Water bathing and recipes

Hi. I’ve finally bought a water bath pan and am busy trying lots of recipes. I love the recipes in Pam the Jam’s cookbooks but can’t seem to use her timings. In the river cottage handbook She says (for example) to put the jars into the waterbath at 38C and bring to 88C over 25 minutes. Well I’ve tried that and with my electric hobb it took over 1.5 hours to get to that temperature. I don’t know what that’ll do to taste/texture of the preserve but also want to make sure it’s safe, preserving wise.

Is this a common issue? Does anyone have any tips? It’s ok when I can find a similar recipe (the passata one on this site for example) but that’s not always possible. Thanks for any thoughts or suggestions