Frankenstein rejects the zap

[sea-bee]

I've made a Frankenstein, but have a problem. It started life as a Yamaha outboard, an electric start FT9.9 with the extra long leg and high thrust gearbox. It came to me real cheap with a blown power head. I have renewed this with a transplant. I have taken the powerhead off a new 15hp Chinese copy of the short shaft manual start version, and used that engine as part of the rebuilt the Yamaha.

It starts fine with the manual rope start, and all is good. Except when hooked up to the starter motor. The motor spins ok, but no spark. Rope pull, and it starts easily.

Any suggestions for what might be wrong?

[paulajayne]

Is the electric start bringing the ignition circuit on?
Is the electric start pulling so much power that the HT coil is not getting sufficient power?
Try it with a couple of batteries in parallel to start it, if that works then bigger start battery required.

[belizesailor]

Or, is there something thats not wired properly, for example does the ignition switch provide power to everything it is supposed too (starter AND ignition pack for example). Or, is there a ground fault associated with the ignition/starter circuit so that spark is diminished.

Upside is that for a 9.9-15hp you dont really need an electric start.

[GILow]

Might sound like a crazy question.... But is the starter spinning the motor in the correct direction?


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[Cadence]

Sounds like a you were very inventive cobbling that together. I cannot think of a thing.
I doubt the starter is drawing too much juice since it starts by the pull start, no battery required.
GILow's question does not sound that crazy. Maybe swap the + and - to the starter.


Sometimes the simplest things are overlooked.


Let us know.

[dmalcol1]

Great idea I have old Yamaha t9.9 with dead power head. Can you tell me take off model that you used to replace engine.

Thanks

Remove plugs and check for spark when cranked

[belizesailor]

Sea-bee, you put a 15hp power head on a 9.9 body...did you check any of the specs of the drive train to see if it would handle 15hp.

I ask because I looked at doing something similar. It could be done easily physically, but I checked the dimensions of some key compoments and they were different.

[Cadence]

Originally Posted by belizesailor

Sea-bee, you put a 15hp power head on a 9.9 body...did you check any of the specs of the drive train to see if it would handle 15hp.

I ask because I looked at doing something similar. It could be done easily physically, but I checked the dimensions of some key compoments and they were different.

That is probably a non issue since most factory 15s seem to be hopped up 9.9s.

[belizesailor]

Originally Posted by Cadence

That is probably a non issue since most factory 15s seem to be hopped up 9.9s.

Could be, dont know in this case. Some, like Tohatsu, take a signficant weight jump above 9.9. My understanding in their case is that the 9.9 is actually a hopped up smaller engine and after that they go to larger and heavier components.

[MarkSF]

Originally Posted by sea-bee

I've made a Frankenstein, but have a problem. It started life as a Yamaha outboard, an electric start FT9.9 with the extra long leg and high thrust gearbox. It came to me real cheap with a blown power head. I have renewed this with a transplant. I have taken the powerhead off a new 15hp Chinese copy of the short shaft manual start version, and used that engine as part of the rebuilt the Yamaha.

It starts fine with the manual rope start, and all is good. Except when hooked up to the starter motor. The motor spins ok, but no spark. Rope pull, and it starts easily.

Any suggestions for what might be wrong?

What you have made is a "Frankenstein's Monster". Frankenstein was the creator, not the monster.

[sea-bee]

I am making new battery cables for the monster, and will try it again. I think they were too small and maybe that is the problem.

The original motor is one of the old model T9.9's with the larger capacity powerhead. A few years ago, Yamaha "upgraded" the model and now use a souped up 8hp motor. While it is lighter, I have read reported that it doesn't have the grunt of the old ones. That original size Yamaha powerhead is now on the 15hp motors.

The replacement motor is a Parsun. This is an identical copy in every respect. I haven't found any parts that are not interchangable. I have used the Japanese parts where ever possible, but if they were too old, swapped them for the Chinese parts. Try putting some bolts in a vice and snap them off with a torque wrench and you'll know why. In the same size, try a Chinese, a Japanese and a German bolt and compare.

[MarkSF]

Genuinedealz.com make really nice battery cables to order. Just a thought.... and their prices are pretty good.

[sea-bee]

The new battery cables fixed it. This surprised me, as the old cables were still able to spin the motor over fast enough, but no spark.

Further on the interchangability parts, I found that the choke spindles on the Parsun and Yamaha can be swapped. The electric Yamaha spindle had an extra fitting on the inboard end allowing a solenoid to close the choke. I was able to swap the shafts and connect the electric choke actuator.

It's all running nicely in a drum, and is now ready to go on the boat.

[Cadence]

Originally Posted by sea-bee

The new battery cables fixed it. This surprised me, as the old cables were still able to spin the motor over fast enough, but no spark.

Further on the interchangability parts, I found that the choke spindles on the Parsun and Yamaha can be swapped. The electric Yamaha spindle had an extra fitting on the inboard end allowing a solenoid to close the choke. I was able to swap the shafts and connect the electric choke actuator.

It's all running nicely in a drum, and is now ready to go on the boat.

Grats Dr. Frankenstein. A lot of innovative thinking. Just for shits and giggles, what do you have invested in it?

[sea-bee]

For the pair of the blown Yamaha motors, I payed $400. For the 15 Parsun, another $2200. That's about half the cost of the new FT9.9 here in Oz. On top of that was the time to strip two motors and put one back together; probably two full days in total. I had a good mechanical knowledge before hand. I used to pull my old air cooled beetle apart and put it back together on a regular basis. Plus the mechanic that sold me the Parsun was more than helpful, assisting with heat torch on parts of the Yamaha, sourcing parts and providing information.

On the plus side of the time investment, I now know a lot more about outboard motors.