The motor is a 2020 the prop is a 3 blade folding on 130s saildrive
That is a non standard combination and you may need to revisit your 3 bladed folder prop. The 2020 was normally fitted with the 120 drive which has a reduction of 2.47:1. The engine is rated at 3600rpm which gives a shaft speed of 1457rpm. The D1 engines are rated at 3200rpm and the 130 drive was given a a reduction ratio of 2.19 to keep the shaft speed the same at 1461rpm so the same propeller sizes would suit. Your boat was built during the changeover period when the drive change came in before the engine change so will have been fitted with a non standard fixed propeller as with the later drive it has a shaft speed of 1658rpm so needs either a smaller diameter or flatter pitch. Your folding propeller may be to "large" which might explain why you only get 6 knots. Suggest that you do a series of runs in flat water at 200 rpm intervals from 2000rpm up to the maximum. If the prop is right then you should get around 5.5 knots at 2400rpm and 7 knots at between 3400 and 3600rpm.
Just to emphasise the difference the reduction ratio makes, a fixed 3 blade prop for a 2020/120drive would probably be a 14*9 and a 2020/130 a 14*7. The factory fit would probably have been a 2 blade 15*7. These are only indications particularly for the folding props as they have different blade areas and shapes so are often different from fixed props.
The key message is that you need to use every bit of hp the engine can produce as for hull speed (7.2 knots) needs just over 21hp. So if your prop is restricting revs you are not accessing the maximum hp and will struggle in adverse conditions. Of course increasing power by 50% will enable you to easily exceed hull speed and reduce rpm at cruising speed but it is big expense when the boat is not massively underpowered.
First thing is to check that you definitely have a 130 drive - split anodes is the major indicator then run the speed/rpm test and revisit the propeller if you are not getting the sorts of revs and speeds indicated above.
I went through exactly this process when I replaced the 120 with a 130 on the 2030 in my 2001 B37. In that case we fitted a 16*11 2 blade folder instead of the 16*12 fixed.
BTW I have had both a 2030 and a D1 30 both from new and on balance I have a preference for the older engine, although there is nothing really negative about the D1 and it does have some nice features like the bigger alternator. I found it a little less refined in my newer B33
Hope this helps.
