Overheating SportJet 90

[kenimpzoom]

Since last season my Sport Jet 90 would overheat (alarm goes off) after about 5 minutes at idle. The engine runs quite hot (can only keep hand on head for about 1 second) even when going fast. It overheats both with the thermostat in and out. I have taken the exhaust manifold off and checked for clogs and there is none. I ran water all through the engine and water easily flows.

I have traced it down to the water supply. I can run it on the water hose for hours and it never gets hot. I have to choke down the water hose to nearly shut before it even starts to get hot. So I am confident it is a water supply issue.

On the sport jet 90, the water is supplied from the propulsion jet. There is a little port in the jet that leads to a hose and that hose is run to the cooling inlet on the motor.

When at idle (in the water), I can remove the jet to engine hose and put my finger over the pump outlet and there is water coming out, but there is virtually no pressure. I can easly hold back the water with one finger. Even increasing the throttle, I can still easily hold back the water.

So I believe I am getting volume, but no pressure.

Has anyone ever run into an issue where the jet wont produce cooling water properly?

Thanks,

Ken

 

[Zamboni]

Re: Overheating SportJet 90

Hey Ken-good to see your still around, I've sent a few people to your ignition page.

Sounds like you've eliminated the obvious-any type of blockage/restriction. I would still look a liitle further into that, your certain flow is good from the 90* brass fitting where your tapping into the cooling system forward....did you check from pump to floor fitting?

Try connecting your city water hose to the floor fitting and flush backwards into the pump-possibly there is a restriction there. Doesn't take much to cause a problem with SJ cooling system-I pulled a pebble from a wear ring orifice causing same problem your having-jammed in there tight and blocking 1/2 hole....just out of sight. For 2 years that guy had to rev in no wake zones and not idle.

The wear ring housing has an o-ring where that water connects to pump assembly, if no blockage found check that.

 

[kenimpzoom]

Re: Overheating SportJet 90

Thanks for the ideas Zamboni keep em coming.

I have taken out the wear ring and checked all passages for blockage and found nothing. But I am definatley going to double check it.

I thought I had it licked when I used JB weld to build up my wear ring. I thought it was so worn out it wouldnt pump properly. Now I can accelerate faster, but still overheats.

I wont let it beat me!!!!

Ken

 

[JUSTINTIME]

Re: Overheating SportJet 90

does it over heat on the hose at the house?

 

[Zamboni]

Re: Overheating SportJet 90

Original thread says he can run for hours on hose at home without overheating. Doesn't seem to be too low an idle either as the engine is hot after "going fast"

I'm not sure what to try next Ken, it doesn't take much to affect this cooling system-little margin for error. There's nothing to break or wear out but it is prone to blockages. Your city water supply(hose) is much higher pressure than the pump generates so that can overcome restrictions-that fools some people but you pulled exhaust manifold off and checked for sand packed in there.

Still thinking something btw the 90* fitting at floor(where hose attaches) and the wear ring pump intake hole. Can you jerry rig fittings and connect your city water supply hose there-reverse flush. Be good to eliminate a restriction there....and check for a leak.

Pumps I 'lined' for tight impellor fit resulted in the engines running cooler-better water pressure from the pump loading up.

 

[JUSTINTIME]

Re: Overheating SportJet 90

your problem is in the pump side then

 

[kenimpzoom]

Re: Overheating SportJet 90

I have previously pumped water through the brass fiting and out the back of the boat. Water sprayed everywhere, but I am determined to get that brass elbow off and get a better look. I nearly broke my arm trying to get it off, gonna have to get more leverage, but not much room in there to operate.

I have run some 14 gauge electrical wire through the passage way, but I can't get it to make it all the way. Not sure if that is because something is in there, or because of all the bends.

Oh fun, fun, fun!

Ken

 

[Zamboni]

Re: Overheating SportJet 90

Could just be the bends binding the wire, getting that first 90* fitting off will let you know.

There is still possibility of restriction from the fitting forward into the engine-your city water supply is far higher pressure than the pump so may be overcoming the restriction to cool the engine on the hose. Hoping you find a stone lodged just up from wear ring-talking with a buddy about this he's seen it also.....zebra mussel in that case.

 

[Rob454]

Re: Overheating SportJet 90

Take the inlety hose off at the motor and spray water down the hose. Backflush the cooling supply hose. you should have a steady stream of water coming out of the pump. Most likely you have a pebble stuck somewhere in the cooling line. Sand tends to do that and it collects in nooks. As for the water pressure at idle you wont have much pressure and you should be able to stop it with your thumb as you increase speed you shouldnt be able to do that.
Rob

 

[hotrodjet]

Re: Overheating SportJet 90

I have the same problem with one of my boats.It is the sportjet 90 also. I took the plastic plug out of the top of the motor,the one right above #1 spark plug. I put a barbed fitting in it and ran a hose over to the outlet hose of my bilge pump.It will still overheat sometimes but i can view the hose and give the boat more or less throttle to get the water to flow through the hose and cool boat back down. Did you figure out your overheating problem? I have good flow comeing out of the 90 degree fitting.

 

[Gravel Grinder]

Re: Overheating SportJet 90

I have the same problem with overheating. I was able to get the brass fitting off by using an abrasive blade in a small angle grinder to cut the bolt off above the nut and using the same blade to grind off the bottom of the brass threads that would still hit on the nut. Then I could unscrew the fitting. After getting the brass fitting off, I still didn't have any blockage in the hose or brass elbow. I then took off the exhaust manifold and found it clean in there. So... has anyone found any blockage anywhere else???

Thanks

 

[kenimpzoom]

Re: Overheating SportJet 90

After all the rain delays and other things I finally got the elbow off. I used vise grips and tied a rope to them and had my son pull hard while I hit the vise grips with a hammer. It finally broke free and I spun it around.

But, I didnt find ANYTHING. I sprayed with the water hose and no blockage found. Ran a 14 gauge wire thru there and it passed just fine.

I havent had a chance to test ride it, but I still see no reason why it is fixed.

Next option is either a new wear ring, or run an inline water pump. I have an old Holley fuel pump that I will try.

Ken

 

[kenimpzoom]

Re: Overheating SportJet 90

Fixed!

It was one of two things:

1) The passages thru the jet drive were blocked and I unplugged them after the elbo removal (see above post)

2) I felt like the engine was idiling too low. I found out the idle stop screw was not even touching the block. This made the cam engagement be very late. Had I read the manual, I would have spotted this a long time ago. I adjusted the idle stop screw as described in the manual, except I dont have a tach. I just slightly bumped up the idle.

Now no more over heating. I can keep my hand on the exhaust manifold for 10 seconds, and my palm can sit on the head for about 2 seconds. Before, I could hold each for about half a second before it would hurt.

Man, its good to be back running!!!!!

Now I gotta fix all the other junk!

P.S. My wife caught a 20 inch Red drum last night in the boat, she was soooooo happy.

Ken

 

[Zamboni]

Re: Overheating SportJet 90

That's great Ken-still lots of summer to enjoy the boat.