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Gear box

I have 120 gear box on 35hp isuzi engine when i have been cruising for about 3 to 4 hours it will not go into forward gear after slowing down in reverse,can you HELP.

Asked by: Eddie Kingswell  | 9.56am, Wednesday 2 October

WW says:

The PRM 120 gearbox is a mechanically operated gearbox. However, it still requires oil for lubrication, so the first point to check is that the oil level is correct. Also, if the oil hasn't been changed for some time, it may be worth ensuring that this is done. You may then also find if there is any excessive metal swarf in the oil- which could point to more serious internal damage.
If the oil level is correct, move onto checking that the gear selector pushes the control on the gearbox fully against the stop in both forward and astern- failure to push the lever fully to the end can cause issues with engaging gear.
If the engine goes out of alignment with the prop shaft, this can place undue stress on the gearbox, which could, as the engine warms up, could lead to problems. However, checking alignment accurately is a job for someone with experience and the correct tools (feeler and dial gauges).
Also, check the temperature of the gearbox (with care!). If it is too hot (such that you can't touch the gearbox after it has been running for a few hours) then this may point to internal problems.
You can download an owners manual and workshop manual from the Newage Transmissions (PRM) website. However, if the above checks don't rectify the problem, it is more than likely that the gearbox may require professional attention. However, this is usually fairly easy, but does require a good working knowledge of gearboxes- and best done out of the boat.
Let us know how you get on or if we can be of any further help.

Mark Langley  | 10.21AM, Wednesday 2 October

If the oil is getting very hot, the hydraulic pump within the gearbox may not be able to get enough pressure to engage the forward clutch.
Changing the oil might help, but also look at the airflow within the engine compartment.

Rupert Smedley  | 11.25AM, Wednesday 2 October

Readers say:

ok thanks i will try these first.

Eddie Kingswell  | 8.52AM, Thursday 3 October

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