Problematic Honda BF75A gearshift

[Don Mackay]

Honda BF75A gearshift problem

My 1999 model 4-stroke Honda BF75A developed gearshift problems last.season. Started with gear crunching while out fishing, so I limped home on auxiliary engine. I have since renewed the Honda control unit in cabin, the gear cable and all external gear linkages and checked that the gearbox itself is ok. On this model the gear change is transferred from the external linkages outside the powerhead horizontally through the powerhead innards before a final internal linkage transfers the change downward to the gearbox. I can operate gear selection manually so I know all linkages are fine. I can set the gears fine in harbour, take her out on the water, run through some gear changes, and she performs fine for a short while, and then the gear crunching and gear jumping starts inexplicably again This problem starts when the powerhead reaches operating temperature , but why? Has anyone experienced this problem, and what did you do to resolve it?

Thanks

Don

[J.W.W.]

Hi Don,
I'll try to help you, but my english is not the best, so sorry for that in advance

If you are perfectly sure that your engine doesn't have any problems, while shifting manually with the cables disconnected, there probably is to much "play" in the complete mechanics together.

Reasons for that can be found in either the remote controll, but most of the time in worn shift & throttle cables. Don't buy new Ultraflex or Honda for that. Quicksilver (mercury) has a set of very fine & precise "platinum" cables in their assortiment which solve most of those problems forever. Please don't invest your money in them exepsive cables before you're absolutely sure that: 1. There is no play in the mechanics of your remote. 2. Your engine shifts properly without remote controll cables attached.

If you're engine appears to have problems too with the shift cable disconnected, the problem will probably be in your gearcase. Most of the time you're dealing with worn gear-cams (don't know if I translated this properly). I mean the little blocks on the gears which grab the shifting clutch when shifting. They quickly get "round edges" when shifting mechanics are not properly set. Seeing them edges with your eyes, does make you think that that's not the problem, but an experienced dealer can tell you if their worn or not in one look.

In that case your gearcase has to be opened to check. When you don't have experience with this, please see your dealer for this..

Good luck solving the problem!
Regard Wouter (NL)

[9D280]

JWW - for someone who doesn't speak english, that was pretty d@mn good.

Don,

A few more diagnostics questions: Apologies if they are a bit specific and may seem to repeat - it's all part of the diagnosis!

Once you have engaged in harbour, I can read into your text that either you can drop in & out of gear in the harbour then it goes pear shaped outside, or that yo ucan play around outside for a bit before it starts. (or both?) Can you confirm?

On a similar theme, will it run for ages at low throttle but jump out of gear when you open up? Or does it only jump out at certain RPM?

How do you normally engage gear? Sharply or do you let it "dunc-dunk- dunK- CLUNK into gear? (of course if it's a secondhand engine you have the problem of not knowing how the previous owner did it)

The fact you have changed everything, if you disconnect at the engine end and try to wiggle the end of the cable in & out, how much play is there?

Am I reading this right that your gearshift is on the side of the engine a bit like a 4 or 6 HP tiller control machine? Is the cable connected by a "t-pin" through a slotted hole? Those pins sdo wear out eventually (check for movement between cable end & lever as you change gear) , but I am a bit surprised at that kind of arrangement on an engine of that size & vintage.


The other thing I was going to suggest was the bushes in the remotes (mine were starting to suffer from that) but as you say you have renewed the remotes, I gess that is removed from the potential fault list.


For what it's worth our old 1972 Johnsorude suffered a very similar problem - when we dissmantled the gearbox the leading edge of the dog' teeth (the teeth that engage the gears to the shaft) was battered to a nice 30 degree angle - open the throttle and it pushed itself back out of gear. That was on a tiller control, so virtually nothing holding it from jumping back out. If that is the problem, yours wil lhave the gear cable trying to hold it in, which is why you are getting crunching instead of a jump.

Do this test in clear water - disconnect the gear cable at the engine. Try to engage gear form the lever - if it seems to need a push over a hill to get it in read response 1) If it smoothly slides in, response 2
Basically engage gear & open the throttle.
1) If it jumps straight out then gubbed dog teeth is most likely your problem.
2) If there is some instant crunching that won't go away if you throttle back, see 1.
3) If nothing happens other than you drive off and take the next "best wake shot" photo your gearbox is fine, and it's time to look at the linkage.


Let us know.....

[Chris]

I would disconnect the cables and then manually shift to test once out on the water and up to temperature.

There are further adjustments that can be made with the shift rod that goes down the leg into the top of the gearcase. In order to ensure this rod is set right you will need to remove the gearcase from the leg and then check the height of the shift rod is set correctly. This process and the correct settings should be provided in the workshop manual.

If all this is correct and you still have shifting problems then it will probably be time to get the wallet out..

I am assuming you have drained the oil in the gearbox to check for water ingress and bits of metal in the oil?

[wiLlfish]

Originally Posted by J.W.W.

Hi Don,
I'll try to help you, but my english is not the best, ..........................................

itts de duch ekwivalent to dat scoch bastud jw butt wiv a ekstra w

bowt az lorng windid az wel

orl hee ad too saiy was

dogg cluch


butt wivowt showtin

an downt gett dogg cluch mixt upp wiv duch clogg.

[Burtox]

All the questions asked are relevent you need to work out whether the controls are throwing the gear in far enough. Once this has been eliminated you will need to explore the gearbox.

Don't worry its not too bad

Ive got a Honda BF90 which is the same as the 75 and I had a worn out dog clutch. I managed to change it with a few make shift tools.

Below is a photo of my worn out parts as you can see the edge of the dog clutch has rounded off on the reverse side.

[clydeoutboards]

Hi

we are in Gourock and Honda dealers and have a mobile service. shame I did not see your post yesterday I was on queen street in Helensburgh and cameron was in balloch! Anyway please just give us a call and we will get you sorted.

Cheers

Dave

[Don Mackay]

Thanks guys for taking the trouble to offer your thoughts .... there is plenty for me to think about and test out ... your advice is really helpful ...get back to you soon with how I get on.
Regards

Don