What Size motor for 17ft Aluminum

[Whidbeyboater]

I have a 17 ft Aluminum side console I am working to restore. Its a pretty lite boat but its rated for 7 people or 1750 lbs (which seems high).

The boat will be used primarily on the Puget sound for Crabbing and salmon fishing. I will also probably take it on some longer trips to the islands and overnight camping and some lakes.

It is rated for up to 65 hp. It came with a early 80s Johnson 60 hp. I am not sure on the condition yet but I plan on getting it running and using it for a while. I would like to eventually switch over to a 4 stroke. I do like the idea of having extra power on hand and do enjoy going fast when conditions permit. I am thinking the 60 will scoot it along quite well.

I know hp ratings can be kind of misleading. In general are all 60 hp engines created equal? Would a well running old 60 hp be comparable to a new 60 hp? How would a modern 50 hp 4 stroke compare to my old 60 hp 2 stroke? I am thinking the minimum I would put on it would be a 40 hp. 50 hp seems like a good middle ground for power and weight. 60 hp would be nice but might be more engine than I really need on this boat.

Any thoughts or advice would be appreciated.

Pics of the boat before restoration

 

[mbullen]

The 'HP Capacity' is based on the boat's construction and the transom's ability to absorb torque and force.
The factory engineers make that call.
Anything in the neighborhood of the max rating is going to be comparable (unless your insurance company objects).

The weight of a motor falls under 'Weight Capacity' and is part of the total weight including motor, fuel, people, and gear.
This is a formula based on displacement.
The balance of is up to you.
Relocating gear and passengers for better planing is trial and error.
If you choose a heavier motor -and since the motor can't be relocated- you'll have less to work with up front.

 

[Whidbeyboater]

The 'HP Capacity' is based on the boat's construction and the transom's ability to absorb torque and force.
The factory engineers make that call.
Anything in the neighborhood of the max rating is going to be comparable (unless your insurance company objects).

The weight of a motor falls under 'Weight Capacity' and is part of the total weight including motor, fuel, people, and gear.
This is a formula based on displacement.
The balance of is up to you.
Relocating gear and passengers for better planing is trial and error.
If you choose a heavier motor -and since the motor can't be relocated- you'll have less to work with up front.

Is it safe to assume the weight rating is as the boat came from the factory? With floors, console, seats etc? Or would the rating be for the hull only?

I just double checked and the rating is "1600 lbs persons Motor & Gear" 7 people max.

Engine is ~220 + 12 gallons of fuel ~90 lbs + extra gear coolers beer and random stuff 400 lbs. Max = 710 lbs that still gives me 890 lbs for passengers, assuming my floors and interior don't count against in my weight capacity.

I don't know how this boat came out of the factory but I assume what I am doing to it has a similar weight as it did originally. Maybe 100 heavier as I am using 3/4" ply

I don't think I want to go any heavier than 220 for my engine. The Honda BF50 is 215 lbs I think that would be perfect for this boat.

 

[Crazyboat]

HP is HP as far as I'm concerned. As long as it's measured at the same point, "Crankshaft vs Prop". The industry is kept to a 10% range, so a 60 HP could produce as few as 54 or as much as 66 ponies. Short of doing a dyno test you'll have to seek out what engines are considered "Strong" engines. An example would be todays Yamaha F150, they are considered "strong" for their rating.

Personally, I think I'd take the engine it came with and have her rebuilt. assuming you can find a topflight shop. If I recall Johson produced some 65 and 70 HP engines from the same mold.

 

[Whidbeyboater]

HP is HP as far as I'm concerned. As long as it's measured at the same point, "Crankshaft vs Prop". The industry is kept to a 10% range, so a 60 HP could produce as few as 54 or as much as 66 ponies. Short of doing a dyno test you'll have to seek out what engines are considered "Strong" engines. An example would be todays Yamaha F150, they are considered "strong" for their rating.

Personally, I think I'd take the engine it came with and have her rebuilt. assuming you can find a topflight shop. If I recall Johson produced some 65 and 70 HP engines from the same mold.

I am really hoping the current engine is in good shape. It apparently ran well 14 years ago when it was parked and I know the person that sold it too me so I know its not total BS.

If it runs good I really have no reason to shell out the money for a new motor. As much as I like the smell of my 2 stroke dirt bike I don't appreciate it the same way in a boat. Ill be interested to see how this one does. If I can tolerate the noise and fumes I will definitely keep it and consider a rebuild if it needs it.

I have heard pretty good things about these pre VRO Johnsons.

 

[mbullen]

Is it safe to assume the weight rating is as the boat came from the factory? With floors, console, seats etc? Or would the rating be for the hull only?

I just double checked and the rating is "1600 lbs persons Motor & Gear" 7 people max.

Engine is ~220 + 12 gallons of fuel ~90 lbs + extra gear coolers beer and random stuff 400 lbs. Max = 710 lbs that still gives me 890 lbs for passengers, assuming my floors and interior don't count against in my weight capacity.

I don't know how this boat came out of the factory but I assume what I am doing to it has a similar weight as it did originally. Maybe 100 heavier as I am using 3/4" ply

I don't think I want to go any heavier than 220 for my engine. The Honda BF50 is 215 lbs I think that would be perfect for this boat.

yes, the formula is roughly 12.5lbs per cubic foot of interior volume.
If floors and consoles came from the factory, that was already eliminated as accessible volume.

Also, it's best to run a compression check on the current motor before jumping to 'rebuild'.
Old 2-strokes rarely have to be rebuilt unless there was a catastrophic failure like a broken rod. Sometimes a broken ring will warrant a rebuild, but that will show on the compression check.
Even a large percentage of 'seized' motors are just corrosion-stuck and able to be worked free with the right soak.
Most of the time, it's just a matter of replacing the consumables.

 

[Whidbeyboater]

yes, the formula is roughly 12.5lbs per cubic foot of interior volume.
If floors and consoles came from the factory, that was already eliminated as accessible volume.

Also, it's best to run a compression check on the current motor before jumping to 'rebuild'.
Old 2-strokes rarely have to be rebuilt unless there was a catastrophic failure like a broken rod. Sometimes a broken ring will warrant a rebuild, but that will show on the compression check.
Even a large percentage of 'seized' motors are just corrosion-stuck and able to be worked free with the right soak.
Most of the time, it's just a matter of replacing the consumables.

Good to know. Its an old boat and I suspect it was rebuilt one time before I got my hands on it. But I think my build will be pretty close to what it had coming out of the factory.

I will definitely be doing a compression check before even trying to fire it up. Turning it by hand it at least has some compression. Its sitting on its side on a cart in the corner of my garage until I get my Transom back together. As long as compression checks out I will do carb cleaning, fuel pump, fuel filter spark plugs, water pump, lower unit oil. Not sure of anything else I should do on an engine that has been sitting for 14 years. Are there lower unit seals I should consider replacing? I haven't done much wrenching on outboards.

 

[mbullen]

Good to know. Its an old boat and I suspect it was rebuilt one time before I got my hands on it. But I think my build will be pretty close to what it had coming out of the factory.

I will definitely be doing a compression check before even trying to fire it up. Turning it by hand it at least has some compression. Its sitting on its side on a cart in the corner of my garage until I get my Transom back together. As long as compression checks out I will do carb cleaning, fuel pump, fuel filter spark plugs, water pump, lower unit oil. Not sure of anything else I should do on an engine that has been sitting for 14 years. Are there lower unit seals I should consider replacing? I haven't done much wrenching on outboards.

You wouldn't need to do gearcase unless it's leaking. Even then, one can usually just replace it more frequently.
If you find the milky tell-tale in the current gear oil, a pressure test is available to narrow the specific culprit.
Otherwise, you're on the right track. Fuel lines might be suspect - including the tank line, but you've covered all the usual suspects.
The only frustrating part could be a spark issue and the cdi ignition. No real good elimination tricks there except the remove-and-replace game with a fairly expensive ignition module.
Best of luck to you.
I think those are pretty bulletproof motors, personally.

 

[Zum]

Not to much to add but nice looking boat, bet it cleans up nice.
Old 2 strokes are pretty tough, like mentioned a compression check will tell you alot.
For me the only reason to go to a 4 stroke is the noise on long runs and maybe fuel.

 

[thill]

A 60 will push that hull well. If it's a 2-cylinder 60, and it runs well, go with it. Most of the later OMC 60s are 3 cylinder, and are quite strong, but maybe 50 lbs heavier. That is exactly what I put on my boat, and it runs about 40:

 

[rocknroj]

The 'HP Capacity' is based on the boat's construction and the transom's ability to absorb torque and force.
The factory engineers make that call.
Anything in the neighborhood of the max rating is going to be comparable (unless your insurance company objects).

The weight of a motor falls under 'Weight Capacity' and is part of the total weight including motor, fuel, people, and gear.
This is a formula based on displacement.
The balance of is up to you.
Relocating gear and passengers for better planing is trial and error.
If you choose a heavier motor -and since the motor can't be relocated- you'll have less to work with up front.

I have a 17 ft Aluminum side console I am working to restore. Its a pretty lite boat but its rated for 7 people or 1750 lbs (which seems high).

The boat will be used primarily on the Puget sound for Crabbing and salmon fishing. I will also probably take it on some longer trips to the islands and overnight camping and some lakes.

It is rated for up to 65 hp. It came with a early 80s Johnson 60 hp. I am not sure on the condition yet but I plan on getting it running and using it for a while. I would like to eventually switch over to a 4 stroke. I do like the idea of having extra power on hand and do enjoy going fast when conditions permit. I am thinking the 60 will scoot it along quite well.

I know hp ratings can be kind of misleading. In general are all 60 hp engines created equal? Would a well running old 60 hp be comparable to a new 60 hp? How would a modern 50 hp 4 stroke compare to my old 60 hp 2 stroke? I am thinking the minimum I would put on it would be a 40 hp. 50 hp seems like a good middle ground for power and weight. 60 hp would be nice but might be more engine than I really need on this boat.

Any thoughts or advice would be appreciated.

Pics of the boat before restoration

 

[rocknroj]

I do the same mostly area 10..

You may want to find some data on the overall weight of the max rated hp from that era and use it as guide, and of course factor in your kicker weight. The strength of the transom is key and the boat takes a beating when being trailered. I have seen welds break.

The 4 strokes weigh a lot more though some of the newer ones have gotten lighter. At some point hp ratings switched from the powerhead to the prop so a newer 40 hp may equal an older 50 hp.

I run a 50hp merc classic on my 16ft starcraft ss. Not go fast but ok. I don't think my hull is designed to go fast. My kicker is an old honda 10hp and I think the combined weight of the 2 adds up to the weight of what would have been max rated power for the boat in its day.

 

[Whidbeyboater]

I do the same mostly area 10..

You may want to find some data on the overall weight of the max rated hp from that era and use it as guide, and of course factor in your kicker weight. The strength of the transom is key and the boat takes a beating when being trailered. I have seen welds break.

The 4 strokes weigh a lot more though some of the newer ones have gotten lighter. At some point hp ratings switched from the powerhead to the prop so a newer 40 hp may equal an older 50 hp.

I run a 50hp merc classic on my 16ft starcraft ss. Not go fast but ok. I don't think my hull is designed to go fast. My kicker is an old honda 10hp and I think the combined weight of the 2 adds up to the weight of what would have been max rated power for the boat in its day.

Thanks for the info. I didn’t know they switched to the rating at the prop vs the power head. That gives me more confidence that a newer 50 or even a 40 would works okay on this boat.

How much of the engine hp rating on a hull has to do with weight vs the power? I figure if it was weight they would put an engine weight limit since there are a lot of different engines and engine weights to consider. I always assumed it had more to do with the strength of the transom and ability to hold up to the torque the engine is putting on it. It’s probably a combination of both factors.

 

[LaqueRatt]

I'd stick with what you got pal. Old and simple. Give it a quick going over and it'll last longer than you will! New stuff is overly complicated and just like a newer car I figure it'll be less reliable. EG: If it has a computer it'll be a PITA.

 

[Wayne Roberts]

Stick with what you have.........that's what I would do! Get it running well......keep it running well and go enjoy the boat!

 

[thill]

If 1978-1984, a powerpack is only $46.99 on Amazon:

Evinrude-Outboard-CDI-2-Cylinders-1978-1984

Pull the plugs, spray a little WD40 in the cylinders, turn it over a little bit, then check compression and spark. Those engines are tough. Hopefully, it has good compression and spark.

Often, with old motors that have been sitting, the wires and connections are the issues. Look for white or green corrosion in the spark plug wires, the primary wires going to the coils and in other places.

If you have good compression, spray a little starter fluid into each carb and see if she pops. If she does, you are halfway there already.

Carb cleaning, fresh impeller, check the lower unit fluid color and maybe throw in some fresh spark plugs, and you may be on your way to the water.

 

[Whidbeyboater]

If 1978-1984, a powerpack is only $46.99 on Amazon:

Evinrude-Outboard-CDI-2-Cylinders-1978-1984

Pull the plugs, spray a little WD40 in the cylinders, turn it over a little bit, then check compression and spark. Those engines are tough. Hopefully, it has good compression and spark.

Often, with old motors that have been sitting, the wires and connections are the issues. Look for white or green corrosion in the spark plug wires, the primary wires going to the coils and in other places.

If you have good compression, spray a little starter fluid into each carb and see if she pops. If she does, you are halfway there already.

Carb cleaning, fresh impeller, check the lower unit fluid color and maybe throw in some fresh spark plugs, and you may be on your way to the water.

I am very hopeful that this is all it needs. I can feel some compression just turning the flywheel by hand so I know it at least has a chance.

It is pretty clean under the cowl. No corroded connections as far as I can tell. Should have it mounted back up on the boat in a few weeks to test out. Glad to hear these engines have a good reputation. I would prefer old simple and bullet proof over something new and expensive to fix and work on.