Crispy, Hard and Smoking.

IMG_0331We had just left Kingston Marina and were motoring east past the scenic Kingston waterfront to begin the trip back to Toronto.  I headed down into the boat for some reason (stereo? chart? sunglasses?) when I heard a very faint high-pitched whine for a couple of seconds. I dismissed the noise but immediately began to smell something burning.

As every sailor soon learns,  ignore unusual sounds, smells, or vibrations on a boat at your peril. If the noise didn’t trigger a response in me,  the smell certainly got me busy.

I lifted the step and peeked into the engine compartment and didn’t see anything amiss – no flames, no billowing smoke. I took a second look and realized that the alternator wasn’t turning but the belt wasn’t broken.  Alt seizure? I immediately shut the engine down to take stock of what was happening. It turns out the belt was toast, literally.  It was crisp,  hard and smoking. It was so worn out that it wouldn’t turn or flex.

I think the noise was the alt spinning down.

I did a quick replacement as we slowly drifted towards the rocky shore,  past a few sailing dinghy’s and stand up paddlers.  I  put on a Genuine Yanmar 25132-003700 (old part no# 128670-77350). We were back up running in 5 min, I think Rufus was impressed.

Belts Belts

I need to restock my belt supply and am looking at cog belts as I’ve read they might last longer. The last belt lasted two seasons, not bad considering we did a fair amount of motoring, up the Rideau and back and the 1000 islands,  but not exactly long performance. The 80/100 alt is surely putting a strain on the belts and this reminds me that I really should track engine hours more closely.

I found favourable reviews from these two cogged belts found on forums:

  • Gates Extra Service, No 6469 EXL AVX 13x975mm La
  • Gates 6218MC (950x10mm)

It seems the above belts are automotive, fitting Audi amongst other cars.

The Yanmar 25132-003700 package says  V-Belt A37 on it.

Dayco top-cog belts received top reviews on Cruisers Forum

Understanding the Part Number

A The A stands for an “A” section v-belt.  This is considered a “Classic” v-belt style that has a top width of ½ (0.5) inches and a thickness of 5/16 (0.312) inches.

37– 37 inches is the inside circumference of the belt.  For A-section v-belts, the outside circumference is found by adding 2 inches to the inside length of the belt.  So, the outside circumference of the A37 belt is 39 inches (37+2).

On the Gates website I find the:

  • AX37 -Tri-Power(cog): 991mm, 39″ (9012-2037?)
  • A37 – Hi-Power II:  991mm, 39″

I’m confused by the length difference in the Automotive belts above and the A37 designation. Is there really 2 inches of play available?Upon inspection is seems that as long as I don’t run out of adjustment play it really doesn’t matter how long the belt is as the crucial measurement is the A

I’m also going to clean up the inner surface of my pulleys in the spring.


UPDATE – April 2017

Have ordered cogged belts for alt and water pump from Motion Canada – will update on fitting and performance.

Parts reference: http://www.marinepartsexpress.com/yanmarpartref.html

From Yachting & Boating World Forum for the Yanmar 3GM30F
Engine Oil Filter: Cooper Z1142, Fram PH6811, Solid Ace H102003 Knecht OC115.
Water Pump Impeller: Has keyway (not screw) Johnson 827, Yanmar 23007-4133 (?) Jabsco 22799-0001B
W/Pump Belt: 482 x 10 (Yanmar 104511-78780)
Alternator Belt: L 970 cm x W13 mm. Yanmar 25132-003700, Gates 6218MC (950×10)
Fuel Filter: Yanmar 104500-55710. AC Delco GF771.
Coopers FSM4110. In-Line Filters FBW-PF937. UFI 2667200.
Air Filter: Yanmar 128270-12540.


Update # 2 – May 11, 2017

Spring launch: fitted the cogged Gates AX 37 TRI-POWER® Belt (9012-2037). The 37″ belt was a bit too long as the alt was pushed out to almost the max of the adjustment, the alt itself was pushing into the silver foam soundproofing.  So next set will be 36″. It seems there is great variety in actual belt size as the Yanmar part is listed as a 37″

One thought on “Crispy, Hard and Smoking.

Leave a Reply

Your email address will not be published. Required fields are marked *