10hp 4 stroke versus 15hp 2 stroke

[rigpigpaul]

Hi All, I now have a 3m rib dinghy and I need an engine. I am looking at a 10hp 4 stroke or a 15hp 2 stroke. I believe they are similar in weight. I will only be using the dinghy occaisionally so fuel consumption is not high on my list. I do want to get onto the plane with two people and bags of shopping. Quiet as possible and maybe an electric start would be nice. The engine will have a tiller arm.
All tips will of course be appreciated. What would you buy, if you knew then, what you know now!
RPP

 

[NornaBiron]

We have a 10hp 2 stroke with our 3.1m rib. It will plane with two of us but not with the month's shopping too. It's heavy, we manage it by hoisting with one of the dinghy davits, and it's thirsty. We love it though, it's great for exploring. We also have a 2.2hp 2 stroke which we prefer for every day use. It is easy to handle, sips petrol and gets us ashore safely in most conditions that we'll leave the boat in, if a bit slower than the 10.

The 10 is the same weight as the 6hp 4 stroke that we use to have so I suspect that a 15hp 4 stroke will be quite a bit heavier than the 10.

 

[TQA]

I have a Tohatsu 18 hp 2st. Planes 2 up with shopping with ease. It is also economical.

N.B. Where I am the 18 hp is a couple of hundred dollars cheaper and weighs the same.

4st engines are quieter.

 

[geem]

We have a 2.9m rib with tohatsu 9.8hp. the engine weighs 26kg. This set up planes with two of us and a little shopping. The engine is very economic to run. On a three week holiday we used no more fuel than a pal with a 3.5hp on a dinghy with four people on board. We did a lot more distance in our rib as well. the twin cylinder 2 stroke 9.8hp is easier to start than our single cylinder 3.5hp engine as you don't need to pull it so hard.

 

[rivonia]

When we were in the carribean we had a 3m RIB with a 10hp 2stroke it planed with two people and some shopping. In the Med we had a Rib the same BUT had a 4 hp mercurey 4 stroke... Disaster. It was just too heavy for us to lift. It did plane though with two peolple just. Go for a two stroke every time.

 

[david_bagshaw]

We have a 3.2 mtr rib with 8 hp 4 stroke, planes easily with 2 + shopping, however we fitted fins to the cavitation plate to improve its planing performance, back to that before fuels in europe were reduced to the lead free low ron standard.

 

[Hadenough]

We have a 2.9m rib with tohatsu 9.8hp. the engine weighs 26kg.

Are you sure? Mine weighs 41kgs and don't I know it!

 

[GSL]

Go with the two stroke every time.

They use more fuel, but in reality how much do you use, so much lighter to lift on or off and soooooo much easier for a woman to start.

I have had a 10HP Mercury on an Avon 3.2 RIB, struggled to get going with more than two people on it, I even bought a set of Lifting Fins for it from USA, still not what I wanted. Still have the Lifting Fins / Tabs if anyone wants to buy a set.

Changed to a 15HP Mariner two stroke, brilliant. So much power to spare, half throttle got you everywhere on the plane. So much easier to start also.

I now have a 2.8 meter Walker Bay with a 13.5 HP Yamaha 2 Stroke, great engine.

Would never go back to a four stroke on a RIB. The weight alone makes it a no brainer to me.

Graham

 

[NornaBiron]

Are you sure? Mine weighs 41kgs and don't I know it!

Our 10hp 2 stroke weighs in at 28kgs

 

[geem]

Are you sure? Mine weighs 41kgs and don't I know it!

Absolutely sure. Two stroke. Check the net. 26kg. It's the reason a bought it. Had it since 2005. Been a great engine

 

[charles_reed]

Definitely the 2 stroke - if you can buy it legally - it's lighter, will certainly plane your RIB and will probably be more reliable.

 

[GSL]

Definitely the 2 stroke - if you can buy it legally - it's lighter, will certainly plane your RIB and will probably be more reliable.

Hi Charles

I am not disputing your comment, but I would like to hear clarification as to why you feel the two stroke is possibly more reliable.

I have always felt that the two stroke can suffer slight fuel feed problems from "gumming up" the carb when or if fuel is left too long in the float chamber.

Would appreciate any experience you may have had regarding four stroke reliability. No question in my mind, two stroke every time.

Graham

 

[rivonia]

Hi Charles

I am not disputing your comment, but I would like to hear clarification as to why you feel the two stroke is possibly more reliable.

I have always felt that the two stroke can suffer slight fuel feed problems from "gumming up" the carb when or if fuel is left too long in the float chamber.

Would appreciate any experience you may have had regarding four stroke reliability. No question in my mind, two stroke ebery time.

Graham

You will find that if you leave petrol in the FOUR STROKE and do not use over winter...It also gums up!!

 

[GrahamM376]

Hi Charles

I am not disputing your comment, but I would like to hear clarification as to why you feel the two stroke is possibly more reliable.

I have always felt that the two stroke can suffer slight fuel feed problems from "gumming up" the carb when or if fuel is left too long in the float chamber.

Would appreciate any experience you may have had regarding four stroke reliability. No question in my mind, two stroke every time.

Graham

I agree with Charles. From personal experience I have found 2 strokes to be more reliable and have never suffered from fuel gumming up. Mechanically, there are more potential problems with a 4 stroke which, unlike 2 strokes have a camshaft, valves and tappets to adjust.

 

[charles_reed]

Hi Charles

I am not disputing your comment, but I would like to hear clarification as to why you feel the two stroke is possibly more reliable.

I have always felt that the two stroke can suffer slight fuel feed problems from "gumming up" the carb when or if fuel is left too long in the float chamber.

Would appreciate any experience you may have had regarding four stroke reliability. No question in my mind, two stroke every time.

Graham

Basically because it's got fewer moving parts - with modern ignition systems the main disadvantage of 2 strokes appears to have been overcome.
Certainly you can get an oiled-up carburettor but the solution is simple, always run the engine to a stop by turning off the fuel.

 

[GrahamM376]

You will find that if you leave petrol in the FOUR STROKE and do not use over winter...It also gums up!!

I think the gumming up issue is overstated and could mainly be with older machinery with more oil in the fuel. Yes ir does sometimes happen but, if it were the norm, very few people wold be able to start their lawnmowers in the spring. I dug my petrol driven power washer out this morning, added some new petrol to the old and it started after a few pulls, having been unused for around 12 months. Never had problems with 2 stroke outboards gumming up during 16 years use.

 

[pyrojames]

I have a 15hp Mariner (Yamaha build) on a 310 RIB. Great combination, planes easily 4 up, fast to run in from outer anchorages. Too heavy to lift so need to use a halyard to get it aboard. Can just struggle to carry it when needed and get in/out of the car. Old reliable and was cheap from ebay, along with RIB and trailer...