40hp Mariners 1985 twin carb Vs 1998 single

Commando C2 · 08 May 2011, 17:25

i have just picked up these motors, tiller steer short shaft both ex rnli. (lifeboats)

Just wondering which outboard will be best to keep, the old one is a yamaha based motor and been well looked after and serviced, the 1998 has stood for a while and the tilt has seized so looking to get that undone asap. both run and engage gears.
the 1985 has been repsrayed so looks tidying from a distance and the 98 has a very scratched up hood, so need to replace it really, but the rest is ok.

Which one will be more fuel efficient and will there be a noticable difference between them (assuming they are both fully working to potential, compression test to follow)

Any experiences of either motor appreciated.
i think the 1985 40hp mariner is about 65kg (143lbs) and the 98 is heavier at 75 kg, and as i willbe moving it and mounting it on the boat on my own i am taken toward the lighter engine although the 98 has gas tilt assist!!! nice.

thanks

PS. cant find the serial no on the 1998 motor (its the later type so guessin circa 1998 and previous owner said it was?!)
where should it be located and can i find out the year from some of the numbers on the engine block??

uncle al · 08 May 2011, 21:12

go for the later obm ,a good obm and the spares will be easyer to obtain, personally i like both but i would go for the late obm ,is there anything stensilled on the legs of the obms if so what?
regards
alan

Commando C2 · 08 May 2011, 21:41

thanks for the advice i did wonder on the availability of parts on the older outboard but have found a dealer that can get all the parts esp as its a yamaha.
i was going to keep the one thats more efficient and with best compression.

nothing stenciled on the legs, the 1985 had a respray but has the exhaust guard on the back which is an rnli add on.
nothing on the 1998 though.

Having trouble unseizing the outboard tilt. Have got one side free and moving after taking off the gas assist. any advice on the best way to free this?

have sprayed with penetrating oil and leaving over night.

Rib T · 08 May 2011, 21:51

I have the twin carb model on the back of my sr4. Reliable and really economical 4 hrs cruising at 21 Knts still had petrol in a 30 litre tank

Commando C2 · 09 May 2011, 20:58

thanks for the info.
i am favouring the 1985 engine as its 65kg and the newer one is 75kg, which is just too much to move around.

Also the newer one as a much larger transom bracket and wont fit on my zapcat, so i am going to keep the twin carb i think.

Will 2 carbs be smoother running than a single or more torque as i think they both have the same 649cc displacement?!