Blew up the sportjet 90 today!

[dmball]

So I went out on the boat today to enjoy the holiday weekend. First problem after the launch was the engine would not crank. So I jumped the starter solinoid and it would start up. So no big problem just had to use a screwdriver every time I wanted to start it.

Ran it most of the day and ran like a top. So I beached the boat next to my parents house boat and ate lunch. Then decided to go out and pull my sis and her boyfriend on the tube. So I start pulling them around and it was having a little trouble pulling them. Then it slowly died while cruising like it lost fuel. So it drove back to the park but had little power. I could get it to restart after that but it would die if you tried anything but idling it out of neutral.

So I put it on the trailer and got home. Checked fuel pump screen. Checked to see if fuel was "pulsing" but I could not tell if the flow was good enough or not. So next I pulled out the spark plugs. #1,#2 look dirty but ok. #3 had a gray paste on it(fried rings??). I dont have a compression tester at home so i put my finger over the hole and #3 has nothing.

So does anyone have experence rebuilding these? I know I will have to disassemble to inspect the engine block. Hopefully the block isnt too messed up so I can hone out the cylinders and still run standard pistons. Anybody know were to even get oversized pistons if I do need to get the block bored? And any other advice? Should I even rebuild it or say F*#@ the sport jets forever and have a boat burning party????

 

[And-Con]

Re: Blew up the sportjet 90 today!

on a sport jet might as well rebuild; it's not a horribly difficult procedure, just get yourself a good workspace, good manual, and a good set of gloves. Removing the engine from the hull is very simple, find a good tree (I generally opt for oak although I have had some success with mango trees).

The engine should be very similar if not identical to a mercury outboard of the same horsepower. As for pistons, just talk to a local mechanic, he should be able to hook you up with a rebuild kit(gaskets, rings, t-stats, etc.). You most likely can get it cheaper online, but any advice they relay will be worth the difference. It is a 2 stroke, so you can run one cylinder bored and the rest standard if need be.

Or if you prefer glass work,convert it to outboard,seal up jet drive holes, reinforce transom, bolt on bracket. Then send me your steering cable(I'm getting desperate and to get a new one is ending up costing me as much as i paid for the boat )

 

[kend301]

Re: Blew up the sportjet 90 today!

Before you start to overhaul , check a few things , First of all fuel should not pulse it should flow so I would say you need a diaphragm.
Second , pull the head and exhaust manifold , check for scored cylinders and a blown gaskets both head and exhaust manifold.
If you are wondering clean up the cylinder bore , do not clean the gaskets , take some pics and post them up .
If it is indeed toast I have a real good link to complete rebuild kits that I can send you it is like 750.00 for everything including new bearings , any size piston you need .
The other option would be a rebuilt power head , about 1400.00 , have the link for that as well , PM me if you want them.
Also if you decide to scrap the boat , let me know I have someone looking for lots of hard to find and obsolete parts who could help you recoup some money .

 

[dmball]

Re: Blew up the sportjet 90 today!

Im going to take off the head and exhaust manifolds soon and try to get some pics. They have to come off for the engine to come out anyways if need be.
Then I will most likely repair the engine if the damage is not too bad.

 

[dmball]

Re: Blew up the sportjet 90 today!

Removed the head today and found a hole in the side of the piston. So looks like the engine will be comming out sometime soon.

Can you send me those links to those parts kend301?

 

[kend301]

Re: Blew up the sportjet 90 today!

Let me track down the ebay link later today and I will pm you the item number , sellers name and the link to the complete rebuilt powerhead .

See if you can get a better clearer pic , cylinder wall looks good from what I can see , you may get away with just a hone

 

[kend301]

Re: Blew up the sportjet 90 today!

Just sent the info to you

 

[dmball]

Re: Blew up the sportjet 90 today!

Thanks for the links.

I have not removed the engine yet but I did notice today that one of the bolts for the transfer port cover rattled out. Its the cover right next to the cylinder that puked.

Could this cause a lean condition making the piston come apart?
Or should I be looking at carbs/reeds?
I dont know what else could have made the piston come apart.

 

[kend301]

Re: Blew up the sportjet 90 today!

Once you get the engine out we can take a look at everything , it is hard to tell if that is detonation damage on the piston or if it was from a piece of piston rattling around . Post some good clear pics when you get it out and apart we can go form there. I would really go through the carbs on any rebuild . Do a thorough inspection of the reed valves as they could cause a lean condition.

 

[Fed250]

Re: Blew up the sportjet 90 today!

I just ran across a guy who fried his electronics then let his boat sit outside for two years. Its all junked now but the engine is still good and I am pillaging it for parts. I am not taking the block or pistons though. I am sure you could get it for a good price if your interested I can get you the contact info. I am going back this Saturday to take what I need and I can get some pictures if your interested. I bet you could get everything you wanted for only a couple hundred bucks.

 

[kend301]

Re: Blew up the sportjet 90 today!

Cool move here FED , with only 4 posts you are promoted to " It's OK I am with the Band" Status .. nice to see someone help another !!

 

[dmball]

Re: Blew up the sportjet 90 today!

Friday I removed the engine. I was surprised how easy it was. Only had to unhook a few things, then I backed up the boat right to the work bench. Picked up the engine by hand and set on bench. Hope the rest of the project goes this easy.

Been busy all weekend so I have not torn the engine down at all yet. But here are a few pics.(also a couple from the day it blew up)

 

[dmball]

Re: Blew up the sportjet 90 today!

Oh btw thanks for the reply Fed250, pm me and let me know what you come up with.

 

[excalibur1031]

Re: Blew up the sportjet 90 today!

Looks like you have some rocks in the coolant passages. You may want to check to see if you don't have a restriction somewhere. Did the engine overheat?

 

[dmball]

Re: Blew up the sportjet 90 today!

Thats what I was wondering. No alarm ever went off. That passage has a small hole in back. So I think it could deffently have been restricted. But maybe they just got sucked up after I was trying to restart it at the beach after it died.

 

[excalibur1031]

Re: Blew up the sportjet 90 today!

Yeah, just make sure you check all passages in the block and in the boat before putting the engine back. It'd be a shame to go through all that work and end up with the same results. Good luck!

 

[kend301]

Re: Blew up the sportjet 90 today!

That cylinder looks real suspect to being scored to the point it is done ,Hard to tell if that is cylinder wall scoring or just piston muck stuck to it . Keep your options open for a used engine , Pull the motor apart , hone #3 and post some pics . BTW I might have another guy that may wind up with a spare motor in the next few days , I will keep you posted.

 

[dmball]

Re: Blew up the sportjet 90 today!

Well not much of an update yet. Except for I have had the cylinder block bored out .010" and the cylinders look ok. I am going to order a rebuild kit soon.

Problem as of right now though is I do not know why it blew up yet. Only problems I could find is a sticking needle in the #3 carb. I checked #2 and it seems to be sticking too. Oh and by sticking I mean sticking closed. If I blow through the fuel feed I can get it to pop open but it seems to take a bit of pressure. It should move freely correct?

Does anyone think the needle sticking closed while the other two cylinders were running killed #3 by fuel/oil starving it? Like I said I have found nothing else bad in the engine.

 

[kend301]

Re: Blew up the sportjet 90 today!

if you had 2 out of 3 cylinders running lean you will burn a piston , that is exactly what happened to your motor . Rebuild the carbs with new needle and seats and with the engine rebuild you should be fine . Also post pics of the reed valves I am wondering if you should get them too .

 

[dmball]

Re: Blew up the sportjet 90 today!

The reeds look perfect. Besides some metal shavings from the piston. I will try to get a few new pics tomarow.

I also noticed my carb part #'s dont match the ones in the clymer manual. They look just like the picture on page 96 (early modles) but they have part #'s wb119a,120a,121a. Not mentioned in manual.

Also I found the picture #25 on page 99 showing the idle tube location in the main nozzle. My idle tubes come down under the nozzle. But it looks like its pointed in the right direction just maybe too far down. All the carbs are set up this way. I only question this because the "caution" in the book says it will run excessively lean if not installed the same as the diagram.