New Motor to Me

After looking for a while, I found a good deal on a mid 80's johnson 8hp to put on the back on a 12 foot aluminum bow boat - it is rated for up to 12, but the trick is - 2 questions.

1. What do I go over on the motor to get it all tuned up?
2. The shaft lenght of the motor is 17.5, but the transom if 15. How much will that affect performance?

Re: New Motor to Me

film495 said:

After looking for a while, I found a good deal on a mid 80's johnson 8hp to put on the back on a 12 foot aluminum bow boat - it is rated for up to 12, but the trick is - 2 questions.

1. What do I go over on the motor to get it all tuned up?
2. The shaft lenght of the motor is 17.5, but the transom if 15. How much will that affect performance?

Click to expand...

1. carbs rebuild, water pump, spark plugs and wires, check the compression to have an idea where your standing, new fuel, fuel filter.... go from there... ohh yeah cheange the lower unit oil...

2. theres going to be a lot of drag thats going to affect performance, which could be considerable ... can you raise the motor? maybe install a bracket...

good luck

Re: New Motor to Me

film495,
How's it running?
If it's running good, I would leave the engine alone.
Just change the impeller and lube.

Re: New Motor to Me

Well, I knew the previous owner - so, I'm pretty sure there aren't any immediate issues to keep me from running it a little, so - I just checked the lower unit oil - and have run it a few times. It actually seems to go pretty good - it is on a small 12 foot row boat, but gets up on plane and I would guess goes about 15mph with me 280 lbs in the back, and 2 cinder blocks in the bow to balance the load. So, this is how it seems to perform -

Jumps right up on plane and then seems to peak speed at about 8mph and seems like that is all the motor has, then I shift my weight forward about 2 feet to get the bow down(I call this manual trim) and it gets up to an estimated 12 mph - then when I shift my weight back again - there is more speed and RPM left in the motor and it gets up to around 15mph - I'm zipping right along up on plane - so, I'm not sure the performance benefit I'll get would justify the work of raising the motor a couple inches? I'm pretty happy with it, but if I could get even more out of the motor I'd consider a solution to raise the motor.

Re: New Motor to Me

Normally I would (and generally still do) agree with countvlad. Given the information you gave after regarding how it's running now, I would change the lower unit oil, put in a new impeller and check the fuel pump screen for cleanliness. Other than that, I would not touch a thing. Your getting the best it has to give out of it now. Why monkey with that. Best of luck. Rick.

Re: New Motor to Me

i think you motor may be older than you think, what is the model #. 17 1/2 shaft was older motor lengths.