Installation of a "through hull" to cool engine

Jamey Diggs

Member
Jul 15, 2018
44
Merritt Island, FL
Boat Info
270 Sundancer 1999
Engines
5.7 Mercruiser 250HP
Transomcleaned.jpg
I have a 99 270 Sundancer. After two mechanics and a lot of $$ he took the outdrive off to discover the transom assy was basically deteriorated. I was having major overheat issues and it was clear that the transom assy bushing had basically closed off the artery where water should be flowing in. When they tried to clean it out and install a new hose, the housing of the assembly was so deteriorated that it wouldn't properly "house" and stabilize the hose (thus requiring a new $3000 transom assy). He is recommending that instead of buying that I can have a "through hull" installed much cheaper to cool the engine. Any thoughts here? I'm concerned that if I get in sand or shallow water the debris will suck into my engine and ruin it. I run in some shallow rivers often in Cape Canaveral. I bought the boat for $15K knowing I'd have to put some $ in it, but I've now doubled that in repairs and now I'm here. Should I put the "through hull" in or replace the transom assy? Thanks
TransombushSeaRay99.jpg
 
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Just went thru the same thing on my 240 sundeck in florida. I opted for new new transom assm. as well as a new starter and bilge pump (had the engine out anyway) new raw water pump, and elbows. My engine is full closed cooled and I flush it after every trip so I figure I good for a while now.
 
I did a lot of research on this as I was going to due this on my boat, goggle capping off water intake in drive.
The main problem that I see is the water cools the drive as it goes though it, if it is capped off will the drive overheat.
They say if you do this to install shower drives on the lower unit, When you plain off the drive comes out of the water and the shower drives spray water on top of the drives to cool it (10 degrees ).
My boat came with the shower drives from the factory so I never did it.
 
Just went thru the same thing on my 240 sundeck in florida. I opted for new new transom assm. as well as a new starter and bilge pump (had the engine out anyway) new raw water pump, and elbows. My engine is full closed cooled and I flush it after every trip so I figure I good for a while now.
Yes I've changed all the pumps, starter, elbows so that is all good. I'm just trying to avoid the new transom assy if the through hull will serve the purpose. Thanks for reply!
 
you are actually way less likely to suck up sand usung a thru hull and you use a strainer too- i converted my boat over - no need for a drive shower if you remove or cut a section out of the hose in question (from the drive to the transom assy) this way it still gets flow thru cooling - my boat has been like this for 10 yrs - kept my boat at harbortown on the barge canal for a couple years and polished the props plenty trying to get closer to ski island.....just make sure you dont let anyone flush the boat thru the drives (just put a hose in the strainer)
 
you are actually way less likely to suck up sand usung a thru hull and you use a strainer too- i converted my boat over - no need for a drive shower if you remove or cut a section out of the hose in question (from the drive to the transom assy) this way it still gets flow thru cooling - my boat has been like this for 10 yrs - kept my boat at harbortown on the barge canal for a couple years and polished the props plenty trying to get closer to ski island.....just make sure you dont let anyone flush the boat thru the drives (just put a hose in the strainer)
Thanks man I'm at Harbortown as well...shallow water even in all the channels! Definitely shallow around Ski Island and the island in Indian River. Also channels around 520 bridge are shallow. Great info
 
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I went with thru hulls as well. Same issue - Bravo-itis. Also installed drive showers. My marina put T,s in my intake line so that some water would still come thru drives. Much better cooling and now going thru the strainer catching all the junk that normally would go right thru the pump and clog up the heat ex changers. Had it this way for 2 seasons - very satisfied. Moor on a creek with water a shallow as 3.5 to 4 feet. Drives up and slow speed, no mud etc in strainer.
 
I went with thru hulls as well. Same issue - Bravo-itis. Also installed drive showers. My marina put T,s in my intake line so that some water would still come thru drives. Much better cooling and now going thru the strainer catching all the junk that normally would go right thru the pump and clog up the heat ex changers. Had it this way for 2 seasons - very satisfied. Moor on a creek with water a shallow as 3.5 to 4 feet. Drives up and slow speed, no mud etc in strainer.
Did they put in valves on either side of intakes ( drives or thru hulls ) so you can regulate the water flow as the water is going to flow from the easiest point. So if the drives are restricted the water will flow through the 1 1/4 thru hull and not though the drives. Is there any burning or overheating of the drive oil. There is a lot on the web about this.
One of my friends did this with shower drives and 1 year later his cone clutches went, Not sure if it is related to overheating the oil .
I would love to due this as there is not enough water flow from the 5/8 hose in the drive. I don't get how the go from 5/8 hose in the drive to 1 1/4 hose to the pump in the boat.
 
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I believe it was mentioned above, but you are MORE likely to suck up sand through the drive than via a thru-hull. Just think about it... the drive's pickup is lower than a thru-hull. And there is zero filtration for sand and small debris coming through the drive.

Yes, install the thru-hull. It's a better solution all around and even has extra advantages when it comes to flushing the engine. Just call your guy and say "do it".
 
I cut the hose at the drive and capped the end that goes to the motor. My drives ran noticeably cooler after this mod.
 
I do not have valves in mine. I do plan to put the upgraded hard plastic pipe in the drives if I have them torn down to that point. The hose going thru the drive has very little cooling effect on the drive. It is a closed system from the intake holes to the transom connection. I believe 95% of my raw water comes thru the thru hull. I also have drive showers, had them on a previous Br 3 and they cool the drive well. For 2 seasons now, my drive fluid is still blueish in color when it was changed. Doesn't look burnt at all. Also, engine temps at constant 165 degrees no matter what rpms and able to collect the trash and junk @ the strainer rather than at the heat ex-changer inlet.
 
Thanks man I'm at Harbortown as well...shallow water even in all the channels! Definitely shallow around Ski Island and the island in Indian River. Also channels around 520 bridge are shallow. Great info
Now Now - it's not that bad. I seem to do OK with my boat that I also keep at Harbor Town and it spends time at what's left of Ski Island as well as Bird Island and most of the others....
 
I do not have valves in mine. I do plan to put the upgraded hard plastic pipe in the drives if I have them torn down to that point. The hose going thru the drive has very little cooling effect on the drive. It is a closed system from the intake holes to the transom connection. I believe 95% of my raw water comes thru the thru hull. I also have drive showers, had them on a previous Br 3 and they cool the drive well. For 2 seasons now, my drive fluid is still blueish in color when it was changed. Doesn't look burnt at all. Also, engine temps at constant 165 degrees no matter what rpms and able to collect the trash and junk @ the strainer rather than at the heat ex-changer inlet.
Did you notice any difference in speed as they say the thru hulls will reduce the speed 3 to 5 MPH depending on which ones you have.
 
My 270 AJ 350 Mag Horizon and BIII came from the factory with a thru hull raw water intake and a grocco strainer. It doesn’t and never did take any water through the outdrive. My mechanic loves the setup and wishes all boats were so equipped. I’d say go for the change.

By the way, my father in-law has a 98 270 DA. His transom assembly is leaking and is being replaced.
 

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