97 Seadoo Challenger 1800 Super fuel consumption

[SMLseadoo]

Hey all,

Bought my first boat this summer a 97 seadoo challenger 1800. I took it out once and made a 16 mile round trip and burned through 30 gallons of gas. Needless to say it hasn't left the driveway since. I know these boats aren't known for the mileage but I think that's a little excessive.

I'm thinking its the carbs and possibly the rave valves but I'll list the symptoms and see what the consensus is.


The Patient:
97 Seadoo Challenger 1800
Dual 787 engines
Previous owner had lower ends rebuilt.
Someone at some point has had at least one of the carbs off the engine (I started taking them off planning on doing a rebuild found orange silicone between carb body and block)

The Symptoms
Excessive fuel consumption
Fouling plugs
smelling gas when the boat is idling
Won't rev up correctly. (New plugs boat hits 7k after riding it for a while especially after cutting it off and restarting you are lucky to get 4k out of it)
You can forget pulling anyone on a tube. Pulling the tube and 2 90lbs kids was like hauling the titanic.

 

[LouDoo]

Hi and welcome to the Seadoo forum.

Well your boat is not going to get good fuel mileage but you should be doing better. From what you're saying I suspect you are experiencing cavitation, which means that you are over-revving and not going any where. Like if it were your car the clutch or transmission was slipping.

The first place to check is the condition of your wear rings, there should be no more than .040" clearance between the wear ring and impeller. Here's a how-to on replacing the wear ring.

http://www.seadooforum.com/showthread.php?30720-How-To-Changing-Your-Wear-Ring

It also sounds like you may have fuel delivery problems, does your boat have grey tempo fuel lines. Here's another thread on fuel delivery problems.

http://www.seadooforum.com/showthre...el-Delivery-Problems-low-revs-bogging-surging

I'm moving this thread to the 2-stroke sport boat forum.

Lou

 

[SMLseadoo]

Sorry about posting in the wrong section.

I don't think its the wear ring, because its not like I can always hit 7k and the boat is setting still like the transmission was slipping.
The last time I went out I put in new plugs boat ran like a champ I was able to do 4-5K and then open it up(7k) once I got out of the cove. Got it to plane and backed off the throttle. I could give it more gas and the rpm would come back up. Then I stopped, and let the boat idle for 5 mins approx while the kids were getting on the tube. I began to smell gas like the engines are running rich so I cut the boat off with the kill buttons. Got the kids happy started it back up no choke needed or anything and started down the lake. At that point I could only get the engines to rev to 5k and it felt like I was pulling another boat. I stopped pulled the plugs they were really dark and smelled of gas. I wiped them down and tried to use a lighter to dry them out. This was done to all four plugs. Restarted the boat and hit full throttle engines responded better with about 6.5K rpm. Once on plane I throttled back, realizing I had throttled back too far tried giving it more gas to get back on plane but the engines wouldn't respond back to 5k at WOT. At that point I was at a loss and headed home the closer to shore the worse the rpm got constantly falling. Thinking it was a rave valve sticking I was working the throttle on each engine trying to get it to free up but the rpms never came back up. By the time I hit shore the Left engine was 4k at wot and the right was at 5.

 

[racerxxx]

Your fuel consumption is horrible, honestly the fuel consumption is not bad on these boats. I towed two boys on a tube for roughly 3 hours of tube time and burnt probably 13ish gallons. I can go on a 40+ mile run with about an hour of tubing and not burn 1/2 a tank (20 gallons), about 5k cruising is the sweet spot. You can easily get a day out of a tank of gas. I regularly go out for a nice long cruise and come back before I hit reserve.

You need to go through the carbs and rebuild them, genuine mikuni parts and even the needle and seats need to be replaced. If I understand correctly you are not moving fast but the engine revs like Lou mentioned?? You need to make sure you pump the zerk fitting on the PTO to push the driveshaft back, also you need to look at the wear ring and check the clearance. Also on the pump support (the black plastic part that stays mounted to the boat) is supposed to have a neoprene seal to seal the pump to the pump support--another point of air leaking for lack of better terms which will create cavitation. With a properly set up Challenger you should be able to jam both sticks forward and the boat will take off and just GO. No flair up of cavitation--nothing--just GO.

The bad news is you need to dump some coin into this boat to get it operational to 100%. These boats are a TON of fun when operating 100%. We'll do our best here to help you out. Welcome to the forum, where are you located?



Here is a good thread on alternative fuel pumps
http://www.seadooforum.com/showthread.php?63577-fuel-pumps


I have some pics in here of a Challenger I repowered for a guy. You can see the pump support, neoprene seal and what bad wear rings look like and what a good one looks like.

http://www.seadooforum.com/showthread.php?61486-Big-thanks!

 

[racerxxx]

It also looks like you have dual fuel selector switches, add the to the replacement list. Some guys clean them, I throw them out and replace them.

 

[SMLseadoo]

I am not having the issue where the boat revs but doesn't go anywhere. The issue I am having is that the boat just looses RPM at WOT it will not redline.
If/when I can get 7k out of it the little thing will scoot.

I think with it fouling plugs and sucking down fuel I'm going to start with the carbs.

While I'm waiting on parts to come in I'll check out the wear ring and other issues.


Can you point me to a rebuild kit for the carbs? I would also like to service the rave valves while I got the engines down. I remember reading on a forum post on here, there was a jet change and a revision to the rave valves through the boats life time. Will the new carb kit come with the correct jet? (it fixed a hot start issue. Sorry I forget the jet number) Should I get the new style rave valves?

Oh I'm in Roanoke Va

 

[racerxxx]

Gotcha on the revs now.

MK-BN38/44 SPR is the part# for a Genuine mikuni rebuild kit. Now I'm almost 100% certain the your needle and seat are 1.5's. I just bought are part# 786-35015-1.5 These have a Viton rubber tip that is supposed to be better with the ethanol in today's gasoline.

I bought my stuff from http://www.nichecycle.com/ncs/ They offer free shipping over $100 and they shipped the same day priority mail to me. I shopped thee all over and after shipping most places are with in a few bucks, but this place had every jet I needed in stock. Before ordering kits I suggest you pull the carbs and look them over to make sure someone hasn't molested them already. Take pics as you disassemble so you know how they go back together. REUSE your original springs INSIDE the carb unless they have been cut or deformed. There is also some other stuff to go along with the cabs like a pop off test but digest this stuff first. I think there is a good thread about the carbs in the tech how to section on the forum.

Rebuild kits--1 per carb
http://www.nichecycle.com/ncs/categ...38-44-46-sqr-38-40i-rebuld-kit-by-mikuni.html

Needle and seat again 1 per carb you would order the sendon one on the list the -1.5
http://www.nichecycle.com/ncs/categ...86-35015-viton-tip-needle-seat-by-mikuni.html


There is also www.OSDparts.com that has genuine Mik kits but it's more of an A-la-carte deal. I just buy full kits. Your PTO carb won't need all the same as the MAG carb so you will have a bunch of extra parts afterwards. I'm pretty sure your boat still uses the fuel pumps ON the carbs, the later boats switched to divorced fuel pumps from the carbs.


As far as a jet change with the raves, just reuse what you got. You can get the parts at your local dealer if you want Inspect the bellows to make sure they are in good condition. The site sponsored seadoo parts can also get you that stuff if you want to go that way

RAVE O-ring 290430110 2 per engine
RAVE Gasket 290931540 2 per engine
RAVE Bellow 290260728 2 per engine IF NEEDED LAter ones are Green early ones are Redish. I always swap them out to the green ones. SBT also sells a complete kit with o-ring, gasket and bellow cheap as well as 100 guys on Ebay, I prefer mine to be OEM.


LOL, I think that kinda covers it, for now.....

 

[MM800]

Greetings, Im new here. Anyways, Im new to the jet boat sceen, but have over 20 year dealing with snowmobiles and carburation. Going from high elevation to low elevation took some jetting changes. Anyways seems to me that you are over fueling. Over fueling can cause the motor to load up and or foul the plugs. From past experience, a fouled plug never comes back to new no matter how hard you try to clean it up. It will work,but near as good as new. Thus the reason why your motor seams to run better with new plugs. Its a good chance that you are running rich, jugging by your fuel issue (using alot) and plugs loading up. A rebuild as other member suggested is a good place to star. Take notes of all your settings and post back. Also a bad needle and seat , wrong size of needle and seat can cause a rich issue. I dealt with the same issues you had last summer. Mine turned out to be the wrong size needle and seat. I had a 2.0 and should of been a 1.5. I was able to play with the fuel shut off switch for the right motor (94 speedster) and get it to clean up a bit. However, I DO NO RECOMEND DOING THIS unless you fully understand what is happening. You are leaning the motor out. TO much and you will burn it down. So, clean the carbs, take notes of all your settings. There is alot of good info on this board for the proper settings and how to do it. Good Luck and post back.

 

[SMLseadoo]

Thanks for all the information guys.
I took a flashlight to the pumps last night and inspected the wear rings. They looked smooth and in good condition. I'll try snaking my hand up the inlet with a feeler gauge to check the tolerance.

Oh here is that other post where a guy is talking about a Factory update to the carb jetting and rave valves.
http://www.pwctoday.com/showthread.php?t=230456

I got one set of carbs off the boat already. I'll start the tear down and see how they look.

 

[SMLseadoo]

Thanks for all the information guys.
I took a flashlight to the pumps last night and inspected the wear rings. They looked smooth and in good condition. I'll try snaking my hand up the inlet with a feeler gauge to check the tolerance.

Oh here is that other post where a guy is talking about a Factory update to the carb jetting and rave valves.
http://www.pwctoday.com/showthread.php?t=230456

I got one set of carbs off the boat already. I'll start the tear down and see how they look.

 

[SMLseadoo]

Going to try tearing down the carbs this weekend. And get the rebuild kits ordered.

I found the forum post where it talks about these boats receiving a factory update that consisted of different carb jetting and a change in the rave valves.
But I can't post the link, if I do I get a message about the post needs admin approval or something like that. I've tried pasting it as a link and just as text and it happens both ways.

 

[SMLseadoo]

http://preview.tinyurl.com/qe88maz

Ok here is the link I just made a tiny url and it went through. It is to one of the other seadoo forums.
If you read down to the reply made by grumpy old guy he informs the reader of what changes was made and then goes into detail later in the post.

 

[SMLseadoo]

Hey All,

Been a while but I've made a little progress. I removed one set of carbs and tore them down.

Looks like I had a restriction on the PTO carb. I don't know if this is the fuel inlet or return to tank it exits out on the elbow/nipple that leaves the carb body at a 45 degree angle.

Can some one point me in the right direction on the Low speed and High speed screws?
Is this the high speed with the H stamped on the carb body?

The high speed setting is supposed to be 0 is that right? (I've read so much stuff its all running together)

 

[hotrodssnova]

Have you downloaded a service manual yet? It will tell you almost everything. I even have it on my phone so I can see it when and if I need it on the water.

 

[SMLseadoo]

Thanks hotrodssnova, I checked the service manual and it was a wealth of information.

It appears my problem is (at least on one set of carbs) is that the return line orifice was stopped up so the fuel had no place to go but through the engine. That and the HS Screw was set at 1 Turn out.

I know the spec sheet calls for this to be 0, should I put it back to 1? What would cause it to be set at 1?

So working my way back to the tank looking for the source of the debris that clogged the carbs I noticed someone in the past removed the factory fuel filters below the oil tank and replaced them with clear inline fuel filters. But they look clean and all the lines look clean also. I have also checked the fuel lines they don't appear to be the gray ones just regular black rubber fuel line, so no issues there.

Being that the fuel filters are clean should I go through the trouble of pulling apart the fuel shut off valves looking for corrosion?

 

[hotrodssnova]

I just went thru that with my pto carb. It would foul the plugs after about 20 to 30 minutes. The best thing you can do is keep the fuel filters clean. That keeps clean fuel to the carbs. If you have the type that separates water also, that will help keep corrosion to a minimum also. With the ethanol fuel, it helps pull moisture from the air, and it will pool up in the tank. Marine sta-bil helps. I use it in every tank fill. I also clean the filters after every tank of fuel also. It's always humid in Houston!

On the selector valve, it couldn't hurt to clean them. It's always nice to have piece of mind that the system is clean.

 

[LouDoo]

This may be of little consequence, but at least on our lake non-ethanol gas has become the norm. I know of at least five marinas that sell nothing but non-ethanol gas. We keep our boat at the lake so I use only non-ethanol gas. It is more expensive about $1.00 more per gallon, but worth every penny, also it's 90 octane. So you may want to check in your area and start using gas at the lake instead of from a service station.

Lou