40HP on 5m fibreglass boat

[seasponge]

Hi Raiders, 

 

I have a 5m Stejcraft Stallion fibreglass boat which currently has an old 70HP four stroke motor on it. I've got a number of issues going on with the motor (overheating, stiff pivot tube, broken tilt/trim toggle on throttle, corrosion on bottom leg). 

I also have another aluminium runabout with a 40HP two stroke Evinrude motor on it. I bought the motor new about 8 yrs ago, it has done very little hours, and I know its full history. The aluminum boat is very old and the size and layout of it does not suit the family boating I want to do. 

With all the issues going on with the 70HP, I am considering whether to put the 40HP two stroke onto the fibreglass boat. The fibreglass boat is the boat I want to be use as it is better suited for the family boating I want to do at the moment.

So, a few questions for all those out there with much more boating experience than myself. 

1. How would a low-hours 40HP two stroke motor go on a 5m fibreglass boat (getting up on the plane, and top speed)? I don't do any offshore boating, all estuary based in the Hawkesbury. 

2. How do I know the weight of my boat - Stejcraft Stallion `5m, not sure of the year.

 

 

[frankS]

Well to be quiet blunt It will be sluggish, it will push the boat along but probable only at displacement speed, that is not on plane. in good conditions and with the tide it may get up on the plane with a bit of a push and once on plane it could go along comfortably.

With the family on board it will be a slug.

What I would be doing if I were in your position is have a look around for another 40hp and put it on side by side so you would have twin 40's and that would make the boat a ripper.

Control box might be a bit awkward to get used to but you would soon work things out.

Think the transom is wide enough for twins.

Frank

PS photo of rear (transom) would be nice.

Edited September 9 by frankS

[noelm]

The old motor is not worth spending some cash on? That is a Suzuki motor, and those ones dud have an issue with a steel plug in the bottom of the motor, but they were a good motor.

edit…..a 40 on that boat will be a slow old trip, it will go, but chances are planing will be out of the question, you might be able to find a prop small enough to make it useable?

Edited September 9 by noelm

[XD351]

If they were my boats I would sell the runabout with the 40 as it is - you should get decent coin for it . Use the money to fix the 70 , some of the issues may be a straight forward fix - overheating can be a stuck thermostat , a weak pump or it could be more serious, you need to get that checked first . The tilt trim toggle and a bit of corrosion are not things I would panic about , possibly get a new controller either OME or aftermarket- what about second hand? The pivot tube isn’t something I have ever had issues with but surely it would be stainless? Might need a grease job or a rebuild ? 
also need to remember that switching motors over will cost you some money - not sure if the control cables for the 70 will fit the 40 and if not are the cables for the 40 long enough for the stejcraft? 
just my two bobs worth ! 

 

[Bryant fish]

I have a slightly smaller boat that has twin 40s if i have ever had to come back on one motor it is ridiculously slow dont do it what frank said is right if you can find a identical motor and it fits a twin setup is good 

[Bryant fish]

Also you have to make sure the length of motor suits the boat 

[seasponge]

4 hours ago, frankS said:

Well to be quiet blunt It will be sluggish, it will push the boat along but probable only at displacement speed, that is not on plane. in good conditions and with the tide it may get up on the plane with a bit of a push and once on plane it could go along comfortably.

With the family on board it will be a slug.

 

3 hours ago, noelm said:

.a 40 on that boat will be a slow old trip, it will go, but chances are planing will be out of the question, you might be able to find a prop small enough to make it useable?

 

55 minutes ago, XD351 said:

also need to remember that switching motors over will cost you some money - not sure if the control cables for the 70 will fit the 40 and if not are the cables for the 40 long enough for the stejcraft? 

 

Thanks all for your replies. Probably what I suspected. 

I fear the seized pivot tube is going to be a major headache. Has anyone had any past experience with pivot tube issues in the past?

[Bryant fish]

Check its not the cable

[seasponge]

21 minutes ago, Bryant fish said:

Check its not the cable

Yeah I've done that. Disconnected the steering arm, cable moves freely. Can't budge the motor by hand.

[noelm]

Depending on what steering part you mean, the pipe with the thread on each end that the cable goes through is the tilt tube, it’s easy enough to replace. The big section the entire motor turns on is the swivel bracket, it’s a crap job to fix, not difficult, but dirty and messy, an engine hoist to support the motor will make it relatively easy, done a few of them over the years, the trouble starts when the wrong grease is used.

[noelm]

You can buy a bit of time by heating the steering with oxy (without setting fire to the boat/motor) and pumping proper marine grease in there, but it will seize up again, the only fix is pulling it to bits, cleaning all the dried up “stuff” out and replacing the nylon bushes (if it has them) you will find grease will only come out the bottom, the top will be caked up hard.

Edited September 9 by noelm

[seasponge]

I guess I'm referring to what you called the swivel bracket. I've only seen it referred to as the pivot tube. And its definitely beyond my level of capabilities, equipment or available time. Think I'll just have to get it down to the mech and see what they have to say. 

[dunc333]

your better off going to see the mechanic and seeing whats available in the 70 to 90hp range new or second hand and trade or sell the other 2 donks cheers dunc333

[JonD]

I Europe 40-50hp would be a common power range on a 5m boat but not so much here. Obviously you would need to reduce the prop pitch to get the motor running out to its max rpm range. Top end speed won't be amazing but I still think you may be able to get 20-22kts out of it at full rpm and propped right. Economy won't be great as you will be running it in the high rpm range. Hull shape and weight will obviously effect how well it runs but in my option with the right prop it could be done.