Seawater Pump Access

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hi-ten

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I have a 2002 Wellcraft 3700 Martinique with the 8.1 HO 420 HP Mercruiser engines. I suspect I have a faulty starboard seawater pump and am having a bit of an issue understanding the procedure for gaining access to change the impeller. Anyone ever done one of these? Do you have any tips or suggestions as to the procedure? Thanks ahead of time for your thoughts.
 
Typically you need to turn off the seacock, open the cover and and pull impeller. An impeller removing tool helps.

That said I ve seen mercs with plastic pumps which needs to be removed to replace the impeller in which case the belt and hoses have go come off
 
Ok, so these engines are no fun...you simply can't just open the cover.

You have to take the ENTIRE pump off...which means remove the belt, loosen the 4-5 bolts, remove both the upper and lower hoses (these will be a pain in the butt).

If you are in the water, make sure your seacocks are closed of course...

Once you have the pump out...then you finish unbolting, take apart and do everything in reverse. I've done this a bunch, and the fastest I've gone is about 2 hours from start to finish. However I have very little room and have to basicallys stand on my head. You might have a bit more room, still a bit of work. Dang Merc just did not make this easy for us.
 
What too fast said. My best time was about 40 seconds. That's how long it took me to write the check after getting stuck in the bilge trying to DIY. You may want to bite the bullet and opt for a crank mounted pump. MAYBE 30 minutes per engine start to finish.
 
Thanks guys, I am a technician in the auto industry by trade so I have no problem digging in a getting it done, my inquiry was truly that of procedure. I will remove the belt and subsequent tensioning brackets etc. then hopefully I will be able to see what I am going after. Right now it is buried deep in the bilge and even standing on my head and using mirrors will make this challenging. I was hoping for that one tip to make things quick, clean and simple. Doesn't sound like its out there though. Thanks again for the tips.
 
The only tip to make it painless is not to buy a boat which doesn't have a standard raw water pump!

I made that mistake years ago with 7.4s. During the first service the dealer mechanic broke the pump housing... Some genius at mercruiser figured they could save $5 per engine with plastic vs bronze pump
 
If you don't have the manual for your engines...the manual has a pretty detailed how to...however if you are a tech, you will have no trouble, other than the dang access.

Also, this is to KiDa - there is a crank mounted option available ? If so, where do I find info on this, did a quick google and got lost pretty quickly.

thanks in advance!
 
toofast. It's not an option so much as a a correction to a poor design.

Les has them. Go to boatfix's new advanced search. Choose the manufacturer from the drop down list. I know Jabsco (BF has it listed as ITT Jabsco), Johnson and Sherwood make them.

Type "pump" (no quotes) in the keyword. That should narrow it down to about 15-20 pages per manufacturer. The pump you need depends on the engine and flow rate required. You will have to make or have made a bracket to hold it in place against torque. Not a biggie.

I've sent you an e-mail.
 
ouch, went thru three of the pictures and stopped when the exhaust was being dismatled. That's some great design Mercruiser.
 
quote:
Originally posted by PascalG

The only tip to make it painless is not to buy a boat which doesn't have a standard raw water pump!

I made that mistake years ago with 7.4s. During the first service the dealer mechanic broke the pump housing... Some genius at mercruiser figured they could save $5 per engine with plastic vs bronze pump

Click to expand...


It's been over a dozen years since I worked at a Mercruiser distributor, but I'm pretty sure I remember a very popular kit available from Merc to refit those horrendous plastic housings with metal. Too long ago for me to remember much more, but it was definitely available. P/N would have been 27-something or 47-something. One of those prefixes was gaskets and one was pumps, but - over a dozen years ago, so...

I DO remember that it was a 'by feel' job, rather than a 'see what you're doing' job.
 
I have a similar setup on my single Merc 7.4L. I can have the seawater pump off in less than 20 minutes unless the rear hoses give me a problem. What makes mine easy is the fact it's a single engine and I can sit down while doing it. I can understand the frustration with dual engines being tight together and stringers in the way.
 
The guy who engineered those RW pump setups for an annual maintenance item must be hiding in the witless protection program . Thinking in terms of all too common tight engine compartments, those pics are horrifically amazing.
 
Ply17410 ...Bob, Thanks for the link to the tutorial. Turns out my raw water pumps are fine. Somehow the closed cooling system froze and has fractured the block or heads and the coolant is leaking into the crankcase. I don't know what happened just yet, but this is gonna hurt.
 
hi-ten,

Sorry to hear about such mis-fortune. I noted in your original post your boat is 2002. The Merc 8.1s HO's ship with the extended life coolant which is good for 5 years. Last year mine (same engines as you) was at 5 years age and measured protection only to -25 which really had me nervous this past winter. Fortunately we store inside so I can tolerate some low temp swings. Fresh coolant is supposed to protect to -35. This was the first year with a boat with closed cooling and I didn't check the coolant strength until I was done winterizing! Definitely will move that UP on the checklist order next year.

If you have coolant available to check, check the freeze protection with a good hydrometer, not the test strips. Might give you an idea of what went wrong.

I called the tech support line of several extended life coolant manufactures and they all said that it will not freeze solid at the measured protection temp but turn to a slurry. it would take another 10 degrees or so for it to solidify.

I made it through the winter (on pins and needles) and am changing the coolant today. We splash next weekend.

Bob
 
NC, you cannot convert the plastic housing to a metal if they have a serpatine belt, which this one does.

The fastest way is to keep an extra overhauled pump on hand. I keep one on the shelf all the time, and I just remove the old pump with bracket intact, swap the bracket and bolt it back on. Can do it in 30 minutes.

When you overhaul the old pump, pay very, very close attention to the torque values on the through bolts, otherwise you may end up with an uncontrollable water leak (because the housing cracks easily) unless you have a sea cock intake, which many do not.
 
Ply17410...Bob, Thanks for the information. It turns out that the heat exchanger had a "latent defect" (tiny flaw) that allowed the sea water to mix with the closed cooling system and dilute that coolant to a less than suitable freezing point. Yes, it is now something that I will check at least twice a year with hydrometer. It is looking promising that because of its "latent defect" moniker that the insurance company may be liable for this repair. Keeping my fingers crossed for the surveyors report this afternoon. Thanks again.
 
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