Merc 850 Thunderbolt

[jamesonm]

Just acquired a 16 foot vanguard with what I believe to be is a 1973 Merc 850 Thunderbolt.

I took the boat out and was unable to throttle up in forward, however reverse functioned normally. The boat will idle no problem and shift from neutral to forward and reverse. There is very little resistance when trying to increase throttle in forward. Reverse has more resistance.

I don't know much about boats but was wondering how I would troubleshoot this issue. The cables look like they could use replacing, I believe theyre 13 feet (give or take a couple inches).

Any help would be greatly appreciated.

James

 

[jamesonm]

I am also going through historic post related to the motor -- lots of resources.

Thanks

 

[jimmbo]

Just don’t post on a thread where the last comment is older than 4 or 5 months

Your issue could be a problem in the Control unit

 

[jamesonm]

In neutral the prop is turning fine. In reverse there is resistance when trying to turn the prop. But when in forward there is a clicking noise when turning the prop.

 

[jimmbo]

Normal. That Clicking sound is just the Clutch Dog Ratcheting.

 

[jamesonm]

I will have a read thru the following manual -- what a great resource, thanks iboat!

http://www.boatinfo.no/lib/mercury/manuals/mercury_1965-1989_40-115.html#/298

 

[jamesonm]

Can a layman install new throttle and shift cables?

 

[jimmbo]

Depends on the Layman's Mechanical Ability,and willingness to pay attention to detains

 

[jamesonm]

Perfect, I'll order new ones.

Mechanically adept here. Also love the idea of learning more about the boat in an intimate way.

 

[Snatchymanx]

I’m having a very similar problem with my 650. I’m only getting like half throttle (one in forward gear I have to push it all the way down to like 9 o clock before it even starts moving). No dead spot in reverse, and it’s not getting anywhere near full throttle.

I did new cables and rebuilt most most of my Mercontrol box.

Keep us updated if you get it fixed.

 

[jamesonm]

Finally got around to installing new cables. Will try and get it on the water tonight.

I did notice that there isn't a lot of resistance when increasing throttle, but will see what happens on the water.

Can you add resistance to throttle increase/decrease without opening the mercontrol box? Something at the linkages to the motor possibly,?

I also noticed that when in neutral the prop wants to spin very slightly in reverse direction, is that normal? It transitions between forward and reverse easily.

 

[jamesonm]

Run really well on the water woohoo! seems to be fixed.