Rage Jet Drive Cooling Modification

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
fandango
Posts: 2
Joined: Sat Jul 29, 2017 4:04 pm

Rage Jet Drive Cooling Modification

Postby fandango » Sat Jul 07, 2018 11:42 am

I am the original owner of a 1995 15-foot Rage with the OMC 115-HP engine. After a number of years of dry storage I have been recommissioning our boat. I pulled the engine and jet outdrive unit and cleaned them up. The engine is running and the outdrive is working.

The original design of the cooling has the jet drive impeller shoot water into an orifice which then makes a 180-degree turn to be feed back through the transom and after going through a filter it is feed into the engine casting for cooling -- this design seems as if it might be a weak point in keeping the engine adequately cooled.

Has anyone modified the design to alternatively install an electric pump pulling water through a thru hull fitting (possibly the drain plug) with a regulator to keep the water pressure under the 20 psi max -- thereby assuring that you are getting full water flow into the engine?

The reason for this enquiry is that I wonder if the complicated original design has historically caused overheating in these Rage engines?

Thanks,

Bob

Fishman
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Joined: Wed Dec 05, 2018 1:03 am

Re: Rage Jet Drive Cooling Modification

Postby Fishman » Wed Dec 05, 2018 2:02 am

I've never seen [a Boston Whaler RAGE] boat, but I am interested in getting one. [I] hope there is a modification that can address the concern about water flow.

The ideo to use an electric pump is interesting. What kind of pump you would use?

I think a 12-Volt electric pump able to put out 20-PSI with enough water volume would use too much current and run continually.

How much water do you think [a Boston Whaler RAGE boat cooled by an electric water pump] would need?

Older post offer four theories for the cause of poor water flow and overheating:

--intake orifice clogging
--a ball and spring pressure relief valve clogging
--thermostats restricting flow; remedy is remove thermostat and poppet valve
--and 180-turn restriction

At the least think I would put on an advanced strainer of some kind, a water pressure gauge, and alarm.. A pressure sensor and alarm would seem to me to be better than the only a head temperture sensor.

Yellowjacket
Posts: 24
Joined: Mon Jul 31, 2017 9:33 am

Re: Rage Jet Drive Cooling Modification

Postby Yellowjacket » Thu Dec 06, 2018 7:05 pm

Waterjets make a ton of pressure, at high power it's over 50 psi in the area where this is tapped into. The worst case is actually at idle, where there isn't a lot of pressure, but there should be enough to pump water up to a level above the head, and so long as the thermostat is open and it isn't clogged and the system isn't clogged you've probably got plenty of water and pressure.

The key concern here is making sure you don't suck up a lot of mud and clog up the inlet or get junk into the cooling system. Obviously, if you have a filter in the system, and it clogs you're going to be in trouble, so it may just be a matter of maintenance in that if you aren't paying attention to the filter you can loose cooling flow and that ends the game.

An electric pump isn't going to put out more pressure than the waterjet when the engine has high cooling demand. Tapping the waterjet for cooling is used on tons of jetski's so there isn't anything really wrong with the idea.

Fishman
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Joined: Wed Dec 05, 2018 1:03 am

Re: Rage Jet Drive Cooling Modification

Postby Fishman » Sun Dec 09, 2018 8:19 pm

Thank you for the information.

jimh
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Location: Michigan, Lower Peninsula
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Re: Rage Jet Drive Cooling Modification

Postby jimh » Mon Dec 10, 2018 8:30 am

Fishman wrote:...A pressure sensor and alarm would seem to me to be better...


The water pressure in the engine cooling system will vary over a wide range of pressure with engine speed. How will you configure the alarm system to detect a problem with water pressure when the desired water pressure is so dependent on engine speed? Please describe your plan.

If an alarm is going to alert when there is a problem, the alarm system will have to know the expected minimum water pressure for each engine speed range. If the alarm system has only one pressure sensor alarm threshold, say for the lowest pressure expected at engine idle speed, then that system would never detect a problem in the cooling water pressure at higher engine speeds. I am interested to know how you plan to solve this problem for your alarm system that detects problems in water cooling pressure.

dtmackey
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Joined: Thu Sep 28, 2017 9:29 pm

Re: Rage Jet Drive Cooling Modification

Postby dtmackey » Tue Dec 11, 2018 11:06 pm

My son has a Waverunner with an engine that has close to the same power as your Whaler. Never has it had a problem with an overtemp condition, but it also does not have poppet valves or a thermostat. The water runs freely to cool the motor. Rather than complicate a simple 2 stroke motor, I'd look into removing the restrictions (poppet and t-stats) and buy a cheap IR temp gun at Harbor Freight to confirm temps.

D-