D1-30 cannot get above 2000rpm and its not the prop or fuel

Neeves said:
You mention that you have a stainless elbow and appear to dismiss the idea that it might be blocked.

Has it been checked.

Checking would take maybe 15 minutes.

I am aware that a few members here have swapped from a cast to a stainless elbow. I can fully accept that a well made stainless elbow will reduce the problems of corrosion in the Volvo cast elbows. However it has never been clear if a stainless elbow is not subject to the calcium build up and blockage of the cast elbows. To put it another way - the calcium build up is a function of the elbow being cast - or its going to occur in any elbow.

I have never seen anyone comment on calcium build up, or not, on stainless elbows - but have not made a specific search.

Jonathan
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Thanks for that. The mechanic said he checked it and was comfortable that wasn't the problem but I think I'll take another look myself next time I'm out on the boat just in case. It's strange though to suddenly go from 3200 down to 2000rpm almost instantly. I would have though a build up world have been a gradual loss of power, not an instant one
 
Gavdog said:
Hull has been cleaned and the other sides engine gets to 3200rpm so it's definitely not the Hull. Thanks tho
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no idea what a D1-30 is, but turns out it's a twin engined boat, would be helpful if you gave some more info on the first post tbh.
so, is it on outdrives, is it a cat on saildrives (but then you'd say hulls not hull!), or a mobo?
if outdrives, then the rubber bush in the prop of the engine that goes up to 3400rpm could be to blame and actually the engine you're trying to sort is the one that is doing all the work and is fine.
I guess easiest thing to do is go out on the 3400rpm engine alone, the other in neutral and see if the boat actually does much, then turn that engine to neutral and run the 2000rpm one and see if it goes any faster...
but I'd guess your mechanics would have picked that up already...
 
S drives can have a variety of props and as most are fitted to sail boats which then gives a choice of 2or 3 blades fixed folding feathering etc some similar to out drive
So most will have some form of bush but not all and for those that do its not such problem as on high speed boats
but blades falling off or sticking is not unknown
 
Perhaps the problem is on the other engine. The revving engine isn’t actually doing much work leaving the ‘problem’ engine under-revving and struggling.

Just read Vas #25 ?

Edited: if you’ve got folding props maybe the one on the ‘good’ engine isn’t opening fully.
 
I would have a look at the wet exhuast hose, at high hours the inside of the hose can peel away causing a blockage which then increases back pressure preventing you achieving much in the way of revs. Pipe still usually looks fine on the outside!

Usually it happens close ish to the engine in the drop to the water lock.
 
Gavdog said:
Hi everyone. This is my first time posting on a forum as I'm desperate and have not been able to find a solution despite multiple boat mechanics and reading loads of forums. My d1-30 is now refusing to go above 2000rpm (sometimes it goes to 2400rpm but then drops back to 2000rpm slowly and then will not go back up). We have replaced the throttle cables, cleaned the folding prop, checked for any prop obstruction but no luck. Injectors have been swapped, fuel lines checked and filters changed, I've even attached tote tank direct bypassing the lift pump and nothing ever changed the rpms at all. Always the same. It should rev around 3200-3400rpm. When I get to 2000rpm the throttle still has room to move but it doesn't increase the revs any further. The mechanics have now given up so I'm open to any suggestions and advice. Thank you!
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Colour of exhaust should be clue at certain revs.if white smoke(steam) is obvious without realization. I had my exhaust elbow replaced mistakenly because of restriction at the rubber right-angle water inlet at top of elbow. (The exhaust elbow itself was clear (1600 hrs) so now have spare for sale) . Mine is also a D1 30.
 
Are you sure it's actually revving low. A similar thread some time back revealed that the tacho was at fault and the engine was actually working fine.
 
Oh gees, I'm hopeless. There I was thinking that no one was replying and turns out I wasn't seeing the notifications for some reason. I'm so sorry everyone!

Anyways, I'll answer your questions below each of your quotes as the puzzle remains. I have now removed the exhaust elbows of both engines (both are stainless) and they seem to be fine. I'll do a cleanup just in case but they certainly don't seem to be clogged in anyway. I'll replaced the thermostats as precautionary while I'm at it. Unfortunately one of the coolant nipples/bleeding cocks was broken by the looks by the previous owner and cannot be removed so I need to work out a way to drain the rest of the coolant before I can remove the heat exchanger tubes. That will only help deal with the overheating though, not the loss of revs. Answers below, still very keen on thoughts now that I know there was still interest as I'm still stuck as are the boat mechanics (tried 2 more)

scottie said:
Are you getting black smoke in either engine and how does the max boat speed using one engine at a time compare?
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White smoke + Black substance on starboard engine (think may be steam + soot?) but that's the one that revs still to 3400rpm. Dealing with coolant issues as per above to sort steam issue hopefully but less sure on black substance. Elbow is black but hard and not clogged.
Port engine (which is the problem one that only revs to 2000rpm) does not smoke at all, just doesn't power up except in neutral.
Thanks so much and apologies again for not seeing your post!

Iliade said:
Inlet manifold or air cleaner gunked up? Does it issue black smoke?

Can it achieve high revs in neutral? If not, possible governor issues.

Try cracking each injector in turn. If one doesn't induce a drop in revs you have a problem.
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New air filter, no difference at all. Manifold doesn't seem to be clogged at all but is hard black around inner lining.

Yes, high revs fine in neutral and reverse.

Injectors seemed fine according to mechanic when he cracked them and they had just been swapped with starboard engine in case and no change.
Thanks so much and apologies again for not seeing your post!

jwfrary said:
I would have a look at the wet exhuast hose, at high hours the inside of the hose can peel away causing a blockage which then increases back pressure preventing you achieving much in the way of revs. Pipe still usually looks fine on the outside!

Usually it happens close ish to the engine in the drop to the water lock.
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You mean the big massive black one leading out of boat? If so that hose seems to be fine.
Thanks so much and apologies again for not seeing your post!

jackho said:
Colour of exhaust should be clue at certain revs.if white smoke(steam) is obvious without realization. I had my exhaust elbow replaced mistakenly because of restriction at the rubber right-angle water inlet at top of elbow. (The exhaust elbow itself was clear (1600 hrs) so now have spare for sale) . Mine is also a D1 30.
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As per above, no smoke on port side at all. Right-angle water inlet is running clear.
Thanks so much and apologies again for not seeing your post!

sogood said:
Are you sure it's actually revving low. A similar thread some time back revealed that the tacho was at fault and the engine was actually working fine.
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Yep definitively lower revs and no power gain part 2/3 in throttle in gear.
Thanks so much and apologies again for not seeing your post!

Iliade said:
Where is the boat Gavdog?
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Hobsonville, Auckland, New Zealand :)
Thanks so much and apologies again for not seeing your post!

Thanks everyone!
 
I had the very same thing happen on my D2-40, and equally some of our school boats. Turns out on all occasions it was the clutch pack in the Saildrive that had gone.

It took ages to work out. Even the local Volvo Penta engineer had no clue what it was. It was odd in that the engine would fully rev-up in neutral, but in-gear it wouldn't go over 2300rpm. Swapped over the saildrive for a new one and bingo, solved. Then stripped-out the old clutch pack which was rebuilt (beware - clutch kit pack from Volvo is ruinously expensive), and thats now fine as well (used it in one of our school boats).
 
I don't know, obviously, the design of your exhaust elbows but you mention that the deposit is hard, common. But if the deposit actually reduces the ability of the engine to feed the water through the elbow then the engine will run slow.

You say the other engine is fine. Then take the elbow off the good engine and replace onto the engine that is questionable (this sort of trick is an advantage of having 2 engines). This will eliminate the elbow as the guilty party. You could take the injectors off the good engine and swap them as well - but I'd work one variable at a time. Air intake is another variable easy to swap

I don't know if you have mentioned it - on what boat is the installation?

I assume you have done compression on each cylinder.

Jonathan
 
Beware that the hose can look new on the outside but peel away on the inside causing a blockage. Back pressure would cause the effects your seeing.

As your getting different readings out of gear on the two tachometers then I would be tempted to do a full power on one engine then full on the other engine and see what speed your achieving, this would give you a rough guide as to if your looking at an actual engine issue or just a tacho issue.
 
You describe earlier how the fuel lever travels to the point at which the engine reaches its maximum speed and though the lever continues to move to the full range high speed stop without speeding up any more. If there is no sigh of the engine trying to speed up then it suggests there is a governor problem . Does the engine respond in exactly the same way if you run on the faulty engine and leave the good engine in neutral If it does behave the same and no sign of overload then the governor needs to be inspected including the linkage to the fuel pump.
 
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