Dual johnson 6hp outboard on boat

[danielvanalphen]

Hi guys, I have a 14 ft aluminium v hull which I use on my local lake. I run it with a 1977 johnson 6hp, I get up to 15 kph (9mph). I also have a 1966 johnson 6hp that runs perfect. I was wondering whether if I mounted both engines on the transom and ran them would I in theory double my speed?. The transom is strong enough as I've added steel bar support when redoing it. Would this be something that would be worth trying or is it just a disaster waiting to happen?

 

[racerone]

Well-----It can and has been done.-----You will NOT double the speed.----You will go a faster , but not 29 kph.

 

[tpenfield]

In theory . . . Change in speed is not a linear relationship to change in power. Power = Force x Velocity

Doubling the power may get about a 30% increase in speed. If the boat has a fairly flat bottom towards the stern, it may help.

 

[danielvanalphen]

Well-----It can and has been done.-----You will NOT double the speed.----You will go a faster , but not 29 kph.

So do you think it would be worth trying to do or is it just a waste of time? Appreciate the reply

 

[racerone]

If you have the motors then go for it.----Use your phone for determining the speed you get ( 21 / 22 kph ) and post it here.

 

[jbcurt00]

The steel bar shouldn't be necessary unless you plan to overpower the boat which isn't advisable.

Why was it added?

 

[3rdtimesthecharm]

Don’t let them over-rev.

 

[danielvanalphen]

The steel bar shouldn't be necessary unless you plan to overpower the boat which isn't advisable.

Why was it added?

The boat was my grandads boat and is about 60 years old. It sat outside for 20 years so i had to re male the transom using fiberglass and marine plywood. It was just a back up as before the transom was non existent and I just wanted to be safer than sorry

 

[danielvanalphen]

Don’t let them over-rev.

Yeah that's one of my concerns, but like most people who run older outboards they are aware of the sound of the optimal rpm so I'll just try to slowly run up the rpms to what I think is normal and see not go over

 

[jbcurt00]

The boat was my grandads boat and is about 60 years old. It sat outside for 20 years so i had to re male the transom using fiberglass and marine plywood. It was just a back up as before the transom was non existent and I just wanted to be safer than sorry

Should remove the steel, it's caustic to aluminum and could cause corrosion problems. Lots of pinhole topics posted @iboats some repairable, some not salvageable...

Even if not evident yet,