Mahe 36: Volvo Penta diesel won’t rev up

[Rufduck]

A bit frustrated this year with my Volvo Penta diesels. D1-30B
Port engine at WOT is down to 2100 rpm from 3200 in gear and under way and now the starboard engine is only turning 2500 under same conditions. Both engines exceed 3200 revs no load.
Both engines seem to run fine up to the revs indicated as you advance the throttles. Beyond that point more throttle does nothing.
Observations...
Neither engine smokes at WOT. BUT port engine burps out soot on cold startup.
The throttle appears to move the throttle arm on the injection pump to full throw.
Each engine draws from the same common tank but have totally independent fuel plumbing, filters etc.
Saildrive oil is clean and unburned. Neither runs hot.
Both primary and secondary filters replaced or cleaned.
Same props for about 2500 hrs. Three blade folding.
Visual inspections of props for function or damage show nothing amiss.
No excessive vibration on either engine.
I even plumbed one engine direct to a separate fuel tank as a test for possible fuel blockage and tested last night. No change. The experience was educational and nearly embarrassing, however.
I Just removed the port air cleaner but was told that the engines would smoke if air limited. Also, they are more silencers than filters. No change in performance.

Getting pretty low on options.
Exhaust elbow where water is injected into the exhaust to cool it?
One or more Injectors partially blocked or not passing enough fuel? OR nozzles not atomizing fuel properly?

This sound familiar to anyone? Any thoughts really appreciated.

[ME Salty]

I am curious to see what responses you get. I have a cat with Volvo D2-55A engines. I have never had an issue with the port engine but the starboard has been troublesome. Last season I had fuel tank issues and had to have the tank pumped/flushed/cleaned due to a constant battle with algae which was thick enough to plug the intake tube in the tank. I also had old feathering props that had not been cared for (zincs) and were badly corroded and the pitch had been played with by the previous owner. They came on the boat. So this year I bit the bullet and bought 2 new Max props. So I know they are properly pitched and the season started of with both engines reaching 3100 rpm. Suddenly the starboard engine is just as you described. It has dropped from 3100 to 2400 and the other day it wouldn't quite reach 2000. I have checked everything you mentioned and I am guessing injectors. Hopefully someone will give some good troubleshooting tips.
Sorry I don't have the answer your looking for.

[Wotname]

Do a couple more easy things before worrying about injectors.

Pull and clean the exhaust mixing point and confirm exhaust system is not partly blocked.
Check / adjust valve tappet / rocker clearances.

[Rufduck]

Hmm? Where did my post from yesterday go? Try again...
Friday I pulled the port exhaust elbow. D1-30B. Coked almost closed. No overheating issues but I normally loaf along at 2000rpm and combined burn about 0.8-0.9 gal/hr (3.6/3.7 l/hr).
Anyway, after I had cleaned the exhaust passage, there was one chunk left near the exit of the casting. Removed it along with a chunk of the casting. Pretty easy to repair but...
Discovered HDI Marine in Vancouver, WA. (Almost neighbors). They stock more stainless exhaust elbows than I knew existed and the young lady there has goats that happened to be giving birth, if you need a cast SS exhaust mixing elbow, ask her how the goats are doing. I digress.
They have by far the best price and immediate shipping normally. PayPal so it’s easy. Sending me one with sales tax and fedx shipping about $270.
So, today I pulled the starboard one. Coking not as bad but nearly so. On the last test run, it would only turn 2500 max. Cleaned it up...almost perfect, just one more little chu...shucks! Ordered a second one from HDI.
On both of these, I could have stopped way before I did and both would have been serviceable for awhile. However, the iron was very brittle. Like chipping away on a coke bottle. I took a pick and tried cleaning some of the gunge from the inside of the water inlet port and a section of wall just chipped off.
There are 2 part numbers for the replacement SS casting...V878 and V834 (same price). The only difference is the OD (not ID) of the water inlet nipple. VP only lists one part number for the original casting and both the SS replacements reference the same number. Don’t know which one I need but have ordered the smaller and give it a go. After all, it couldn’t be worse than the John Deere voltage regulator that was installed in my airplane when we were stuck in the middle of nowhere but that’s another story.
Will post the results when all the dust settles.
Martyn

[Wotname]

Ahh... the adventures of the boat owner! Sounds like you are well on the way of resolving the RPM issues

[cuffy]

Good find and information. Thanks

[Rufduck]

Two SS cast exhaust elbows arrived this AM from HDI Marine in Vancouver, WA. They stock a bucket load of stainless exhaust elbows for different engine applications. Good prices as well.
Mine also came with new exhaust gaskets so my spare set are still spares. Wherever they ended up.
One puzzle is answered. There are two models available, V834 and V878. The only difference i found is only the outside diameter of the raw water inlet nipple. 3/4 vs 7/8 inch. With a bit of imagination either will work. The 7/8” V878 is temporarily out of stock for a couple of weeks but the young lady at HDI said I could exchange it if it didn’t work, so I gambled. I reused the small 90 degree feed hose and carefully cleaned the outlet and refaced the inside with a generous smear of hitemp silicone and let it cure. It slipped on easily and the hose clamp snugged it up fine. I believe that either one would work for the D1-30 series. They are the same price.
Installation was easier than removal and I was able to reuse the wet exhaust hose. I removed it with a slender flat screwdriver. Worked it on a diagonal and levered gently all the way around. Once free a bit of brute force rotated the elbow and I gradually worked it off. Once installed, I even remembered to turn on the raw water through hull.
Fired up both engines and no visible leaks, so we cast off and tooled out. The first impression was smoother operation. Second was a pleasant burble sound from the exhaust. Once out of the inlet channel to the house, I advanced both throttles...port engine 3200 starboard engine 2900. Operation was total success. The 300 rpm loss is probably a fouled injector as I had them opened up a dozen times to cure a small fuel leak.
Ran both for ten minutes at 2800 then 2500. No visible steam from either engine.
Takeaway...on a boat you know ran fine previously, if you experience low power, the first thought is fuel, ie filters. Next, maybe the prop is damaged but if you are considering hauling the boat out to check, pull the exhaust elbow before you haul.
It is easy to do. I used the following tools and stuff: 12mm combination wrench (sockets won’t fit the elbow studs), 7, 8 and 10mm socket wrench for clamps and air filter, slender flat blade screwdriver with a 1/8”-3/16” diameter shank. If you want to try to salvage the old elbows, find an old 1”-1 1/8” wood drill bit and an electric drill (they would have worked fine if I had just stopped there but I had to try for perfection), tube of hi temperature silicone.
Hope that this helps someone else.
Any questions, ask away.
Cheers, Martyn

[Wotname]

Thanks for the update and detailed report, glad you got it resolved.

[MKB53]

I have been browsing the forum catching up and saw all these posts. Pity I did not see them earlier. I could have saved you some time as I had been through the whole "won't rev" scenario followed by the "engine cuts out" scenario on my Mahe.

I am told that caustic soda will clean the carbon out but I have not tried.

I am about to replace the partially clogged elbows on my Lucia and fortunately stumbled on HDI marine, ordering a set last month. I am glad to hear Rufducks experience with them has been good. The price was damn near half that of a Volvo genuine replacement (in Europe) and stainless into the bargain.

I am told that the way to stop the buildup is to run the engines at full power for 10 minutes every couple of weeks.

[Rufduck]

Update…11-07-21
I mentioned a 300 rpm power loss on one engine (D1-30B) even after replacing the exhaust elbows (2019) and assumed it was due to a faulty injector.
After cleaning all three on the affected engine, it dropped to 200 rpm (wot 3000 vs 3200).
So, the last refuel I added 2 cans (40oz) of injector cleaner/fuel stabilizer (Royal Purple MaxTane) to the nearly empty tank and refilled with about 40 gallons to get it well mixed. Ran it for a couple of hours and let sit for a month. Yesterday, both engines ran 3200+.
Cheers, Rufduck

[team karst]

RE: V834 and V878

I tried to put on the SS replacement on my MD2030, and the OUTPUT hose needed to be 1/8" larger. I suppose I need to call them directly.

[Wotname]

Originally Posted by Rufduck

Update…11-07-21
I mentioned a 300 rpm power loss on one engine (D1-30B) even after replacing the exhaust elbows (2019) and assumed it was due to a faulty injector.
After cleaning all three on the affected engine, it dropped to 200 rpm (wot 3000 vs 3200).
So, the last refuel I added 2 cans (40oz) of injector cleaner/fuel stabilizer (Royal Purple MaxTane) to the nearly empty tank and refilled with about 40 gallons to get it well mixed. Ran it for a couple of hours and let sit for a month. Yesterday, both engines ran 3200+.
Cheers, Rufduck

Another great outcome, thanks for letting us know.