through-hull fitting and a sea strainer

[cmk245]

Debating installing Flanged thru-hull fitting (with valve)and sea strainer for Raw Water pump (belt driven). and re-routing outdrive pump output thru transom as other members have done. My question is should I get the 1-1/4" size thru-hull or would 3/4" size work OK? The inlet and outlet on pump are 1-1/4" but as the OEM drive's outlet hose thru transom is only 3/4" also but connects to 1-1/4: hose at end of plastic outlet pipe.

Any ideas on this?

 

[Fun Times]

Re: through-hull fitting and a sea strainer

Hi there, It is recommended by the engine manufacturers to only use 1-1/4" seawater pickup thru-hull and hose.

 

[cmk245]

Re: through-hull fitting and a sea strainer

Yeah, I was trying to find that recommendation but could not. Have been looking for other posts with pictures of setup and how valve and strainer is ran and hose routing.

Thanks for your reply.

 

[thumpar]

Re: through-hull fitting and a sea strainer

Do you have the belt driven seawater pump already or are you trying to convert the whole thing over? What is the reason for the change?

 

[Fun Times]

Re: through-hull fitting and a sea strainer

Have been looking for other posts with pictures of setup and how valve and strainer is ran and hose routing.

This archived thread comes to mind as being helpful with pictures, http://forums.iboats.com/mercruiser...tdrives/bravo-iii-overheat-issues-597927.html

 

[cmk245]

Re: through-hull fitting and a sea strainer

Do you have the belt driven seawater pump already or are you trying to convert the whole thing over? What is the reason for the change?

Let me start with this.
I have a 5.7 closed cooling engine with "Factory" San Juan LARGE heat exchanger. The engine was using raw water thru stern drive. I have recently purchased 5.7 inboard engine that had rebuilt belt driven raw water pump on it. I purchased the inboard for parts and used remote oil filter setup, fuel filter and lines,etc. I sold most of the inboard only parts.

I'm questing if I should use the belt driven pump with NEW thru hull seacock setup and run existing drive output back overboard. NOW would be the time to do the thru hull thing before I finish bilge painting and installing engine. Many have told me including san juan that stock alpha water pump would handle cooling OK. But many others have said to use the belt driven pump as it is better and easier to work on if needed. and I have it.

So,Yeah I was thinking of converting it over and needed input on if it's worth the work and $$$ of new flanged thru hull and strainer.

Thanks Guys , sorry for the rant but wanted all to know what I. asking...

 

[thumpar]

Re: through-hull fitting and a sea strainer

What was the original drive and setup?

 

[cmk245]

Re: through-hull fitting and a sea strainer

Original drive was/is alpha gen 1. the motor is new to the boat (1982 260 searay) original was seized. and was raw water cooled. closed cooling motor came from another boat with stern drive cooling, and believe that setup worked OK.

 

[Fun Times]

Re: through-hull fitting and a sea strainer

I'm questing if I should use the belt driven pump with NEW thru hull seacock setup and run existing drive output back overboard. NOW would be the time to do the thru hull thing before I finish bilge painting and installing engine. Many have told me including san juan that stock alpha water pump would handle cooling OK. But many others have said to use the belt driven pump as it is better and easier to work on if needed. and I have it.

From all the past reading I have seen on this subject there are lots of mixed suggestions of what works well and what don't including the known average water temperature of the body of water the boat is usually ran in while using a particular stern drive model vs another stern drive model.

Since it seems like you plan to run both a sea strainer and a closed cooling system then for your best overall results, you would be much better off installing the thru-hull fitting in order to guarantee you are getting adequate water supply vs trusting the small vane sea water pump impeller found in the older alpha stern drives that is questionable for what your trying to accomplish.

Also bear in mind that there is a chance that if you use the alpha impeller along with the new inboard engine thermostat housing, you may experience an overheated condition due to on some engine models, the thermostat housing is designed differently to work with a particular engine model that can be affected by impeller design/water flow rate. There is also closed cooling thermostat housings that could be affected by inadequate water flow both in and out but mainly it's water flow out.

Just be aware that there are different thermostat housings for the Alpha/Bravo/inboard/closed cooling/non closed cooling, and the list could go on and on with different engine models/manufacturers.

I believe you may have been looking for page 16 earlier,
http://www.boatfix.com/merc/Install/gas/86017211.pdf

Do you trailer this boat or leave it in a slip most of the time? If in a slip, be sure to set it up for easy fresh water flush.

 

[cmk245]

Re: through-hull fitting and a sea strainer

Thanks for everybodys input. Looks like I ought to go with using belt driven pump with thru hull/shut-off valve . Is the strainer that important? as I see systems without and if I do a tee after valve I could add fresh water flush port there. Are strainers standard equipment on inboards and bravos using belt driven pump? I have seen systems with and without strainers. Space and cost would be considerations.

The only cooling system part from the inboard motor will be the raw water pump.The closed cooling system I have is Merc. system with t-stat housing with 2 ports going to bottom of center rise manifolds Risers and blocks between manifold and risers have hoses returning to heat exchanger. It is a FULL system.

I see in the boatfix link that owner installed thru hull pickup while boat is on trailer (missing rollers),(Mine is on blocks) and I am worried about placement if I get a trailer and rollers may hit pickup.I guess there is NO standard placement other then where I can fit it.

I will be boating in salt/brackish water and most likely in slip as too big to tow around for me. 5500 lb. boat with 8ft. beam trailerable ,but would be a bear . and as of now I have no trailer or truck big enough to tow.

I appreciate all the help with this.

 

[Fun Times]

Re: through-hull fitting and a sea strainer

Are strainers standard equipment on inboards and bravos using belt driven pump? I have seen systems with and without strainers. Space and cost would be considerations.

Strainers are not standard, but just a nice accessory item to have installed if cost is not a factor. Some areas are more in need of them than others.

Good luck.

 

[thumpar]

Re: through-hull fitting and a sea strainer

I don't have a strainer on my Bravo. We boat in freshwater but the lake has lots of weeds. There have been times late in the season when the water is warm and the weeds are growing like crazy we have had to stop to clean the outdrive off but the cooling is fine.

 

[stratcat88]

Re: through-hull fitting and a sea strainer

Debating installing Flanged thru-hull fitting (with valve)and sea strainer for Raw Water pump (belt driven). and re-routing outdrive pump output thru transom as other members have done. My question is should I get the 1-1/4" size thru-hull or would 3/4" size work OK? The inlet and outlet on pump are 1-1/4" but as the OEM drive's outlet hose thru transom is only 3/4" also but connects to 1-1/4: hose at end of plastic outlet pipe.

Any ideas on this?

hey cmk. i also have a 5.7 with a closed water system. the mech. that worked on my boat closed off my stern drive supply commin through the transom, but didnt take out the impeller or have a way for the water to dump out.and my drive leaks fluid out of the water intake so i,m putting in new seals. my new water pick up never hits the trailer so thats cool.it has inch and a quarter hose with no valve which is scary,but it has a strainer before the power steering cooler.its good to see the water flow.but i got to tell ya, just running the closed system, those manifolds were nice and a little over ambient temp. get the strainer.

 

[Scott Danforth]

Re: through-hull fitting and a sea strainer

Let me start with this.
I have a 5.7 closed cooling engine with "Factory" San Juan LARGE heat exchanger.

Mercruiser never used San Juan. They did use Monitor and CHAMP (now Alfa Laval). They never did use San Juan.

San Juan makes aftermarket kits only.

 

[Scott Danforth]

Re: through-hull fitting and a sea strainer

Regarding strainers, my experience is the first heat exchanger in the system makes an effective strainer. this is usually the power steering cooler.

A good strainer will have a large diameter basket that can be cleaned from inside the bilge and will not impede raw water flow