New '78 15hp

[dodgeramsst2003]

Hi all,

Found this forum while searching for info on my new purchase. I picked up a 78 15hp short shaft for $400 off craigslist today. My neighbor has an older 9.5 that he really likes so I figured I couldn't go wrong. Can anyone who has or had one of these models give any advice? quirks? things to watch for etc? This is going to be a kicker motor for my 22ft Century Hardtop so I think I'll have plenty of power. I've been boating for about 15 yrs now so I'm not new to that, except for the first boat, they've all been I/Os. Thanks,

Chris

 

[HighTrim]

Re: New '78 15hp

Welcome to iboats.

As you probably know, if you take care of the outboard the outboard will take care of you.

Being new to you, I would check the water pump and install a new impeller. Inspect the plugs and replace as needed, and check compression to use as a benchmark for future troubleshooting. Take her for a rip and see how she does.

Good luck with her.

 

[Boatist]

Re: New '78 15hp

First buy a Johnson manual for the 15 hp. Well worth the investment.
I have a 15 HP 1975 Johnson I use for a kicker on a 21 foot aluminum boat.
If it is a short shaft convert to a 20 or 25 inch shaft especially if your a saltwater boater.
My motor barely has enough power to turn into the wind and sea when offshore with 8 foot swells and 30 MPH winds. Your boat might work better.
My boat is aluminum so wind will blow the bow to the side fairly fast and motor has a hard time of getting ahead of it.

I would suggest put it on muff and take the cover off and check the temperature. Should run about 140 degrees F, so can put a finger on the top of the block for about 4 seconds before pain. If you have a inferred temperature gun again should be about 140 when the thermostat opens and hot water comes out of the the water output holes.

I not sure if the 78 has the p tail water pump pressure indicator or not. If it does not then the water will spit out the 3/8 inch hole at back of the engine just under the hood latch. Usually will get no water or spray on muffs but on the water or in a barrel where you have some back pressure will get some spray.

My thermostat has failed at least 3 times and every time stuck open and the motor ran cold. I boat a lot in the Pacific Ocean.

I would suggest to get a new set of spark plugs and do a Decarb first chance you get. After complete and have run for a while change the spark plugs.

I belive the best prop for you as a kicker will be a High thrust prop. I have been useing a 10 inch by 9 pitch by 4 blade but it too much pitch for my boat so am going to buy a 10 inch by 7 pitch by 4 blade high thrust prop.

The one I have backs up great and good in foward to about 4 MPH but wide open the engine will load up and stall.

I would also remove the prop and make sure the prop shaft has so grease on it. Pull the lower and upper plugs on lower unit and drain water into a pan to see if any water in the lower unit. Then ofcourse refill from the lower plug until oil comes out the upper hole. Then put the upper plug back and remove the fill tube from the lower plug and install the lower plug.