Overpowering a small rib?

[dothedr3w]

Hey everyone,

New to the forum. I'm looking to purchase a small aluminum rib (480cm/15'9") and the max HP rating is 85. Obviously to stay under the max, you'd have to put a 60hp on, but 90hp makes sense to me without being overkill.

Now here's my question, assuming engine weight between 90/115 is the same, would putting a 115hp outboard be overkill? It's only 30hp over max, but it is a small boat, so obviously it's going to make more of a difference, I just think it'd be fun to have a zippy little unit on those clear/flat days.

 

[tinboatrobb]

All boats have a max HP rating. Going over that is not a bright idea and is also illegal. On the water cops check that stuff.

 

[chris73]

Do want a boat or a rocket?

 

[dothedr3w]

Do want a boat or a rocket?

A floating rocket

 

[Dogbreath]

Make the wrong type of mistake and she'll flip.

 

[dothedr3w]

Make the wrong type of mistake and she'll flip.

How do you mean? Like burping the throttle too much in a turn or something?

 

[Brando]

60 on a 15’ rib is lots.

 

[dothedr3w]

Looks like the consensus is that I'm out to lunch. If a 60 is already lots, would a 75 be more reasonable?

 

[Capt_Ed]

I had a 50 2stroke Merc on the 15' Rib i had and believe me it was PLENTY

 

[Pineapple Express]

What specific brand/model RHIB are you looking at? Is it truly a light-weight hull, or is it fitted with a console/T-top/anchor locker and all that stuff?

Without knowing the answer to the questions I've just written here, I'll start out by saying that I'd put a 90hp on it. The 90hp market is pretty competitive with all the major brands having motors with very similar weights.

Also think about what motor to get in terms of nearby dealers for warranty support and parts availability.

 

[dothedr3w]

- 705lbs dry boat weight;
- 120lbs with full fuel (80L);
- 400lbs for motor weight plus rigging;
- 60lbs safety equipment/anchor;
- 200lb operator;

- 1485lbs minimum operating weight.

-480 (15'9") length, 208 (6'10") beam, 22 deadrise, 8 passenger capacity

With a 75hp it's 19.8lbs/1hp.

 

[seabeyond]

- 705lbs dry boat weight;
- 120lbs with full fuel (80L);
- 400lbs for motor weight plus rigging;
- 60lbs safety equipment/anchor;
- 200lb operator;

- 1485lbs minimum operating weight.

-480 (15'9") length, 208 (6'10") beam, 22 deadrise, 8 passenger capacity

With a 75hp it's 19.8lbs/1hp.

You can get a 75 merc that's the same engine as the 90/115. That would be a torque monster but I don't see the advantage on such a light little boat. You won't use it and it's considerably heavier than your smaller options.
I currently own merc/ suzuki/ and yam so I don't really have a brand allegiance. In the sub 90 category, and pushing a light boat I'd go yam/ zuk. This looks like the ideal case for a 70 yamaha.

 

[zurk]

on my 15 foot aluminum which i sold, 50HP was overkill. i would get a 30-40HP max and go with that.

 

[Pineapple Express]

- 705lbs dry boat weight;
- 120lbs with full fuel (80L);
- 400lbs for motor weight plus rigging;
- 60lbs safety equipment/anchor;
- 200lb operator;

- 1485lbs minimum operating weight.

-480 (15'9") length, 208 (6'10") beam, 22 deadrise, 8 passenger capacity

With a 75hp it's 19.8lbs/1hp.

I'm still very curious...what brand/model is it that you're considering? Also, what is your usage? Are you shuttling groups of people around a protected inlet? Are you trying to circumnavigate Vancouver Island with camping gear?


My family has a Novurania DL430 (14ft length, 6ft beam, dry weight listed at 880lbs, which should include the built-in fuel tank) We have a Yamaha F70 (max rated power is 70hp) and it is very fast. The boat has a sharp hull entry and it is VERY sensitive to fore-aft weight distribution and engine trim.

I'm still of the opinion that a 90hp would be the biggest engine I'd put on your mystery RHIB, but I suspect that Yamaha F70 or Suzuki DF60AV would be a better overall match

 

[Tips Up]

For safety, insurance and resale... Stay under the max HP.

 

[Pineapple Express]

You can get a 75 merc that's the same engine as the 90/115. That would be a torque monster but I don't see the advantage on such a light little boat. You won't use it and it's considerably heavier than your smaller options.
I currently own merc/ suzuki/ and yam so I don't really have a brand allegiance. In the sub 90 category, and pushing a light boat I'd go yam/ zuk. This looks like the ideal case for a 70 yamaha.

Seems that the major manufactures are all doing the same: shared engines offered at 75/90/115 ratings done by Yamaha and Mercury. Honda has 75/90/100. Suzuki has 75/90, and their 115 is different.

To stay lighter, the Yamaha F70 is a very good option since it's light and has a large propeller. Suzuki just released a similar motor in the DF60AV (note the V, that's the critical difference).

 

[Fixit]

I ran a 20' Wellcraft (max hp 260) with a 300hp merc 350 mag. I didn't die, insurance didn't care, neither did fish cops. or anyone else.

but without knowing anything about your rhib nobody can say. is it a cheaply built boat, or a hurricane zodiac?. at the end of the day its your boat, your a$$ and your responsibility. Likely a 90hp would be great and fast. but if a well priced 115hp fell in my lap I wouldn't be too worried about bolting it on especially seeing at its the same weight engine. you are the one with your hand on the throttle, enjoy accordingly

 

[chille51]

Pretty sure the rating is more about the power being applied to the transom, than the weight of the outboard. If someone invented a miracle outboard that produced 350hp with the weight/size of a 70hp, it still wouldn't be safe to bolt it to a boat rated for 70hp max.

 

[uclueletcharters]

Inflatables are super stable how they handle is so different than a conventional hull with out tubes. Years ago family had a 12.5 with a 40 yami on it. Handled no problem. Right now I have a small inflatable soft bottom with a newer 3 cylinder four stroke 25hp. Nice part of having the extra jamb is you can line people around the pontoons and it can still get up on step. Depending on what you’re doing with it would be a deciding factor. Pulling people doing water sports behind be nice to have the extra hp. They have a crazy high weight capacity so if you take out lots of people to be able to jump up quick then roll back the throttle to half and cruise is nice. The added weight you probably wouldn’t even notice do to the buoyancy of the pontoons that extends past the transom. They are there own boat for sure. With a 90/115 probably be around a 40mph wot boat.

 

[zurk]

its not an inflatable - its a RIB. that basically an aluminum boat with side tubes.
SIBs have more drag and behave differently than RIBs.