Modified Water Inlets on Twin Mercury Outboards

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Author Topic:   Modified Water Inlets on Twin Mercury Outboards

Royce posted 03-27-2003 11:59 AM ET (US)
I have twin mercury 150 efi (1999). They have stainless steel plates screwed over the water inlets which allow about a 1/8" opening on the front end of the plate. The plates are labled rt top and lft top. Have any of you motor experts seen these before? This boat was from Florida--could they have been put on to prevent weeds from being sucked in? Should I take them off? Thanks--Royce
Bigshot posted 03-27-2003 01:28 PM ET (US)
They are there to guide water into the bottom of the oplates only. Usually for a raised engine on a jackplate so the pump does not "suck air". If you remove them you will need to replace with stoock grates....no biggie.
Royce posted 03-27-2003 08:19 PM ET (US)
Bigshot- thank you. In fact these are on a 1985 25ft. outrage Cuddy that was recently repowered using jackplates (because the motors have 25" shafts). I called a number of the Mercury dealers in the SF Bay area- they all acted like I had been smoking something. I tried to remove the plates and found the screws to be quite in place. I would just as soon leave them as long as they are not harming anything. Are these a Florida invention?
Royce
kglinz posted 03-27-2003 09:04 PM ET (US)
I saw them, in Canada, on a 225 Opti used as a single on a 23 Conquest. The owner had a overheating problem and said the plates cured the it.
Clark Roberts posted 03-28-2003 06:53 AM ET (US)
Royce, the water intake consists of eight round holes (tapered to forward so water just slides in aided by forward motion of boat) on each side of lower unit... no grates at all! From your description I would say that these added pieces are intended to direct the water more positively into these intake holes especially at speed when the thermostat bypass is open for max cooling at high rpm. I have seen homemade devices of metal and plastic to accomplish same. I assume that they are easily removable (with screws?) so that they can be cleared of debris/mud etc. if clogging occurs.... Happy Whalin'.. Clark
Clark Roberts posted 03-28-2003 06:57 AM ET (US)
just re-read your post and you said they are screwed in place and screws are frozen... suggest you leave in place and flush out to make sure no clogging...
jimh posted 03-28-2003 09:18 AM ET (US)
This article discusses such a modification:
http://www.stvowners.com/hi_performance_handling.htm
See the section "Special Multiple Engine Considerations On V-Bottom Boats"
jimh posted 03-28-2003 09:21 AM ET (US)
[Changed TOPIC; was "mercury (sic) outboard help"--jimh]
Royce posted 03-28-2003 02:25 PM ET (US)
Thank you- an interesting link. My guess is that these plates were installed for a good reason and I am going to leave them on until I hear a compelling reason to remove them.

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Author	Topic: Modified Water Inlets on Twin Mercury Outboards
Royce	posted 03-27-2003 11:59 AM ET (US) I have twin mercury 150 efi (1999). They have stainless steel plates screwed over the water inlets which allow about a 1/8" opening on the front end of the plate. The plates are labled rt top and lft top. Have any of you motor experts seen these before? This boat was from Florida--could they have been put on to prevent weeds from being sucked in? Should I take them off? Thanks--Royce
Bigshot	posted 03-27-2003 01:28 PM ET (US) They are there to guide water into the bottom of the oplates only. Usually for a raised engine on a jackplate so the pump does not "suck air". If you remove them you will need to replace with stoock grates....no biggie.
Royce	posted 03-27-2003 08:19 PM ET (US) Bigshot- thank you. In fact these are on a 1985 25ft. outrage Cuddy that was recently repowered using jackplates (because the motors have 25" shafts). I called a number of the Mercury dealers in the SF Bay area- they all acted like I had been smoking something. I tried to remove the plates and found the screws to be quite in place. I would just as soon leave them as long as they are not harming anything. Are these a Florida invention? Royce
kglinz	posted 03-27-2003 09:04 PM ET (US) I saw them, in Canada, on a 225 Opti used as a single on a 23 Conquest. The owner had a overheating problem and said the plates cured the it.
Clark Roberts	posted 03-28-2003 06:53 AM ET (US) Royce, the water intake consists of eight round holes (tapered to forward so water just slides in aided by forward motion of boat) on each side of lower unit... no grates at all! From your description I would say that these added pieces are intended to direct the water more positively into these intake holes especially at speed when the thermostat bypass is open for max cooling at high rpm. I have seen homemade devices of metal and plastic to accomplish same. I assume that they are easily removable (with screws?) so that they can be cleared of debris/mud etc. if clogging occurs.... Happy Whalin'.. Clark
Clark Roberts	posted 03-28-2003 06:57 AM ET (US) just re-read your post and you said they are screwed in place and screws are frozen... suggest you leave in place and flush out to make sure no clogging...
jimh	posted 03-28-2003 09:18 AM ET (US) This article discusses such a modification: http://www.stvowners.com/hi_performance_handling.htm See the section "Special Multiple Engine Considerations On V-Bottom Boats"
jimh	posted 03-28-2003 09:21 AM ET (US) [Changed TOPIC; was "mercury (sic) outboard help"--jimh]
Royce	posted 03-28-2003 02:25 PM ET (US) Thank you- an interesting link. My guess is that these plates were installed for a good reason and I am going to leave them on until I hear a compelling reason to remove them.