What Is the Right Horse Power ?

[Adelie]

Originally Posted by Ex-Calif

I expect the incremental costs are negligible, the increased full burn when pushed is negligible and as any mechanic will tell you, "There is no replacement for displacement."

Of course the mechanic is going to say that they get paid by the hour.

Larger engine, 5-10% more installation time. 25-50% more time redoing the engine beds, 5-20% more time dealing with assessories in an engine space that is more crowded with a larger engine.

The change from a D1-20 to a D1-30 is going to be an extra $1000 or so from what prices I have been able to find. The mechanic is also going to have an incentive into getting you to upgrade a lot of the ancillary equip to go with the larger engine.

It's starting to look like the incremental costs are not so negligible.

At full throttle on the D1-20 it will be burning about the same fuel as the D1-30 at 2/3 throttle, lets say 0.7 gal/hr. At full throttle the D1-30 is going to burn 1.05 gal/hr, 50% more fuel. In flat water that might get you and extra 1kt.

Increased fuel consumption at full throttle doesn't look very negligible either.

Intelligent decisions regarding compromises can't be make without some understanding of the reals costs involved.

[Ex-Calif]

Originally Posted by Adelie

Larger engine, 5-10% more installation time. 25-50% more time redoing the engine beds, 5-20% more time dealing with assessories in an engine space that is more crowded with a larger engine.

The change from a D1-20 to a D1-30 is going to be an extra $1000 or so from what prices I have been able to find. The mechanic is also going to have an incentive into getting you to upgrade a lot of the ancillary equip to go with the larger engine.

It's starting to look like the incremental costs are not so negligible.

At full throttle on the D1-20 it will be burning about the same fuel as the D1-30 at 2/3 throttle, lets say 0.7 gal/hr. At full throttle the D1-30 is going to burn 1.05 gal/hr, 50% more fuel. In flat water that might get you and extra 1kt.

Increased fuel consumption at full throttle doesn't look very negligible either.

Intelligent decisions regarding compromises can't be make without some understanding of the reals costs involved.

Are those percentages for the installation time a quote you received or an educated guess? He is already switching from one model of engine top another (repower) I would not accept a different quote for a different engine.

Also a quick look at the Volvo product specs shows both motors at around 16 inches wide and with sail drive about 30-31 inches. I didn't get into the mounting and bedding but I bet it's similarly close.

My point about fuel consumption is that in flat water you only need 2/3 throttle to make hull speed, for example. The full throttle is there when you are against chop, wind and tide.

I did not mean to imply there wasn't a fuel burn difference at WOT.

[IdoraKeeper]

Idora was built with northern California and north of that in mind. The boat came new at 26000 lbs displacement with a 65hp Yanmar installed. I have never needed to use it all yet. Fuel flow averages 1 gal/hr.

[Adelie]

Originally Posted by Ex-Calif

Are those percentages for the installation time a quote you received or an educated guess? He is already switching from one model of engine top another (repower) I would not accept a different quote for a different engine.

Also a quick look at the Volvo product specs shows both motors at around 16 inches wide and with sail drive about 30-31 inches. I didn't get into the mounting and bedding but I bet it's similarly close.

My bad, not bright enough to look up engine dimensions on my own and didn't think it all the way thru.

[kene66]

Thank you all. A really helpful thread.