Volvo Penta 8.1 gears not shifting?

mvgvb

Hi all,

We've had a 2008 280 EC with a single Volvo Penta 8.1 for 3 years now. About 600 hours on it and seemingly in good condition - has always run great.

Just got out for the first voyage of the year and opening up throttle is increasing rpm, but not translating to any mph. It pushes the bow up a bit, but didn't increase above 10kts even at full throttle.

get a bit of shaking in the engine too. 

Thinking is a gear shifting issue, but not very familiar with this. Any thoughts or recommendations?

thanks!

Dream_Inn

Depending on the props, but possibly a spun hub?

aero3113

Is your drive all the way down?

mvgvb

@Dream_Inn any easy way to test that?

@aero3113 trims working and we tried up and down no speed 

captkevin

What drive does boat have?

YYZRC

I had a similar issue and it was a spark plug wire that was off. I would start by checking plugs/wires/cap and rotor. 

mvgvb

Apparently the growth is crazy in our water right now. Any chance that amount of growth would keep us below 11kts?

aero3113

If the bottom is fouled also, it could.

mvgvb

@aero3113
@YYZRC

Any idea where the outdrive trim relays are? Scraped the props clean and now have an issue that the drive won't trim down...

aero3113

I’m not sure where on a Volvo, on a merc they’re near the trim reservoir .

YYZRC

Volvo and Merc trim pumps are basically the same setup from what I’ve seen. Maybe @echandler1971 can comment. 

echandler1971

The relays are right on the pumps on the starboard side of them. You can even swap them between each other. One thing I’ve noticed with the trim pumps in general is that the engine connector that connects up to the pump can have a sunken male end that needs to be pulled outward with needle nose pliers. In my case, it’s just one of the two leads sinks down into the connector and only one of the two leads are actually connected to the pump female connector. This has happened to me several times where I had to unplug from the engine, pull the sunken lead level with the other on the engine side connector and replug it in  

Formulaben

mvgvb said:
Just got out for the first voyage of the year and opening up throttle is increasing rpm, but not translating to any mph. It pushes the bow up a bit, but didn't increase above 10kts even at full throttle.

get a bit of shaking in the engine too. 

Apparently the growth is crazy in our water right now. Any chance that amount of growth would keep us below 11kts?

Absolutely it could, since the props will cavitate and produce very little thrust and a lot of vibration.  Hull growth will reduce overall top speed but with cavitating props you won't even get on plane.  I'd absolutely clean the props first.