Engine overheating when motorsailing upwind

[theglo]

Originally Posted by GreenWave

on the shaft issue... if you think it gets worse (i.e. drag on shaft) depending on conditions, lean etc then you might check your motor mounts. If one or more are bad then the shaft position can change with boat lean, rpms etc. Ask me how I know.


Aside from that I would be checking coolant levels, raw water intake for debris, and make sure my prop is clean.

THANKS. I will look at these as I adjusted the crap out of them when aligning the new transmission.

[wyb2]

Originally Posted by rslifkin

Not entirely true. Diesels are governed, so if you're requesting 2000 RPM, the governor on the injection pump will vary the amount of fuel injected to maintain 2000 RPM. So it'll work harder and burn more fuel in gear than it would in neutral at the same RPM. And if you make the boat harder to push (or the shaft harder to turn), the engine will see more load at a given RPM. If something is holding boat speed back, the engine likely won't reach rated RPM at full throttle as it won't have enough power to overcome the extra load.

This is what I was thinking.

Though to play devil’s advocate, on older engines, wasn’t the throttle basically tied into the mechanical fuel injection system? So X amount of throttle asked for X amount of fuel, and the rpm’s were just a byproduct of that?

Even then though, it seems like X amount of fuel could provide a range of different efficiencies, so different loads, at the same throttle position (though maybe different rpm’s). Where as a newer engine might provide different loads at the same throttle position AND rpm by varying the fuel behind the scenes.

[wyb2]

Originally Posted by theglo

Speed from gps. Would have pointed into seas as well. Boat speed would drop to under 1.5 knots without main sail up.

I could have dropped off the wind and sailed but was really looking for that night lee of Puerto Rico (which did arrive almost 25 miles offshore). Plus wife and kids were sleeping and sailing off wind introduces a LOT of heel on my boat.

Fair enough, 1.5 is pretty painfully slow.

My pet theory was the reverse shot changing something about a feathering/folding prop or cleaning off or otherwise somehow changing your paddle wheel reading. Guess I’m out.

[rslifkin]

Originally Posted by wyb2

This is what I was thinking.

Though to play devil’s advocate, on older engines, wasn’t the throttle basically tied into the mechanical fuel injection system? So X amount of throttle asked for X amount of fuel, and the rpm’s were just a byproduct of that?

On an automotive diesel that's often the case. Marine diesels are almost always governed like an industrial engine though, so the throttle just sets the governed speed target. That's why the RPM doesn't drop much when putting the engine in gear, for example, but the engine sounds like it's working harder.

[wyb2]

Originally Posted by rslifkin

On an automotive diesel that's often the case. Marine diesels are almost always governed like an industrial engine though, so the throttle just sets the governed speed target. That's why the RPM doesn't drop much when putting the engine in gear, for example, but the engine sounds like it's working harder.

That makes sense, thanks.

My vote is the engine temp gauge going from 5/8 to 1/2 is just the result of pounding at 2.5 knts vs cruising at 5 knts at a similar prop/engine rpm.

Wait, OP, you changed the transmission? Exact same final drive ratio as before?

[deblen]

You changed the transmission. Is gear ration of new transmission close to the old one?
Is/was either transmission water cooled?
Check the suction hose from seacock to RW filter & from filter to RW pump input for collapse under suction at higher RPMs.
Why is boat so slow?
HP/model of engine?
Cheers/Len

[theglo]

Originally Posted by wyb2

That makes sense, thanks.

My vote is the engine temp gauge going from 5/8 to 1/2 is just the result of pounding at 2.5 knts vs cruising at 5 knts at a similar prop/engine rpm.

Wait, OP, you changed the transmission? Exact same final drive ratio as before?

Not exactly the same ration. I went from a Hurth HBW100 (1.79 to 1 gear ratio) to a ZF15M 1.88:1 gear ratio.

I agree with the over-temp, but what about the change of speed from 2.5 knots to 4+ knots, even when going into the wind, if I bump it into reverse for a moment and back into drive. Usually lasts about 10 minutes before reverting to 2.5 knots AND (I didn't mention this before) I believe that change is accompanied by a sound of the engine maybe working a bit harder....

I say that with a lot of caveats, I.e. I'm not 100% sure it sounds different, except that I spend a lot of my time sailing listening to the boat and, the other 4 people on board swear there is no sound difference, but, I'm pretty sure I hear something change when it happens.

So, yeah.

[wingssail]

Originally Posted by theglo

Good morning! (Problem with hints below it). I appreciate any assistance!

PROBLEM: My engine is overheating a bit but ONLY when motorsailing upwind and heeled over.

BACK GROUND: I have a 41' monohull with a new ZF15M transmission replacing the previous Hurth transmission. I replaced it myself in Georgetown Bahamas a few months ago and have driven it to Puerto Rico. It's been a lot of motorsailing as its all upwind.

BACKGROUND #2: I crossed the Mona Passage 2 days ago and was motorsailing into about 20 knots of wind right in my face. The boat was well heeled over with a reefed main up and the engine running at normal RPMs. I was averaging 2.5 to 3 knots of forward progress. I was running at night so couldn't see anything but on a few occasions I threw the engine into neutral, then reverse, revved it up for a moment, and then back into forward, same RPMs, and suddenly I'm getting 3.5 to 4 knots of boat speed for, maybe 10 minutes, and then back down to the 2.5 to 3 knots after a while. The boat also was slightly overheated during this time. As in, 5/8 of the way to WAY overheated on my gauge, but not the usual 1/2. At first I thought it was Sargassum weed that I had caught... but?

Then, to make myself KNOW (or at least I'm pretty sure) there is an issue, at about 3 AM I hit the night lee of Puerto Rico and the wind stopped completely and the seas went flat. I was able to point directly at my destination, and rev the engine up an additional 300 RPM. Running flat and calm I was now traveling 4.5 to 5.5 knots and the engine temperature actually COOLED to normal operating temp.

MY GUESS: I aligned the engine to the new shaft coupling. I think I need to align the prop shaft first, to the shaft hole (log?) in the boat. I think that when I am motorsailing (only main up), and the boat is well heeled, the shaft may be hitting the shaft hole and causing quite a bit of resistance.

QUESTION: Anything else I need to look at that I may have effed up?

Thanks CF world!

I'd still vote for reduced water flow. When heeled over there is a large trough in the wave your boat produces and that trough often reaches nearly to the keel. The water may be foamy at the location of the intake and may periodically catch air.

But honestly, you have a fantastic sailing boat which is particularly good upwind in a breeze. You can make 3-4kts VMG tacking upwind with a small jib and reef the main if needed. I assume you have a small jib on board. Take off the big genoa and put on the small jib before you go out in windy weather. You will find the boat transforms into the sweetest upwind boat you have ever been on. (I don't mean that it is pleasant beating into 20kt winds, but neither is motoring with the main up). And I doubt if it will take longer than the "motorsailing" you are doing, but if so, so what? And you will save wear and tear on the engine and drive system. And this current problem will go away.

[theglo]

Originally Posted by wingssail

I'd still vote for reduced water flow. When heeled over there is a large trough in the wave your boat produces and that trough often reaches nearly to the keel. The water may be foamy at the location of the intake and may periodically catch air.

But honestly, you have a fantastic sailing boat which is particularly good upwind in a breeze. You can make 3-4kts VMG tacking upwind with a small jib and reef the main if needed. I assume you have a small jib on board. Take off the big genoa and put on the small jib before you go out in windy weather. You will find the boat transforms into the sweetest upwind boat you have ever been on. (I don't mean that it is pleasant beating into 20kt winds, but neither is motoring with the main up). And I doubt if it will take longer than the "motorsailing" you are doing, but if so, so what? And you will save wear and tear on the engine and drive system. And this current problem will go away.

Thanks. I know I am not a particularly good sailor... but, am learning. We swapped out the 125 Genoa in the DR and replaced it with a 100 JIB. Running that with a reefed main worked fantastic for the first 100 miles out of Puerto Plata on our most recent run towards Puerto Rico. My guess is it would work well as well for the sailing I was doing the other night. My only hold back was, I'm not a fantastic sailor, motorsailing was working, and we were doing all these passages in the middle of the night, with my wife and 3 kids on board. The motorsailing was working, albeit slowly, and I didn't want to mess with it as long as it was. BUT, from here on out down the Caribbean we have a bunch of short sails each day and, before I hit Grenada, I'm going to know how to sail this boat.

[Peregrine1983]

Originally Posted by deblen

You changed the transmission. Is gear ration of new transmission close to the old one?
Is/was either transmission water cooled?
Check the suction hose from seacock to RW filter & from filter to RW pump input for collapse under suction at higher RPMs.
Why is boat so slow?
HP/model of engine?
Cheers/Len

My thoughts too. The boat sounds a bit slow.

But also.... have you checked the coolant level? I'm wondering if the heel is sending the remaining coolant to one side and the impeller is running dry.

[ItDepends]

If you are pointing so close to the wind that the boat is going SLOWER than it does in calm conditions, you are not really motor sailing, you are motoring with the sail up. The sail is likely adding more drag than drive, forcing the engine to work harder, and if your cooling is marginal for some reason it gets hot.

If you are making 2.5 knots at cruising rpm, your engine is probably working really hard. If you took the sail down would you go faster? Or slower under those conditions?

[theglo]

Originally Posted by Peregrine1983

My thoughts too. The boat sounds a bit slow.

Have you checked the coolant level?

I have a very small coolant leak and therefore I check the coolant all the time and top it off as needed. I may have added a cup during the last 50 hrs of engine run time. I don't think it's coolant related.

[Peregrine1983]

Originally Posted by theglo

I have a very small coolant leak and therefore I check the coolant all the time and top it off as needed. I may have added a cup during the last 50 hrs of engine run time. I don't think it's coolant related.

Gotcha. Just a lesson from my experience though - I had a slow coolant leak for a long time, but then one day it was a big leak and I didn't know it until my engine was getting hot

I hope you figure it out!

[theglo]

Originally Posted by ItDepends

If you are pointing so close to the wind that the boat is going SLOWER than it does in calm conditions, you are not really motor sailing, you are motoring with the sail up. The sail is likely adding more drag than drive, forcing the engine to work harder, and if your cooling is marginal for some reason it gets hot.

If you are making 2.5 knots at cruising rpm, your engine is probably working really hard. If you took the sail down would you go faster? Or slower under those conditions?

I'm not sure if this answers your question, BUT, when I was motorsailing (wind in the sail) I was actually point about 10 degrees off course. The wind was coming directly from where I wanted to go. If I turned directly into the wind and the sail just blew around aimlessly I would lose boat speed from 2.5 to 3 knots down to 0.5 to 1.5 knots. That is under engine alone, with no wind help, and perhaps some wind resistance from the sail banging about.

If I fell off just 10 or 15 degrees more, maybe 25 degrees off the wind, I could maintain almost the same boat speed (3 knots-ish) with just a reefed main sail and the engine OFF. I did this for an hour while I checked things over because of the overheating.

Thanks

[theglo]

Originally Posted by Peregrine1983

Gotcha. Just a lesson from my experience though - I had a slow coolant leak for a long time, but then one day it was a big leak and I didn't know it until my engine was getting hot

I hope you figure it out!

Yeah, I'm trying to figure that one out as well. Always something. I'm quite certain its not getting into the engine, so, that's good.