thread, but hate to start another on the same issue.

The boat will idle reliably, but when you go to half throtle , or the transition from low to high, the engin bogs, its alsmost like your running on one cylinder. I had one wet spark plug, and one dry- attributed to spark plug fowling. Replaced both spark plugs, and the boat ran the same. This just happens on the left engine. I have a lot of trouble shooting to do, but I will follow this thread to minimize it.

You mentioned that a lot of smoke comes out on the season start up. I had the same issue, chances are that the crank shaft seal is failing and the oil is getting in the crank. These engines have direct oil injection at the crank bearing. You just can't replace the seal, you have to replace the entire crank , it cost about 300 pluss dollars, I dont think they have them in stock, so they have to build them. If the engine was rebuilt and he did not put in a new crank, this could be your problem. Eventually you will get so much oil in the crank, your pistons will hydro lock, and you could bend you crank. I would recomend you put a clamp on the hose durring storage, you can live with this problem for a while. Dont forget to remove it in the spring.

 

[martin18152]

I also would like to address your comment on the engine noise, you may want to check you exhaust valves, every one of mine were broken in both engines, one engine had a stuck one that was rattling around in slot, sounded like a bearing coming apart. The one that broke from the stem, was blocking the exhaust port, and caused the engine to cut out or stall at high RPM. I put all new valves in the engine last summer, and hardly ran the boat, I am going to check them anyhow. They are SBT , they may have already broke, I hope that is the problem, this is an easy fix.

 

[howie099]

You could be sucking air also in your fuel system. Those crappy seadoo fuel filters leak all the time at the rubber gasket. Toss them and get a plastic Fram one from walmart for like $3 or a good aftermaket boat fuel filter. I run these all on my water crafts. It think the number is like G2 or something like that. It is posted in the forums here. If you have low compression game over. If you have decent hours on it you can do a top end to save some cash.

 

[martin18152]

Had the same problem, looked at the fuel filter on the problematic engine, the filter had some gas in it; however, it was a less than a quarter of the other engine. So it was a fuel problem, that could be at the pump side, or the carb side. I have had a problem with pumps before, the problem is that when they paint the pumps black, they also paint the inlet port, and the gas breaks down the paint, and it ends up in the carb, or pump. Took the fuel pump out (not an easy job) , cleaned it out, put it back on, took it out to the river. At first it did the same thing, started to bog down at above half throttle, pulled the choke at wide open throttle, the engine cleared and went to full revs. The boat has been running for hours the best ever. My guess, there was a blockage either in the high speed jets, or the pump, and it broke lose. My advice is to check you fuel filter, if you have a clear one, it should be at least 3/4 full after a run, if it's not , pull the pump, clean it , if that doesn't work, clean the jets. You can rebuild carbs all day long, and if your sucking in paint chips from the fuel pump nipple its going to clog again.