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Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

new electric start motor

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Dan86
Navigator

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130 Posts

Initially Posted - 03/14/2005 : 22:18:55

I am purchasing the tohatsu 9.8 25 inch shaft electric start motor to replace a 20 y/o johnson pull start. I have a couple of questions;
1. Can the house battery be used to statrt the moter vs putting on a starting battery?
2. How do I wire the alternator to the battery, will it interfere with other wiring at the battery.

Sorry for the stupidity! Dan

Edited by - Dan86 on 03/14/2005 22:24:59

Dave Laux
Captain

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318 Posts

Response Posted - 03/15/2005 : 07:03:21

1. yes, I do not use two batteries.
2. The new engine will come with a positive and negative wire that connects both the starter and alternator. Just hook it up to the battery terminals and you are done.

Edited by - on

mwalkup
1st Mate

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USA
79 Posts

Response Posted - 03/15/2005 : 15:11:52

Dan,
I'm in the same boat ( literally / figuratively )

I've just received my Tohatsu 9.8 long shaft.
The cable that hooks up to the battery is number one, 7.5ft long about 3-4 ft to short to get to the battery storage area.

Number two, the cable coming off the motor are smaller gauge than a standard battery cable, and the round post type terminals are to small to fit over the battery post.

I do not want to dedicate a new starter battery to the mix,
because of the cost, and I'd like the alernator to help keep my single battery up to charge.

Just today I went to an electric supply outlet and a battery store to find a connector, called a butt-splice connector to splice another length of cable together to reach the battery.
I had planned to use this to connect the two cables, solder the cable to the connector and heat shrink a protective cover to help keep out moisture.

My question's are: is the dice and splice cable idea fesible.
What gauge size is standard coming off an electric start motor, and is it possible to use this smaller cable with a standard terminal hooked to the battery.

One of our mates here suggested installing a trolling motor connector in the cockpit, installing a new plug on the end of the motor cable, and then plugging it in.
Good idea I just don't want more stuff in the cockpit. I suppose I could install it underneath in the quarter berth area, but splicing the two cables together seemed more straight forward.

Dan I'm not sure if you'll have this same dilemma, but you might since we have the same boat and motors.

Am I just making this project to complicated.

Any suggestions please.
Mike
83 tr/fk #3528

Edited by - on

Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 03/15/2005 : 17:24:42

Mike (<i>and other elec-start OB installers</i>),

I don't suggest permanently extending the two heavy wires from the motor by splicing.

I really like the heavy duty trolling motor connector idea. You don't necessarily have to mount it out in the weather. You could put the connection inside a locker (with a notch to accommodate the motor wires), or install a thru-hull (high in the transom or cockpit) large enough for the male end of the trolling connector set to fit through.

On my 1979 C-25, I installed two terminal posts just inside the transom (a high current junction block would be just as good), and joined the motor wiring to the boat wiring there. It's a reliability/ease-of-use compromise between spliced wires and a plug.

You might also consider installing either a manual switch, fuse, or circuit breaker in one of those leads, preferably near the battery end. Ask yourself what you would do if your starter motor solenoid got stuck on (welded relay contacts/shorted starter button -- it can happen) and/or electrical smelling smoke started pouring out of your engine cowling and the insulation on those skinny starter wires started to melt...

I went with a switch, but a circuit breaker would be even better. The switch or circuit breaker has the additional minor feature that you can use it to disable the electric starter circuit when you're not aboard.

As for wire guage for the extension cables, I'd suggest you go up one size from what came with the motor. I can assure you they didn't make those leads any heavier than they had to be for the length they gave you. If you extend them significantly without going up in guage, you'll be adding a voltage drop between your battery and starter motor which will reduce cranking RPM, especially if the battery isn't at its best.

-- Leon Sisson

Edited by - on

frog0911
Master Marine Consultant

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USA
1349 Posts

Response Posted - 03/15/2005 : 22:59:23

Dan, look on page four of the General Forum and you will find a thread on connecting a electric start motor. There are some pictures included in it that will give you an idea on what the locking trolling motor plug looks like and how it is used.
I would in no way splice wires to the starter/alternater cables, just to much added resistance and chance for corrision no matter how good the splice is done. As far as wire size, 8 gauge is what the engine comes with and is plenty large enough for good current flow. If added length is needed, I would stick with 8 gauge.

Edited by - on

77Gypsy
Captain

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USA
356 Posts

Response Posted - 03/16/2005 : 00:25:55

I do have a second battery for the motor. i like it better because it is always good to have a back-up in a pinch. "connecting the house battery to the motor or the motor battery to the house"

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Dan86
Navigator

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130 Posts

Response Posted - 03/16/2005 : 07:04:04

Frog, thanks for the reference to the earlier post, I did not remember that information had already been hashed out. Good info, I will anxiously await the new motor, should be here in 2 to 3 weeks!!!!!

Edited by - on

lcharlot
Master Marine Consultant

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Antigua and Barbuda
1301 Posts

Response Posted - 03/16/2005 : 08:36:08

I recently measured the current draw for the starter on a Yamaha 9.9 : 90 amps surge, 75 amps steady-state. This suggests that a 6 ga cable would be the minimum size to prevent voltage loss. The Yamaha T8 I bought last year also came with cables that were about 4' too short to reach the boat's battery box, and I had to splice on a length of extra cable (I used 6 ga). I have read too many postings about people having corrosion problems in battery connectors that are exposed, so I ran the cable directly to the battery switch with no extra connectors. Of course, there is a downside: If I ever need to remove the motor, I'll have to cut the cable, or disassenble it from the battery switch and pull it back out through the hole in the transom. However, at 130#, this motor is so heavy, I don't plan on removing it unless absolutely necessary.

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.