Overheating/Bigblocks

[SteveG]

I have an 89 wellcraft Nova Spyder twin 454/330's with 400 hrs on the motors and the starboard motor is over heating. Bravo outdrives/ no pump in the lower unit. When I start them the one it always rises to tempature faster than the other and it is by 10 deg while ideling. When I plane off and run the temp difference is by 40 deg, as soon as I come off plane the motor temp drops in about 5 minutes. The alarm system never sounds and it has been up above 200 deg. I have replaced the impellar, replaced the thermostat, cleaned the risers, changed the temp sending unit, swapped the gauges on the panel and still can not figure out the problem. I have flip flopped the thermostats and sending units, no luck. I have pulled hoses to see if the pump is pulling water and the flow looks good. I have no clue on what to do next, I have the mechanical ability to fix it myself if I knew what the problem is. Experience and knowledge required from someone that has dealt with this problem, thanks!

 

[12Footer]

Re: Overheating/Bigblocks

Hi, Steve.<br /> Check the intake for livestock or other obstruction. It may be open,but not open enough to draw a full flow. Also,make sure the hull before the the intake is free of deflections,barnacles or anything that would make the intake grab air-rich water.<br />If yours is closed cooling circuit, I do not know how to help ya.<br />(Never fiddled with one).

 

[pinkmouse]

Re: Overheating/Bigblocks

one problem that happens is the water tube in the transom houseing has a plastic bushing that if you use your boat in salt,the bushing colapses over time restricting flow

 

[hondon]

Re: Overheating/Bigblocks

You mention they are bravos, but are they set up counterrotational?

 

[Walter]

Re: Overheating/Bigblocks

My word...what HAVEN'T you tried?? I'VE no clue what could be causing this...Let me confer with my local Merc hotrod Baja rep and see if he's ever heard of such a thing. Unless it's something prohibiting the starboard outdrive from sucking up her share of water...closed cooling or not....I can't offer anything that you haven't already tried.<br /><br />Each engine's cooling system is entirely independant of one another, isn't that correct? If so, then either your starboard engine is being starved of it's normal cooling ability or is somehow creating more heat that it's cooling system is designed to disperse. <br /><br />What about her recent history? Have you owned this lady for a while or have you recently purchased her? Has she had any recent work done to the starboar engine?? If so, might that have anything to do with what you are now dealing with?<br /><br />I'd be very interested to know what finally fixes your problem....keep us informed Steve!<br /><br />Walt

 

[Fouled Plug]

Re: Overheating/Bigblocks

When was the last time the heat exchangers were cleaned? May have restricted flow in one and not the other. Assuming you have fresh water cooling, that is. <br /><br />------------------<br />I'm going to invent a TCW3/citronella oil blend and make a fortune!