Volvo D6-435 Impeller Change (C-30S)

JDubya

Active member
Joined
Sep 30, 2022
Messages
29
Fluid Motion Model
R-23 (Sterndrive)
Hull Identification Number
FML30C07J021
Vessel Name
Couples Therapy
MMSI Number
368277690
I've been researching my first attempt at a raw water impeller inspection and change out. It seems like I should just put in a new one if I go so far as to get that close to it. I've owned the boat for about 18 months and it's at 188 hours (bought it used, with ~70 hrs) so it seems like it's time, and I'd like to think I could do this on my own.

What I'm not 100% sure of, is whether I'll need to pull the serpentine drive belt off the sea water pump as part of the impeller replacement. The D6 Owner's Manual says yes (page 114, step 4) ... but a workshop manual that Pacific Power Group sent me is silent on the matter.

I don't have any experience with the belt, and at my current level of DIY maintenance skills removing and reinstalling it seems like a pretty daunting task given that you'd essentially have to do it all by feel on the C-30, with maybe a tad bit of help from an inspection mirror.

Any discussion and advice from someone that's changed out the impeller on this engine a few times would be greatly appreciated! YouTube has lots of videos, but I can't find anything that's specific to the D6-435 or that addresses the belt question.
 
I will give you my opinion. Loosen the tensioner and remove the belt. This will serve two purposes. (1) make it easier to to walk the old impeller out and walk the new impeller in by turning the pulley. You will be able to turn the pump pulley with the belt off.(2) When is the last time you checked and adjusted belt tension? The D4 and D6 belt tensioners are not spring loaded. The belt tension must be adjusted by hand. There are instructions with torque specs in your manual. Unfortunately the access is not favorable but it is doable. The best time to figure out the method of belt replacement is when you are at the dock not underway, making way. The reliability of serpentine belts is very good as long as it is adjusted properly. This is the reason most applications using serpentine belts have self adjusting tensioners. Volvo Penta did not use that application with the D4 and D6 engines and recommends inspection every 200 hr or ONCE A YEAR (12 months) which ever comes first. If you are a typical boater that is not cruising full time use the years (months) as a maintenance reverence not hours. Marine age (years) is more important than hours when maintaining a boat. The Volvo recommendation for the impeller is to inspect every 200 hr or every 12 months (inspect) If you are inspecting the impeller you are changing it! Many DIY boat owners and even Marine technicians look at hours for maintenance. I recommend marine age over engine hours unless you are a full time cruiser.

Volvo Penta will state inspect( I ) This leaves the judgment to the mechanic that is looking at the machinery. Volvo Penta will say Replace ( R ) this is not a Judgment call. The Replace is either hours or years. One item that many over look is the coolant. No hours / every two years. 20 hours, 1000 hours it does not matter. Reason is, there are many dissimilar metals used in the cooling system.

When it says inspect. That is a judgement call as to what you do. It does not say do not replace!

The belts have a 800 hour service life or 5 years. The average boat owner will not put 800 hours on the engine in 5 years. Full time cruisers will but not weekend warriors!

Example: I purchased a 2002 Mainship Pilot in 2021. The two Yanmar engines had 850 hours on them. 19 years in service 850 hours. Theses engines should have had the 1000 hour service, 2000 hour service already done at 19 years. Marine age supersedes hours. I did the 1000 hour when I purchased the boat. Last year I did the Loop and put just over 800 hours on the engines in 14 months. I did (4) 200 hour inspections and (1) 500 hour inspections to the engines in one year. Over the winter I did another 1000 hour inspection that included some of the 2000 hour recommendations.

Long story to say Change the impeller, remove the belt inspect and adjust to manufactures specifications. Don't over look all the recommendations. Inspect ( I ) means inspect and or replace. Replace ( R ) means NEEDS to be done!

( Tension the belt by applying a torque to the tensioning roller square fitting of 70 Nm (52 lbf.ft). Lock the tensioning roller using the mounting bolts. After the adjustment is made to spec confirm the bolts are tightened to 50 Nm (37 lbf.ft). )
 
Brian thank you for your technical support. We bought a C28 new in 2021 and your advice has helped me in doing things properly. Thanks again hope you have a great boating season.

Rob Miller Sechelt BC
 
Brian,

I'll second Rob's sentiment on your responses; I also find your postings in this forum very helpful, and appreciate your opinion on this as well.

It does make sense to me that the belt would need to come off for this in order to deal with the impeller -- if I understand the owner's manual correctly, it has you check that you can't rotate the pump by hand before removing the belt, to make sure the pump internals aren't slipping and need repair.

The belt was removed and reinstalled last December in the boat yard, when they had to pull off the fuel pump to make a fill repair underneath my forward port side engine mount. They would have put it back on and tensioned it afterwards … another good reason for me to check it myself now.

I'm fully aligned with sticking to the (I) vs (R) per the Volvo service schedule and am working to get on schedule with this year's spring maintenance. I probably should have done the impeller last spring since the boat was a year old when I got it. I'm probably more nervous about the belt work than I should be, so I just need to jump in and figure that out. As you say, this is a skill that I will desperately need if I ever have a belt issue while underway, and I get that I'm taking a risk every time I get underway without having it!

As a side note, the service schedule I have for the D6-435I-F, found by searching by my engine serial number on Volvo Penta's website, lists coolant as an (I) every year/200 hrs and an (R) every 4 years/2000 hrs. I wonder if that's an updated service interval with the newer yellow coolant.

___________________________________________________________________
So ... any advice out there from those with a D6-435/440 and as little room to get at the engine belt as there is on the C-30?

I'm just looking for any thoughts regarding getting prepped for my first attempt at removing and re-installing the belt. I've got the instructions in the owner's manual, but if anyone has any tips or tricks you learned the hard way then I'm all ears. I'd be especially interested what brand/size of torque wrench might work best in that space, especially since I'll have to do a lot of it by feel or with an inspection mirror.
 
Just to provide a counter point for this maintenance item, I do this myself and I just remove the front of the pump housing with the seawater hose in tact, and remove the impeller with two needle nose pliers. I use glycerin soap to put in the new one. I’ve done this 3 times now and have never had an issue.
 
dbsea":koe75hy8 said:
Just to provide a counter point for this maintenance item, I do this myself and I just remove the front of the pump housing with the seawater hose in tact, and remove the impeller with two needle nose pliers. I use glycerin soap to put in the new one. I’ve done this 3 times now and have never had an issue.

Yes this can be done and it is the way I do impeller changes on my Yanmar 4LHA STP because the pump is gear driven. The complete pump needs to be removed to turn the pump to walk it in. Your method is a good method if the impeller fails while underway making way. It is quick. I make suggestions of changing items and servicing items based on preventative maintenance. If I have an impeller that I am changing because I believe age and engine hours dictate a impeller change. I look at what other items are inline for servicing. This keeps all maintenance item on a schedule. In three impeller changes how many times has the belt been checked and adjusted for proper tension? The belts have a good reliability rating but need to be adjusted with proper tension to make 5 years or 800 hours. The belts will last much longer if maintained but why take a chance?

.
JDubya":koe75hy8 said:
As a side note, the service schedule I have for the D6-435I-F, found by searching by my engine serial number on Volvo Penta's website, lists coolant as an (I) every year/200 hrs and an (R) every 4 years/2000 hrs. I wonder if that's an updated service interval with the newer yellow coolant.

The yellow coolant has been used for a number of years. Volvo changed some of the metals used in the coolant system, Heat exchanger, after cooler. This may have extended the use of the coolant and is the reason the raw water side no longer requires anodes for protection and the coolant side has extended life of coolant. With antifreeze I don't look at hours. I actually think the antifreeze last longer if it is circulated frequently at a higher temperature. I'm more concerned about antifreeze in the engine that has stayed stagnant for long periods of time. 4 years and 200 hours of use is worse than 4 years and 2000 hours of use in my opinion. Again this is a judgement call to the DIY owner or the maintenance marine technician. I'm on the side of changing sooner than later. My opinion
 
100% agree Brian. I won’t change / tighten the belts on the boat because I simply can’t access it. It’s about the one item I have a mechanic do, on the recommended maintenance schedule.
 
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