Volvo Penta trim cylinders: 3860881, 872837, and 854695

This is the third generation of hydraulic cylinders of the Aquamatic series, replacing the older ones with the fork-like rod. This family of cylinders was launched under reference 854695, and its first application was on the SP-C drive, which was regularly combined with the MD31A engine. The second revision was published with trim cylinder 872837, and it is very common among DP-C, DP-D, and DP-S drives. The last revision, and currently active part number, is 3860881, and was installed to the latest DuoProp drives, like the DP-G and the DP-E. All of these trim cylinders are considered non-serviceable components, which should be recycled when their lifecycle ends. This usually happens when one of the following failures occurs:

• The trim cylinder leaks hydraulic oil from the pressure seal of the cap.

• The trim cylinder cannot maintain the pressure within the cylinder and moves slowly from the “UP” position to the “DOWN”.

• The trim cylinder rod has formed a groove at a specific length, and hydraulic oil leaks from there.

• The threads of the hoses are damaged due to cross-threading.

Of course, a trim cylinder unit is a very expensive element, so Poseidon Marine reverse-engineered its consumable parts in order to make them serviceable and extend their lifecycle. Although we managed to create a less costly solution, new problems came up; the threads of these trim cylinders are not the same, nor is it classified under specific drive serial numbers. Our ten-plus years of experience in this sector, as well as the documentation of fitting issues, and the constant feedback flow with our customers, have led us to the following conclusions:

• The trim cylinders of this family are usually with a metric thread (M40 X1.5). When this happens, the thread of the trim cylinder rod is also metric (M10X1.5).

• When the thread of the cap is imperial  (1-9/16”  5/16"-18 UNC), the thread of the rod is also imperial (⅜ UNC).

Although this is not serial-number-defined, we have observed this fact on drives after DP-D, which are usually DP-E and DP-G. Until recently, in order to bypass this issue, we would supply the flat-bottom cap of the previous generation of cylinders “872612”, which is by default imperial. For a trim cylinder rod, we would also provide a metric one. Its bolt is larger by some tenths of a millimeter, so the piston’s bore requires some polishing (3/10 mm) , in order to accommodate a metric bolt. All these modifications are no longer needed, since Poseidon Marine has created a round-terminal rod with a UNC thread, as well as an imperial cap with the proper channel at the bottom, to accommodate the recess spring. 

• PoseidonMarine® Trim Cylinder Rod Volvo Penta trim cylinder 3860881 ⅜ UNC

• PoseidonMarine® Trim Cylinder Rebuild kit Volvo Penta cylinder 3860881 imperial 1-9/16”  5/16"-18 UNC

Due to the reasons mentioned above, we strongly recommend that owners of DP-E and DP-G drives measure their cylinder threads. The easiest way is to measure over the threads, as in the picture below.

Besides the thread of the trim cylinder cap, the thread of the rod is also affected between metric and imperial cylinders. Although we supply rods with bolts, the imperial piston has a slightly smaller hole (9.73 mm), while the metric is 10.26 mm. Consequently, an M10 bolt will not pass through the piston of an imperial cylinder. Therefore, we advise you to be careful when choosing these components. 

An imperial piston on the left, compared to a metric piston on the right.

The trim cylinders 3860881 are secured onto the transom plate with the pin 872382 (№9). Between the flange screw 853060 (№11) and the pin, an insulating O-ring 925053 (№10) and a spacer washer 853059 (№12) are placed. In order to renew the seals or change the rod, this side of the cylinders (transom side) is not required to be dismounted, unless of course, further work is required on the cylinder housing. On the other side, the trim rod is secured on the outdrive with a clevis pin 872126 (№13), and a split pin 967707 (№14). By removing the split pin 967707 and pulling away the clevis pin 872126, you will free the rod. This is the right side to remove if you need to dismount the cap and access the piston in order to reseal the cylinder 3860881.

The hydraulic oil is transmitted through 2 flexible hoses, coming from the pump. The hydraulic hose 873228 (№4) is connected on the inner side of the starboard cylinder, on the thread close to the transom side. The other flexible hose with part number 873229 (№6), which is coming from the pump, is connected to the thread opposite to the previous hose. Part numbers №5 and №7 describe the same part number, 960214, which is an insulating O-ring. The interconnection between the two trim cylinders 3860881 is made with two steel pipes. The lower one has part number 854696 (№2) and must be fitted onto the outer threads of the cylinder. The upper pipe (rod’s side) part number is 854697 (№3) and is fitted again on the outer threads. There will be two threads to which no hose is connected, and they are located on the port’s side cylinder. Their reference is 852879 (№8). The trim cylinders are grounded with the cable and hardware kit 854625 (№15).

Considering the fact that you cannot check the thread of the cylinder by inspecting its outer elements, the safest way is to first remove the cylinder gland. We do offer the right tool for this job: “PoseidonMarine® Trim Cylinder tool wrench nut removal Volvo Penta 872612 3860881 19876”.

As soon as you dismantle the trim cylinder cap, you will be able to inspect the thread. Summarizing all the text above, if your old cap measures over the threads 39.47 mm (+/- 0.1 mm) then your cylinder is imperial, and you will need the following components:

• PoseidonMarine® Trim Cylinder Rod Volvo Penta trim cylinder 3860881 ⅜ UNC

• PoseidonMarine® Trim Cylinder Rebuild kit Volvo Penta cylinder 3860881 imperial 1-9/16”  5/16"-18 UNC

If, on the other hand, your old cap measures 39.85 mm over the threads (+/- 0.1 mm), then your cylinder is metric, and the parts you will need are as follows:

• PoseidonMarine® Trim Cylinder Rod Volvo Penta trim cylinder 3860881 metric M10 X 1.5

• PoseidonMarine® Trim Cylinder Rebuild kit Volvo Penta cylinder 3860881 metric

Besides the aforementioned parts, all other components between the metric and the imperial cylinders are interchangeable. The seal kit:

“PoseidonMarine® Seal kit power trim Volvo Penta hydraulic cylinder 3860881 872612”, is used on both types of cylinders.