1994 Boston Whaler Outrage Muffler Heat

[Bilgepump]

Hello All,
My Jetboat is a Boston Whaler Outrage 1994. The motor was overheated a couple of years ago and the boat had sat for about three years. Over the last year I have purchased a short block and have had a mechanic putting it all back together. He is a outboard mechanic and I am comfortable with his abilities. He is not familiar with the jet boat exhaust muffle and we are looking for some guidance. He has the engine running smooth and cool. The muffler is getting smoking hot. He took the muffler off and sent it to a radiator shop to be boiled out. There was no blockage discovered, but they did put hoses to it and the water was crossing over to the dry portion, mixing internally. My questions are as follows:
1. Are these muffles similar to a marine exhaust elbow where the water and gas meet at exit hose connection or are they suppose to mix internally.
2. We still have the mounting plate to test, is there any suggestions as to what we should be looking for ? Thank you in advance for any assistance the team can provide

 

[Julian]

I'm not familiar with that boat/engine, but I would think that one should be able to determine how the exhaust SHOULD work. Yamahas do mix the water with the exhaust, but I've not disected one to see how the water is routed to cool the jacket. I suspect that some sort of baffle has erroded that would normally hold water in the jacket and only allow it to mix in the last section? Does it appear rusted? Can you post some photos?

 

[Scottintexas]

@Bilgepump glad to have you on board, I think your our first Boston Whaler jet!

Unfortunately the general knowledge base doesn't deal with those very often but maybe one of the Sugar Sands guy's can help you out as I think those are very similar engine setups,
@Bilmon @Sugarsand gary - any ideas?

 

[Murf'n'surf]

sounds like the exhaust pressure is greater than the water pressure because of internal corrosion/hole. The water is not being allowed to circulate and causing an overheat of the muffler. I think you need some new parts.

 

[Cobra Jet Steering LLC]

Some confusion here. Are you sure it is not a rage with a 115 hp. O M C jet, the outrage isn't a jet as I recall, those were an outboard thus the name OUT RAGE.
On a jet muffler " water box" you have water going into it to cool it off and create the correct back pressure for the 2 stroke engine to operate properly. You can hear a lot of loud exhaust noise when the water isn't getting in the muffler properly. Some use a vacuume operated valve to adjust the water flow to the water box.

 

[Bilgepump]

I apologize for not seeing these post earlier. I have been involved with other things and not paying attention to the Boston Whaler. Cobra Jet, You are correct, this is a 14' Boston Whaler Rage. with a muffler box as you describe. I found this post I copied below on another site, could this be a condition that would cause the muffler to overheat ?


"Not the water pump. The entire jet assembly is the water pump on a Turbojet. There is no rubber impeller as an Outboard would have. The turbojet uses a hole located at 12 o'clock in the mid-section of the impeller assembly to collect pressurized water for cooling purposes. If you remove the rear funnel portion which compresses the water into a jet (four 6mm allen head bolts), you will find a large flat head screw. Under that screw is a spring and a ball valve. The intent is that the ball valve opens at 20psi to vent excess pressure from the cooling system. However, it is possible to get a piece of debris stuffed into that ball valve and vent the minor pressure available at idle. (I see 0-4psi at idle on my water pressure gauge). It would not take much loss to equal zero cooling water pressure.

I mention this ball valve and the possibility of getting something stuck in it because it is in the portion of the impeller housing you "pull back" to install the OMC garden hose adapter for flushing. Ordinarily, you would never know if it is leaking pressure or not. There is no effective way of testing the valve.

If for some reason, your engine ingested a piece of debris, and that piece of debris was small enough to go into the cooling water pickup hole, it could probably clog something enough to prevent adequate cooling. In theory, everything is supposed to pass through there and get hung up in your strainer, but there is always a possibility you got a Zebra mussel or something odd plugging up the hole. Run water backward through the impeller housing cooling water passage. See if something comes out..."



Thanks for looking

Bilgepump

 

[Cobra Jet Steering LLC]

Damn Alzheimer's I had to go back and read that again to refresh my memory. The post is covering the water supply to the muffler so yes this is something you should check, however as previously stated by Murf, you may also have a problem with the exhaust pressure exiting the water box due to some internal obstruction like sand or a broken baffle or some critter building a nest inside the thing while it was not in use for a period of time. Improper back pressure can hold the water from entering the water box also it can force exhaust gases into the engine cooling passages and contribute to overheating . So I would back flush the water cooling system as described in the post I would remove the thermostat and place it in a pan of water on the stove , heat it to the temp indicated on it and see if it opens as it is supposed to, O M C engines were bad about the thermostats sticking and I would also physically remove the water box "muffler" and be sure it is in good working condition and unclogged. Shake it and see if it rattles, power flush it and look for sand etc. coming out. Also inspect the hoses and clamps while you are at it , Reliability is really important.

 

[Bilgepump]

Thank you for the immediate response. The engine has been completely rebuilt.... Short block, new pistons etc. New thermostats, the whole enchilada !! muffler box was removed and cleaned out at a radiator shop thinking there might be a blockage. Now I am looking for something that I missed , or I need to check the Muffler box again. How can I pressure test that unit ? The Engine does not get hot first, the muffler gets smoking hot than it starts to travel up the lower cylinders and upwards. PS..the engine runs smooth and cool on a hose connection.

 

[Cobra Jet Steering LLC]

First of all normally when an engine like yours is not getting water properly the top cylinders get hot first, you have the opposite situation leading me back to the muffler being the issue. You need to locate the water hose that supplies the water box from the jet pump and check it for obstructions etc. even if you need to pull it off while it is in the water to monitor the water flow for a few seconds.
The other thing to consider is that at idle the water is sufficient to cool the system but at speed it isn't since running on the hose is at low speed.
So Is the system overheating in the water when just idling? If not then it may go back to the muffler being obstructed.

 

[4x15mph]

I had the same overheat condition on my yamaha jet which was a direct result of a clog in my exhaust cooling. water could not circulate in my case.

On my boat, water circulates around the exhaust chamber cooling the exhaust before it enters the water box in the back.

 

[Cobra Jet Steering LLC]

Yea If I recall correctly his is a 4 cylinder outboard block mounted directly to the top of the jet pump but I don't recall all the particulars of that setup. I keep thinking he is having an obstructed exhaust issue . If I recall correctly the water from the pump is sent directly to the power head with no hoses.

 

[Cobra Jet Steering LLC]

I have a question on the rebuild you did. When your mechanic put the engine together did he install the water jacket baffles? I recall some small baffles places in certain locations of the water jacket close to the cylinders , these directed the flow of water around the cylinders to insure it flowed properly, we would actually replace the factory hose style baffles and make some cut from v belts because the original ones would deteriorate and cause the engine to run hot. However if the engine was put together without them it will cause overheating.

 

[Bilgepump]

Cobra Jet, Thank you for giving me so things to discuss with my guy. Let me see what I can find out and I will post what I find out. Really Good intel !!

 

[Cobra Jet Steering LLC]

see the little piece or tube in the center of the water jacket on the right side and another on the bottom right of this picture those redirect the water The original tubes would go bad like the one in the center of this picture so we made them out of v belt to solve the problem some were metal but in any case your motor probably has them.

 

[Cobra Jet Steering LLC]

I think the fitting shown here is where the water enters this muffler, I have no idea what happened to all the other pictures I put on the previous posts.

 

[Bilgepump]

Can someone post the water flow schematic for a 1994 Boston Whaler Rage jet boat. The only one I have located is out of focus and unreadable in sections. Thanks in advance

Phil

 

[Bilgepump]

Good Morning All...Happy 4th of July Weekend !!

Ok further details on my overheating water box. We have found a schematic showing the waterflow and corrected the water flow. The box now is running at 225-240 degrees instead of "Off the chart (400 +)". Is this a acceptable "Muffler box Temp "?

Now a new situation has developed. I installed a regular outboard fuel pump on the engine, not thinking about it actually being a inboard. I have the old VRO pump and housing, can this be rebuilt and if so any recommendations as to where to send and what I should spend.

Now that I have tested the Boston Whaler Rage Jetboat...I am hooked, what a rocket!! Now I just need to work out some minor bugs and go BOATING !!

Thanks All
Phil
PS. I have dragged the boat up to the Greeneville, Tn. area

 

[rockb]

How are you liking the Rage? Considering a 19 15'

 

[Cobra Jet Steering LLC]

Damn I am getting old I wonder why I never said anything about getting rid of the stupid push pull fuel pump and replacing it with a 3.5 lb electric pump I use those all the time in place of the originals on 2 stroke engines and they work so much better than the vacuum operated ones and keep the engine at a steady rpm with no fluctuation and you prime the engine simply by turning on the key and waiting a few seconds Haaa soon people will be saying 2 stroke ??? what the hell is that????.