Will a 30hp Tohatsu get this boat on the plane?

[Westcoaster888]

Greetings. I'm a new member who recently bought a 1970s vintage 16-ft Fiberform (faux lapstrake) without an engine. There is baffed-out 50hp Johnson 2-stroke on it now that I am replacing. On my budget, I'd like to go with a new 30 hp Tohatsu, but I'm not sure if this will get the hull to plane. Any more speed that what's required for that doesn't interest me. The manufacturer's tag (Canadian Fibreform Ltd, Kelowna, BC) states the max engine size is 100 hp and max payload is 1,665 lbs. The boat is in great shape, so anyone who has any information that will help me get this beauty in the water will be gratefully received. Thanks.

 

[crabbybait]

probably not.. borderline at best.. i have a 2000 40d2 3 cyl / 3 carb.. mine mite do her.. maybe a new fuel injected mite equal my 40.. good luck with her,, tho..

pretty neet craft ..!! ya just gotta love it..!! it'll have to be fun to play around on..!!. ..

 

[jbcurt00]

Dont forget, using an undersized motor will let you putt around, but even if it'll get you on plane, it'll be near the limit of the throttle. Running a 30 at WOT most of the time could burn more fuel then a larger motor might at half throttle +/-, or less.

Throttle up until on plane, then back off until it'll stay on plane and cruise....

General rule of thumb is 70% of max capacity, so w a 30, you're still not even half of that...

Just to be clear, are you shopping for a new motor specifically, and the 30 is the limit of your budget?

Nothing wrong w that, but even for putting around, I dont think you'll be happy w the 30, or at least not for long...

I used a 5hp on a small fishing boat (rated for a 12hp) because I had it, it ran and it did get me out on the water. But w just 2 in the boat, w out much gear, it was slow and mostly plowed. Burned quite a bit of fuel, and had to be run at nearly WOT to get anywhere.

The 9.5 on it now makes it a completely different boat ride...

If I could have gotten a larger hp motor when I got the boat, I would have. I couldnt at that time.

 

[Sea Rider]

It's all relative. Max 100 HP rated for how many passengers ? passengers and load are key to this equation. Usually break the 70% rule of thumb capacity quite often. If OB sits at the sweet transom/engine height, is well trimmed, deck weight well balanced & boat has a low hull drag coefficient number, a prop maximization will do the trick to get all the horses out of that 30. Just don't expect to run at full passenger capacity which isn't known ?

Don't know about 4 strokes Tohatsu OB's, new 30 HP 2 strokes OB's are being factory delivered with wrong 13 prop pitch which delivers 1K less max wot rpm on light applications, much worst on medium to heavy applications. That OB should have been factory delivered with a standard 11 prop pitch and then go from there maximizing pitches to suit your boating needs.

In your particular case, will need to install an induction Tiny Tach or Hardline tach, go for a wot spin you alone on flat calm water cond and check wot rpm range, then go from there playing with prop pitches to suit your boating needs. Remember, fun comes immediately after fast displacement speeds...

Happy Boating

 

[Westcoaster888]

Thanks Sea Rider, jbcurt00 and crabbybait. From what I'm hearing here, a new 30 hp Tohatsu is not in the cards power-wise and a new 40 hp or 50 hp is a budget-buster for me. The boat is rated for 6 passengers, but I'll only ever carry max 4 people, so that will save a lot of weight. The original engine was a 50 hp Johnson 2-stroke, and the former owner said the boat went like stink with that on it. So I guess my best option is to find a late-model 40 hp or 50 hp 2-stroke, which I know won't be too heavy for the transom and will get the boat up on the plane without running at max revs.

 

[Sea Rider]

Previous owner was probably not that expert tuning that combo, a 50 HP should perform quite well on that boat while medium loaded along ideal tech parameters. I'm currently running a Rib rated for a 50 HP OB and max 7 passenger capacity with just a 18 HP, 3 up and running at 5500 wot rpm which is middle wot rpm range with no issues due to having made a prop maximization as previously described.. Is it possible to test a demo 30 HP OB before buying ?

Happy Boating

 

[jbcurt00]

....18 HP, 3 up and running at 5500 wot rpm which is middle wot rpm range with no issues due to having made ......

I think you have a typo, isnt 5500rpm the MAX for your Tohatsu not the middle lf the range?

It is according to Tohatsu

produces 17.7hp at 5500rpm at WOT

Everything about your RIB is completely different then a big heavy fiberglass 1970s boat

There are lots of motors that fall into a great sized OB for this boat. I'd recommend a 3cyl Johnson/Evinrude triple, which IIRC is available as up to a 75hp.

 

[Sea Rider]

Nobody said 5500 rpm is the max wot range, that's with 3 up at plane.

Max Wot is 5800 rpm

Maximized Prop (8 pitch) from standard delivered 9 pitch

01 up : 6300 rpm (have both eyes on tach if solo boating)
02 up : 5800 rpm
03 up : 5500 rpm

Wot numbers on ideal water cond. Maximizing prop is key for my equation compared to the results obtained previously with a 9 prop pitch. 500 + revs with 1 less pitch.

OP asked if a 30 would plane his combo ? not saying he must buy a 30 HP, if he can test one, much better, specially if having budget issues. In agreement a larger OB would be ideal to go for.

Happy Boating

 

[jbcurt00]

I didnt think the info about RPMs or WOT was clear before, or that it was a typo.

Thanks for clarifying,

 

[Westcoaster888]

Thanks all. There's a 2005 Honda 50 hp 4-stroke for sale locally, as well as a same-spec Yamaha , so I'll go have a look at them. Probably not much heavier than the ancient 50 hp Johnson 2-stroke that was on the boat.

 

[crabbybait]

glad for ya.. that new 30 tohatsu would have an undeserved life of abuse.. now your cookin' ... your gonna love this boat..!!

 

[Sea Rider]

Go for a prop maximization if wanting to get all the horses out of that 50 along having fun with 4 up while boating with a underpowered OB for that application.

Happy Boating