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  1. #1
    Join Date
    Jul 2007
    Location
    , NJ, US
    Posts
    67

    Default Where to mount thru hull for cooling water intake?

    Thanks in advance for you thoughts and help

    I am seeming to have a problem with my 7.4l Bravo1 drive getting enough raw water to cool the engine at speed (link to other thread) http://www.marineengine.com/boat-forum/showthread.php?391655-Problems-with-rebuilt-7.4-running-poorly-and-valve-taps-HELP!!-Update

    My question is if the attempt to clear up the clog in the system does not work out as planned (the transom assy is from 89 so it could be corroded up pretty good and not be repairable as some have told me) and I am forced to choose between a new transom assy or a thru hull intake just where would be the best place to install the fitting at?

    I have read about being sure it is towards the transom, not in a strake or stringer etc and that all seems pretty straight forward, but also leaves a lot of real estate to choose from.

    Below is a picture of the bilge on the side of the engine where the raw water pump is mounted as I am guessing this would be the best side to use due to the pump etc.

    Now just where to put it is puzzling me a bit, and I am truly concerned with creating more work from getting to close to a stringer or? Should it center between from the stringer, closest to the transom that allows operation of the valve, or is that totally wrong?

    Also can anyone confirm that this is fiberglass only and that there is no wood used in that area (89 SR 260cc)?

    Click image for larger version. 

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    Last edited by lennyd; 07-17-2011 at 02:34 PM.

  2. #2
    Join Date
    Jul 2007
    Location
    , NJ, US
    Posts
    67

    Default Re: Where to mount thru hull for cooling water intake?

    I guess I am not the only one who is not familiar with the lay up on this boat

  3. #3
    Join Date
    Aug 2006
    Location
    SW Ohio, USA
    Posts
    10,277

    Default Re: Where to mount thru hull for cooling water intake?

    Call the boat manufacturer and ask them about the hull construction. You could go visit a boat dealership, talk w/the shop manager and have a look/see where some of the thru hull water intakes are located on new/old boats and take some pics. and measurements.

  4. #4

    Default Re: Where to mount thru hull for cooling water intake?

    Quote Originally Posted by lennyd View Post
    I guess I am not the only one who is not familiar with the lay up on this boat
    Mercruiser actually had supplied a transom mounted raw water pickups for some of the HiPo engine setups. I think I would prefer that over hogging a big hole into the bottom of the boat. There are lots of articles about the different setups available on the net.

  5. #5
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    6,956

    Default Re: Where to mount thru hull for cooling water intake?

    Food for thought!

    The Merc A drive requires that the lower unit sea water pump (and path) remain active for upper unit cooling...., even while doing a direct thru-hull pick up system. As the sea water passes through the upper housing, it removes an amount of heat.
    I don't know about the B drives, but you may want to consider this prior to completely circumventing this sea water path.
    Or add a shower.

    As for cutting a hole for a thru-hull fitting...... have no fears.
    Many of us have thru-hulls...... seacocks for head water, generator cooling, wash down pumps, True "Thru-Hull" transducers, etc.
    Do as the pros do, secure it and seal it well, and you should have no problems.

    .
    Rick ... aka Ricardo
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

  6. #6
    Join Date
    Jul 2007
    Location
    , NJ, US
    Posts
    67

    Default Re: Where to mount thru hull for cooling water intake?

    Quote Originally Posted by guyjg View Post
    Call the boat manufacturer and ask them about the hull construction. You could go visit a boat dealership, talk w/the shop manager and have a look/see where some of the thru hull water intakes are located on new/old boats and take some pics. and measurements.
    Had thought of talking with SeaRay, but have not had positive outcomes from doing that in the past as I usually have received conflicting info from them.

    I don't believe this model ever came with a true inboard, and I have not seen one with a through hull.

  7. #7
    Join Date
    Jul 2007
    Location
    , NJ, US
    Posts
    67

    Default Re: Where to mount thru hull for cooling water intake?

    Quote Originally Posted by 04fxdwgi View Post
    Mercruiser actually had supplied a transom mounted raw water pickups for some of the HiPo engine setups. I think I would prefer that over hogging a big hole into the bottom of the boat. There are lots of articles about the different setups available on the net.
    I had originally thought of this route, and parts should be available as it is the same as used on the TRS drives, But the idea of messing around with a 22 yr old transom scares me to death. This company does not have the best track record with sealing the wood areas, and I do not want this to progress into a serious rebuild etc.

  8. #8

    Default Re: Where to mount thru hull for cooling water intake?

    Quote Originally Posted by RicardoMarine View Post
    Food for thought!

    The Merc A drive requires that the lower unit sea water pump (and path) remain active for upper unit cooling...., even while doing a direct thru-hull pick up system. As the sea water passes through the upper housing, it removes an amount of heat.
    I don't know about the B drives, but you may want to consider this prior to completely circumventing this sea water path.
    Or add a shower.

    As for cutting a hole for a thru-hull fitting...... have no fears.
    Many of us have thru-hulls...... seacocks for head water, generator cooling, wash down pumps, True "Thru-Hull" transducers, etc.
    Do as the pros do, secure it and seal it well, and you should have no problems.

    .
    I was actually more concerned about loading / unloading from trailer and possible damage to the pickup of a bottom mounted intake.
    Trailered boats present thier own set of problems.

    FYI..... Never considered doing away with the drive pickup on my boat, especially considering your "what if's". Just tried kicking in some alternetive suggestions to the OP's questions.

  9. #9
    Join Date
    Jul 2007
    Location
    , NJ, US
    Posts
    67

    Default Re: Where to mount thru hull for cooling water intake?

    Quote Originally Posted by RicardoMarine View Post
    Food for thought!

    The Merc A drive requires that the lower unit sea water pump (and path) remain active for upper unit cooling...., even while doing a direct thru-hull pick up system. As the sea water passes through the upper housing, it removes an amount of heat.
    I don't know about the B drives, but you may want to consider this prior to completely circumventing this sea water path.
    Or add a shower.

    As for cutting a hole for a thru-hull fitting...... have no fears.
    Many of us have thru-hulls...... seacocks for head water, generator cooling, wash down pumps, True "Thru-Hull" transducers, etc.
    Do as the pros do, secure it and seal it well, and you should have no problems.

    .
    I had discussed the issue of cooling water through the drive with a local tech, and it seems it would be a good idea to keep it flowing through there etc. I am thinking to leave it operative (even though at a reduced flow) by utilizing a T fitting and let the system still take water from the drive as well.

    I do not fear the idea of the hole so much as I am confident modern epoxies will hold up well etc, but my fear is all the talk I have seen about these guys coring their hulls with balsa, and just what taking a hole saw to it could open up etc. I do not believe they did this is the bottom on the smaller boats, and it was more of a cost cutting design on the hull sides on the larger ones, but it just seems I can not confirm this one way or the other.

    Since I just watched a guy on Iboats/you tube completely remove and replace everything below deck on a newer 240 bowrider I am nervous as hell lol.

    I dont have any signs of problems etc, but I also want to keep it that way.

  10. #10
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    6,956

    Default Re: Where to mount thru hull for cooling water intake?

    Quote Originally Posted by 04fxdwgi View Post
    I was actually more concerned about loading / unloading from trailer and possible damage to the pickup of a bottom mounted intake.
    Trailered boats present thier own set of problems.
    Good point!
    I trailer my 28 SDN F/B and this was considered when locating penetrations.
    This should not be an issue if you plan and layout for the bunks/rollers, etc., just as you would for most any installation.

    Layout, layout, and then more layout..... then make your cut!
    Rick ... aka Ricardo
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

  11. #11
    Join Date
    Oct 2009
    Location
    archer city, texas, us
    Posts
    186

    Default Re: Where to mount thru hull for cooling water intake?

    i would put a drive shower on any way you cant get enough coolant,it helps outdrive bearings too!!! you can get one on e-bay around 100.00 i did takes about 15 mins to put on. good luck

  12. #12
    Join Date
    Jul 2007
    Location
    , NJ, US
    Posts
    67

    Default Re: Where to mount thru hull for cooling water intake?

    Quote Originally Posted by mikey43 View Post
    i would put a drive shower on any way you cant get enough coolant,it helps outdrive bearings too!!! you can get one on e-bay around 100.00 i did takes about 15 mins to put on. good luck
    After much debate (both with marine minded friends, marine mechanics, and even myself lol) I have decided 100% to go with the through hull fitting. I purchased all the Groco parts from the seacock to the pick up etc, made two different wooden backing plates, have all the sealant and hole saws etc.

    It was a real pain trying to figure out the best location to mount this for sure. I really wanted it to be as close to center line as possible, but also accessible and in a position that would make sense for feeding the pump etc. Then of course I wanted to be sure not to install behind a lifting strake or other obstruction etc.

    I think I have finally decided on a location. It is just outside the main stringer that supports the engine, and more than halfway towards the center on the starboard side. It looks like it will also clear the rollers of the trailer etc (one of the haulers I use has a roller trailer, and I do borrow one from a neighbor at times as well). It will be outside of the area of the bilge under the engine and almost inline with the routing of the previous path of the hose coming in from the transom leading to the engine mounted pump.

    Did I cover all the needed concerns?

    Only thing I have left to decide on is what to do with the hose from the drive to the transom (the one that was making all the problems in the first place) and I am not sure on this as the idea of the intake water cooling the drive does make sense, but much as I like the idea of leaving it all in place and just adding it to the system with a tee fitting or similar I am concerned due to the facts that it was corroding and closing itself etc, and the attempt to open it with a drill may have left a hole that could cause the whole system to suck air etc. which does not cool well.

    Would it be better to just cut that hose on the outside of the hull and block it off on the inside? It should still allow water to flow up through the drive as it would likely be forced by moving though the water etc, but could there be any problems from allowing that same flow to just be hitting the outside area of the gimbal or transom housing?

    I figured the same area is under water most all the time anyway so it should not be a concern, but really wanted to hear what others thought too.

    Since most everything else is ready to go (minus bottom paint as that is waiting until the through hull in finished) this is the last thing holding up launching.

  13. #13
    Join Date
    Aug 2008
    Location
    Jamesport, New York, United States
    Posts
    176

    Default Re: Where to mount thru hull for cooling water intake?

    Lenny, You really should add the Drive Shower. At speed the top of the drive is out of the water. Heat is the enemy of oils and metals. Drive Showers help keep cooling water on the upper Gears and Bearings. When I converted my B-III to a thru hull, I bought a Sea Scoop that actually catch"s water when you run at speed and force feeds the pump. As for the old cooling port, Mercruiser makes a block off plate for the Bravo III which may be the same for a B-I. Let us know how you make out. BTW, 3M 5200 used as a sealing agent is a must when you install your Thru Hull.

  14. #14
    Join Date
    Jul 2007
    Location
    , NJ, US
    Posts
    67

    Default Re: Where to mount thru hull for cooling water intake?

    Quote Originally Posted by wickeral View Post
    Lenny, You really should add the Drive Shower. At speed the top of the drive is out of the water. Heat is the enemy of oils and metals. Drive Showers help keep cooling water on the upper Gears and Bearings. When I converted my B-III to a thru hull, I bought a Sea Scoop that actually catch"s water when you run at speed and force feeds the pump. As for the old cooling port, Mercruiser makes a block off plate for the Bravo III which may be the same for a B-I. Let us know how you make out. BTW, 3M 5200 used as a sealing agent is a must when you install your Thru Hull.
    Thanks for the info!

    I am seriously looking at the drive shower idea, or some way to keep the drive cool or at least not get any hotter than before. One thing I am considering is just cutting the original hose outside the boat and let the boat moving through the water just push sea water up through the drive and out the hose etc. If anyone has any input on this I would be appreciative and if it is first hand experience more the better etc.

    I am going to be honest that I am a bit confused on all the info both for and against using 5200, and for now at least am glad I
    went with 4200 (as many have suggested all over the net) since I may actually need to pull it apart which I will explain below. I °am a fan of 5200 and have used it in many other areas (some I hope never to regret or have to remove lol) but after reading about various opinions on 4200 being suitable for below the water line and all the problems other have faced trying to remove the 5200 I did ultimately opt for the 4200.

    I did run into a problem during my "dry fit" as the 20x I measured everything went to poop when somehow the angle of the hull caused the peacock to be just a tad (I am talking factions here) too close to the stringer and I was not able to continue to turn the sea cock fully tight and had to improvise by turning the pick up tight as possible and then turning the sea cock an additional 1/3 turn to tighten the balance of the way.

    It was just hitting the stringer as it got lower, and I even doubled up my backing plate to try and raise it. It is tight, but not as tight as I would prefer being it is covering a hole in the bottom of my boat. On the other hand I can over tighten things lol, have enough sealant and epoxy in this set up it may have added 3lb to the weight of the boat, and well I may just be a bit concerned because there is a hole in the bottom of my boat lol.

    I did test it best I could on land by flooding the area it is mounted up to the bottom of the elbow and it did not leak a drop so maybe it is fine and I am just overly concerned etc.

    What was happening is that in order for it to be totally tight either the handle had to be inoperable from being pushed into the stringer or the pick up had to be facing backwards. So it is currently less than 1/2 turn from what I liked or considered fully tight, but again I may have wanted it tighter than it needs or should be (I have thought that fully tight would push out all he sealant between the mating parts etc) .

    It has three bilge pumps and I am going to wire in a new warning buzzer just in case, but if it should leak I think I will be happy I went with 4200 because I will need to remove the pick up, the sea cock or both to use a different set up and that would stink with 5200.

    Any thoughts on if it does leak if I would be better switching the sea cock to the separate base and valve offered by groco, use a STD pick up with a separate hi speed pick up grate, or something else? I was even thinking of looking for a different way to attach the hose to the sea cock that would clear the stringer or just route differently or even just reducing the height of the backing plate to hopefully change the amount of turns needed so that everything would line up and tighten better.

    If it wasn't for the fact I know I want another 1/3-1/2 turn it looks fine, and I wouldn't question anything if I had had a yard do the job and it came back like it is. Maybe I am just being "anal" or too concerned etc.

    I remember seeing the block off plate somewhere and was going to plug the hose I will have left over and attach it to the original spot until I find one.

    I have a few other repairs left to cover before launching, but was anticipating some time next week so there is still time for some changes etc.

    Thanks!

  15. #15
    Join Date
    Jul 2007
    Location
    , NJ, US
    Posts
    67

    Default Re: Where to mount thru hull for cooling water intake?

    Forgot to put in the above reply.

    Tell me more about the scoop you put on the BIII.

    Is it different than the scoop strainers made by Groco and Atwood etc?

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