Replacing Mariner 60 2st with Yam 50 4st

[cameronke]

Hi folk

I am replacing my 15 year old Mariner 60hp (3cyl 2 stroke) with a couple of year old Yamaha 50 (4 cyl 4 stroke) on my 5.5m Northcraft

The lad that sold me the Yamaha 50 claims it will be almost the same power as the Mariner 60, his reason being that the Yamaha is rated at the prop whereas the Mariner is rated at the power head.

Would you concur?

Certainly the Yam prop is about 1.5 times the size of the Mariner.

Anyone any idea how performance and economy might compare?

Regards
Cameron

[Biggles]

Seeing that you say the Yam 50 prop is 1.5 times the size of your mariner makes me think it could possibly be a High Thrust engine.
If its a High Thrust model then it will be 50 Hp but the output from the prop at WOT will shove you along at less of a speed than a normal engine this is because the gearbox is larger and its geared lower than a normal engine so acceleration is just like a 2 stroke, but the top end suffers.
I could live with mine when I had it.
If I'm wrong I'll shut up.

[Nos4r2]

Originally Posted by cameronke

Hi folk

I am replacing my 15 year old Mariner 60hp (3cyl 2 stroke) with a couple of year old Yamaha 50 (4 cyl 4 stroke) on my 5.5m Northcraft

The lad that sold me the Yamaha 50 claims it will be almost the same power as the Mariner 60, his reason being that the Yamaha is rated at the prop whereas the Mariner is rated at the power head.

Would you concur?

Certainly the Yam prop is about 1.5 times the size of the Mariner.

Anyone any idea how performance and economy might compare?

Regards
Cameron

No. He's talking bollocks.

The ratings changed from powerhead to prop in mid 80's. The 3 cylinder Mariners are prop rated.

Are you interested in selling the Mariner? PM me if you are.

[cameronke]

Many thanks for your comments. The guy I bought engine from is an outboard repairer so I will check if it is the high thrust version

Regards
Cameron

[Downhilldai]

50hp on a 5.5 Northcraft????

Is there a speed limit where you use your boat?

I'm surprised you're even considering that little power on a boat that size/weight. Don't do it.

[matt h]

90 would be good!!