2-stroke vs 4-stroke

[Toerag]

Ken - useful comparison for you - I run an MI21 with a 150hp volvo turbodiesel (AD31P) and reckon on a mile/litre average. A chap on my pontoon has the same hull, but with a honda 135 4-stroke, and he reckons on getting a mile/litre too. We both get the same top speed, no idea about acceleration. Although he has less power, his engine is significantly lighter than mine, and the MI is sensitive to weight in the stern so his boat is the equal of mine. I guess it boils down to other factors - maintenance costs, deckspace, and initial cost. The Honda is lots cheaper than the equivalent diesel, and probably just as reliable.

Personally - If I bought a new MI I'd put one of the volvo D3's in it - they're ~100kg lighter than my AD31 and come in 160 & 190hp flavours. They're also common rail and 5 cylinder, so much quieter than mine.

[ColinW]

I had several Seagull outboard engines and did not suffer the oiling up problem, used to go from Poole Harbour out into Bournemouth Bay and fish all day moving quite a lot whilst drifting for plaice over the Durly Rocks.

 

Standard procedure on end of day was to run engine in 45 gal. drum of clean water, remove spark plug and clean ready for next outing.

 

Had a Seagull 40, Century and Century Plus long shaft all performed very well.

 

Using them like that there is no problem. The oiling only seems to happen when you are trolling for hours on end at idle speed. I think the engine just doesn't run hot enough and the oil condenses out. It's obviously something that could be designed out (and may well be by now) because on the two cylinder Johnson it was only ever the lower cylinder that was affected so at least I could get to the bank on one cylinder to do the plug change. I've got no sea-legs so all my boating was on lochs and lakes!

I've used Seagulls on rental boats and found them far more reliable than the budget far eastern alternatives.

[WALCOTT]

Like NEWT said we must be coming up for Emmission issues re the outboard..they may be here now???and he said his country is on it now...as for the Norfolk Broads where I live must engines which are been or tried to sell are 4 Stroke...may be its because of the wildlife,I don't know,..but I think the 4stroke is winning from what I see on the rivers....the old boys will still use there 30yr old plus Seagull to go netting etc..another thing with new/modern outboards is getting the right prop for the craft..moving ballast about etc to get it to plane,try another prop etc..I still cant think what them Diesel outboards was called...but they looked the biz at biz money aswell....its up to each of use what you want in the end.

[Sharkbyte]

Hi Walcott

 

Are you referring to the Yanmar (27+36hp) diesel outboards. Seriously pricey as I seem to remember.

[Toerag]

Hi Walcott

 

Are you referring to the Yanmar (27+36hp) diesel outboards. Seriously pricey as I seem to remember.

 

The Alderney water taxi has one of the 27hp jobs on it.

[WALCOTT]

I can't remember what make but I know there was some noughts on the price...but you don't here owt of them now,but I a sure they are still about.

[doshkadog]

The MOD are adopting a policy of INTEROPERABILITY which means everything should run on the same fuel as a result there will be more diesel outboards being built for the Navy.

[Ian Burrett]

My pal has just bought two secondhand yanmar 36's from a port authority.

 

They cost £18,000 new but burn only 3 litres per hour. I don't know what they weigh but they look huge

[chesters1]

my old boss had his 2 caterpiller engines taken out of his boat and real ones put in

[groyne bandit]

Probably not the answer your looking for , but i fish on a headland ,,,when the boats go out past me with a 2 stroke all i can smell is neat fuel ,,,it stinks for yonks ,the bloke i admire most comes past in a 15ft with a little diesil motor banging away ,,ok he takes 1 hour as oposed to 20 mins ,, but what goes through my mind is he has just done the same trip ,,on 5ltrs of diesil , and he has got a better tan ,,,,,,

Edited June 30, 2007 by groyne bandit