345/348 - Overheating Issues with D1-30 Volvo

Overheating Issues with D1-30 Volvo

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Topic: Overheating Issues with D1-30 Volvo

Posted By: SurfinSurgeon
Subject: Overheating Issues with D1-30 Volvo
Date Posted: 29 October 2025 at 00:43

Just curious about people's experience with D1-30.

During the marine survey prior to purchasing my "new" Hanse 345 the engine overheated at less than cruising speed moving the boat over to a yard for haul out. We replaced the impeller which looked fine. A engine technician checked the inflow and ultimately said the engine was fine. While running at 2700 rpm a few weeks later we had the temperature alarm go off. My diver felt that the sail drive raw water inlet had marine growth that he cleaned but in reading the manual I learned that wide open throttle can be between 2800-3200 rpm. In addition, I was surprised the owners manual suggested that maximum sustained cruising RPMs should be 500-1000 rpm lower than WOT.

This past weekend we moved the boat 48 nautical miles and due to low winds and direction, motor sailed predominately at 2200 rpm at around 6.3 its SOG (against 0.5 California current) and at 2400-2500 could approach nearly 7kts SOG and that for short durations we could hit hull speeds around 2700 rpm which I. After 8 hours of motoring and motor sailing I am happy to say we had acceptable engine temperatures and no overheating issues.

Curious as to others experiences or issues with temperatures and rpm vs performance.

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Tom N
S/v Take Five
Hanse 345

Replies:

Posted By: sgrhma2
Date Posted: 29 October 2025 at 11:31

I had a similar problem on a Volvo MD2020, where there was intermittent overheating, but progressively becoming more frequent. Initially I blamed the impeller and growth inside the sail drive leg. What it turned out to be was the engine thermostat not opening properly. To test this, drain the engine coolant and then remove the thermostat. Put the thermostat in a saucepan covered with cold water and then place on a cooker ring and proceed to boil the water. Ideally you have a thermometer that is capable of measuring the water temperature. As the water increases in temperature you should see the thermostat open fully. The fully open temperature should match the temperature marked on the thermostat housing. If the thermostat fails to open or doesn’t open fully it needs to be replaced.

I suspect that your overheating problem is being caused by a faulty thermostat.

Hope this was useful

Simon

Posted By: SurfinSurgeon
Date Posted: 31 October 2025 at 01:55

Simon, thanks.

I do think that it was the thermostat. While I inherited a 8 year old diesel with only 83 hours - I think underuse contributed. Seems to opened up with 20-30 hours of use in the last 3 months.

Appreciate your comments. 8 hours of 2200-2400 rpm worked well with good temps.

Tom

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Tom N
S/v Take Five
Hanse 345

Posted By: Fendant
Date Posted: 22 November 2025 at 05:02

Tom, I had an overheating issue on my D1-30. It occured in a total calm when motoring

back to shore at 2000 rpm ( which give me 6 real knots ).

Root cause was missing coolant, so check the level in the reservoir.

I had never noticed any colored fluid in the engine room, when checking oil.

The mech filled the coolant and finally saw a extremely low wate drops. The it came from a tiny crack in the pump housing for the inner circuit. Volvo Europe said that they never had a defective pump, so no spares available. We finally sourced a replacement through VP America.

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Frank

Posted By: Ratbasher
Date Posted: 22 November 2025 at 07:40

I had an unusual overheating issue with my Yanmar at the start of the season. The alarm sounded after 30 minutes operation despite a good flow from the exhaust, an intact working impellor and functional thermostat indicating that the problem was in the fresh-water side of the system.

Over the winter I'd had a mechanic strip and clean the entire cooling system so I wasn't best pleased. However, in my enthusiasm to get out I'd simply checked that the expansion bottle was filled to the correct level and failed to take the cap off the header tank to check the level - which if I'd done would have shown no coolant. It turned out that when the mechanic re-filled the system he failed to add the extra amount needed to fill the calorifier, also failing to 'burp' the system before doing a final check on the correct level. The extra amount needed to fill the calorifier was 2.5ltrs.

Despite the negligence of the mechanic the responsibility remained mine as I'd failed to do a proper check; I'd assumed that because the expansion tank was full then the coolant levels were OK but this isn't necessarily the case. Thankfully, no harm was done but another lesson was learned a harder way.

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H400 (2008) 'Wight Leopard' Gosport, UK

Posted By: SurfinSurgeon
Date Posted: 29 November 2025 at 15:42

Well my overheating issues reappeared last weekend. And ended up with no flow water out exhaust.

I pretty much ran my entire raw water system short of pulling out heat exchanger.

- checked strainer

- checked impeller and confirmed free flow upstream of heat exchanger

- "sounded" all the holes in the heat exchanger (there was some gummy residue in about a 1/3 of them

- checked the end caps of heat exchanger

- removed exhaust elbow that had massive amount of carbon build up and cleaned it (THIS WAS THE PROBLEM)

Now I have excellent water flow. I plan to replace exhaust elbow with a stainless steel after market exhaust elbow.

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Tom N
S/v Take Five
Hanse 345