Boiler/Tankless Water Heater Problems - Better to get a tank?

We are the second owners of a 9-year old house with an oil burner furnace and baseboard heating. There is no water heater tank and the hot water is heated by the oil burner furnace.

In 2007, we had to replace the power vent blower motor, which cost us over $900 with labor. The repairman said that the motor probably wore out faster than normal because of the fact that it was running so frequently and year round, every time water was heated. He suggested that we might want to consider switching to a tanked water heater since he could not guarantee how long the new motor would last.

This year, the transformer on the furnace needed to be replaced, which cost a few hundred more. In addition, we have found that the water does not get hot enough in the winter if more than one of the three heat zones in the house is heating at the same time. We were leaning to live with this inconvenience (I assume our tankless water heater is undersized…???), but now, in the past few months, the temperature of the hot water suddenly does not get very warm ever, and it is not even winter yet. I am afraid that there is something new now wrong.

Having now spent over $1,000 on the boiler in the past few years, and being wary of the power vent blower motor going again in the next few years, and now with the new problems with the hot water, I am seriously wondering if it does make sense to switch to a tanked water heater to reduce the wear on the boiler parts.

I know that tankless water heaters are more efficient overall, but I am afraid that in our case, it is becoming a major money pit. As I am previously unfamiliar with tankless water heaters, I am looking for other opinions or suggestions before making a decision though.

Thanks!

ok 1st power venter cause more problems than they are worth if there is any possible way to use a real chimney please do, 2nd the transformers go at about the 10 year mark (lot of times less) it sucks but that is how it is, also i wouldnt worry about the power venter motor quiting for quite some time, 3rd if your having issues with hot water from the coil in the boiler there is 2 reasons for this either the mix valve(if there is one) is failing just have to replace... or the coil has too much mineral build up in it, the best way to fix in this case is to abandon it and go with a indirect fired water heater (aka super store or the like) they get piped into the heating system as their own zone and you have alot more water storage than a coil, i would check the aquastat settings make sure they are running at least 160 low limit 180 high limit (there has to be a 20 degree differential for it to work properly no matter what the setting is).... the good thing about keeping the boiler running all year round is it keeps the boiler from condensing in the flue passages causing sulfuric acid that eats the cast iron and the seals warm and in good shape not leaking, as a rule we have found is if you shut down a boiler it will cut 10 years off its life expectancy

hope this helps