Mercury Sport Jet 90 Engine Problem need advice

[aksor]

Hi guys and gals

I just bought a 94 Sea Pro Renegade jet boat with the 90 hp Mercury Sport Jet for $400.
The lady I bought it from said it starts then shuts down she took it to the marina and they told her it will cost her $2000 to get it fixed.

When i got it it was missing the flywheel so I took a chance with it not even knowing if the motor was seized or not hence the price i paid

I found out where she had it serviced and recovered the missing flywheel and also talked to the mechanic and he said fuel was spitting out of the carb's so he said it points to damaged reed valves

So i took the intake apart and took the reed valves out for inspection none are missing petals but out of the 3 2 of them one side don't seem to seal properly if I point them toward a light source i can see light shining trough!

My question is do I need to replace them or are they still good for a while? Would this cause the start then stop issues I'm having or is it the magnet that came loose in the flywheel and was still there but there was no gap between the two magnets.

BTW the compression is good in all 3 cyl and the carbs are clean the vent elbows had some gunk in them but cleaned them out along with the vent hoses

I also noticed that the ride plate was not flush with the front of the hull so i removed it and straightened it out.

My other question is can I run the engine once I get it going without the ride plate in place to prevent another bend in case it backfires while I'm testing the engine?

Thanks

 

[bedwards36426]

Re: Mercury Sport Jet 90 Engine Problem need advice

Hey buddy. I don't know what happened to all the sport jet experts on here. Im no expert by no means but the bad reeds could cause you problems. I just sold my sea rayder with a sport jet 90 like two weeks ago and bought a brand new seadoo 180 boat. I do have a ton of parts on eBay. And I do have a set of reed valves on eBay as well the are obsolete. If you think that's the problem then holla at me. I don't like shipping outside us but for such a small package I would make an exception. If you think that the problem. Do you have a manual?

 

[aksor]

Re: Mercury Sport Jet 90 Engine Problem need advice

I got the service manual for it and I have to double check the reeds the manual says if they are open more than .010" then they should be replaced just have to check them with a feeler gauge.

Boysen makes power reed for the sport jets also

And having a magnet loose in the flywheel can't help much either.

 

[calledinsick]

Re: Mercury Sport Jet 90 Engine Problem need advice

Check the carb vent tubes if you havefuel spitting/running out. They are on the opposite side of the carb as the fuel line and are generally semi-transparent/yellowish. The fittings and the lines need to be cleaned (if they aren't venting the floats won't rise and shut off when the bowls are full). Clean the carbs and make sure the floats are functioning properly. Chase the holes for the vent passage/soak in carb cleaner.

The loose magnet- haven't had to deal with this but some people have re-epoxied them with sucess. Make sure its positioned correctly. (may be an outline on the flywheel from the old adhesive or measure precisely). Also needs to be low profile so as not to come in contact when spinning!

You say compression is good on all 3 cylinders...what were the readings? Please post. If they are good I'd say no to the reeds.

Big thing would be to check for spark (need flywheel in place). If no spark you have other issues.

To run out of water, check out this thread: http://forums.iboats.com/showthread.php?t=531752

Good luck!

 

[aksor]

Re: Mercury Sport Jet 90 Engine Problem need advice

Thanks for the reply I have been doing some reading and getting to know the engine. I checked the vent lines and you are right they were clogged up with varnish and so were the hoses.

I cleaned them out and will clean the carbs even though they look like new the was no dirt or varnish in the bowls.

I checked the compression after the intake was already taken apart so I'm not sure if that's a valid reading but 140 145 143 psi.

I also ordered replacement reed petals from Chris Carson Marine that are made of composite resin so in case of failure it wont trash the engine.

What is the best way to realign the magnet poles? and can I use JB Weld to epoxy it back.

Thanks

 

[calledinsick]

Re: Mercury Sport Jet 90 Engine Problem need advice

Compression is good.

I've never done the magnets, but I would comapare to the other magnets with a simple compass. As for epoxy, no idea. I'd keep it thin as the clearance is tight and make sure it is heat tolerant. Flying magnets have caused damage according to other posts.

 

[sschefer]

Re: Mercury Sport Jet 90 Engine Problem need advice

oops

 

[aksor]

Re: Mercury Sport Jet 90 Engine Problem need advice

Still waiting for my composite reed petals to arrive so I can reassemble the intake and put the carbs back on and give it a try at starting it up

 

[aksor]

Re: Mercury Sport Jet 90 Engine Problem need advice

Well I got some work done but the weather has been really crappy and cold we had 3" of snow a few days ago.
Here is what I did:

I cleaned all of the carb vents and replaced all the hoses with new ones, I JB welded the magnet back on the flywheel, got my composite reed petals from Chris Carson Marine and installed them on the reed blocks made sure to put some blue locktite on the screws.

I removed all the fuel recirc hoses and checked the elbows and check valves and found the bottom check valve was not closing so removed it and there was some sort of stainless steel wire inside were the ball is preventing it from closing. I managed to remove the wires and it looked like some s port of mesh but the valve closes as it should. I also replaced all the hoses.

I'm just waiting till tomorrow to start reassemble the intake, carbs, and flywheel and I hope she runs.

I currently have no ride plate because I'm waiting for the seal, Is it OK to start her up without the ride plate?

Anything else I should be aware of?

? Thanks

 

[aksor]

Re: Mercury Sport Jet 90 Engine Problem need advice

Little update today, I got the reeds and intake installed I also run the fuel recirc lines.
I got the flywheel put on and installed the top two carbs I still got to reinstall the switchbox and test the fuel pump to ensure that is working properly before I give it a test

 

[aksor]

Re: Mercury Sport Jet 90 Engine Problem need advice

For some reason I fell like I was talking to myself all this time.
But anyways i got It running yesterday and I guess I will figure out the rest by myself too

 

[calledinsick]

Re: Mercury Sport Jet 90 Engine Problem need advice

Wow. Your welcome.

 

[aksor]

Re: Mercury Sport Jet 90 Engine Problem need advice

It was not directed toward you I was just frustrated from the lack of reply's and I was half cut when I posted

Sorry for offending you.

 

[venxxxxx]

Re: Mercury Sport Jet 90 Engine Problem need advice

I got a few loose magnets around from my previous flywheel. I couldn't find any to replaced my 2 broken ones, so i bought a used flywheel. Let me know if you want one, I'll sell it to you. Pm me.

 

[calledinsick]

Re: Mercury Sport Jet 90 Engine Problem need advice

No problem. I'm just trying to help others out from my experience. Thought it was a little harsh! Glad to hear it's running!!

 

[aksor]

Re: Mercury Sport Jet 90 Engine Problem need advice

Venxxxxs I managed to JB weld the magnet back on and we shall see how it holds up but thanks for the offer.

Calledinsick she runs but the real test will come once I get her in the water
Will keep you posted!

Thanks for the advice much appreciated

 

[venxxxxx]

Re: Mercury Sport Jet 90 Engine Problem need advice

cool.. i used jb weld to keep the existing magnets on the new flywheel from flying off as well. It works wonder.

Any pics of your boat/engine ? curious

 

[aksor]

Re: Mercury Sport Jet 90 Engine Problem need advice

Ill take some pics on the weekend it's currently pouring rain

 

[aksor]

Re: Mercury Sport Jet 90 Engine Problem need advice

I was finally able to take it out to the water yesterday and here how it went!

It took me almost 18 minutes to get her started with the Champion plugs that were recommended in the service bulletin, No go so I put the NGK plugs back in but it seems like its getting way too much fuel and fouling the plugs. I finally was able to clear out the engine and started idles good. I did notice at one time trying to start it I had some smoke billowing out from the carbs is that normal?

I took her out for about an hour a few wot runs and she does get up on plane fast but after about an hour I noticed that the engine started to bog at wot so I had to keep it at 3/4 throttle.

It was not overheating as I was able to keep my hand on the heads, tried it again at wot and the same bog came back so I wrapped it up while waiting for my buddy to haul his boat out I was sitting idle and she sure likes to smoke.

After I took her out of the water checked the plugs and they were wet.

I have my idle air needles set to 1 1/2 out but did not adjust them yet could it be that my carb bowls are flodding and dumping too much fuel causing it to foul the plugs causing hard starts, what about the wot bog it was fine for almost 50min before it started?

I have a fishing trip coming up in early June I wanna make it work reliably

 

[calledinsick]

Re: Mercury Sport Jet 90 Engine Problem need advice

Bogging after running and running at 3/4 sounds like not enough fuel flow. I'd check the fuel pump flow- these diaphragms are known for failing. Pull the fuel line where it enters the carbs and place it in a jar/bowl. Crank the engine (don't start out of water) and check the flow. If it's pulsing, you'll need to replace the diaphragm. Not a tough job.