P21 Design max speed

[Peterjfinch]

Hi All, was there a maximum design speed for a 1986 P21?

Pete

[Burty]

dunno about max but a few have been over 90mph with no issues and some used to run twins so i can't see 100mph being an issue as long as you got the right kit

[Cookee]

Originally Posted by Peterjfinch

Hi All, was there a maximum design speed for a 1986 P21?

Pete

I'm not a marine architect, but AFAIK planing hulls aren't the same as displacement boats in terms of max hull speed - more power = faster. For instance put twin 350 Verado's on the back of a P21 and ignoring the fact that it may be a little stern heavy, with 700hp it would go very quickly indeed - possibly into triple digits.

The real question is what's your point?

[Peterjfinch]

Sorry, maybe I should have been clearer. I am using a new insurance company out here (Spain) and the policy says "Max speed (knotts) 20". I called the company and explained that this was probably a little wrong. They asked what the speed of the boat was and, without wanting to inflate the premium too much, I replied that I have only taken it to 40 Knotts but I don't know the exact speed

Their reply was, so what is the boats design speed.

So I thought that I should check, before I give them an answer. I don't want to raise the premium too high but also, don't want to end up without insurance, if they can show otherwise.

Hope this helps

Pete

[hunton69]

Originally Posted by Cookee

I'm not a marine architect, but AFAIK planing hulls aren't the same as displacement boats in terms of max hull speed - more power = faster. For instance put twin 350 Verado's on the back of a P21 and ignoring the fact that it may be a little stern heavy, with 700hp it would go very quickly indeed - possibly into triple digits.

The real question is what's your point?

A little stern heavy

[Tony Davis]

Originally Posted by Peterjfinch

Hi All, was there a maximum design speed for a 1986 P21?

Pete

I think it was supposed to be a couple of mile an hour more than a Ring 21, but I believe that it has never been achieved!

[still no worries]

p21 twin 2.5 ef'is must top 100mph.

[Jono]

Originally Posted by Peterjfinch

So I thought that I should check, before I give them an answer. I don't want to raise the premium too high but also, don't want to end up without insurance, if they can show otherwise.

Hope this helps

Pete

Just tell 'em what your rig will top out at...then you know that you are properly insured......try and "con them" to get a reduced premium will mean you aren't properly insured...and if it goes tits up big time...they will investigate...and be sure they will have access to someone qualified to make an educated guess at your boats performance..then you will be in a world of pain...

[Captain Chaos]

Originally Posted by Tony Davis

I think it was supposed to be a couple of mile an hour more than a Ring 21, but I believe that it has never been achieved!

red rags & bulls spring to mind

[motorvator]

Originally Posted by Burty

dunno about max but a few have been over 90mph with no issues and some used to run twins so i can't see 100mph being an issue as long as you got the right kit

This used to go through ninety so a ton should be easy with todays engines.

[Martin Purnell]

The company that make them now advertise on this site. They must be CE rated with a max power and they may have built one with it.

[andymac]

the ce rating is (i think) up to 300hp but max speed who knows? hutchies ex record(p20) might give a clue,look it up.its kin quick !!

[Wayne Kerr]

Do just as Jono says mate.
If you run the P21 with a 23", tell them so.
If you run it with a 26" tell them you had the accident with a 19".

Insurance company's don't like anything above 50 knots. (IMHO)!

[Peterjfinch]

Thanks for all the answers, this is a bigger question than I thought. I have GPS showing 64mph, without any mods to a standard 200HP Mariner. This is enough for what I want but, as you have said, this is still over the 50 knot.

It sounds like I might be better off de-tuning it and get a survey done. At least I can then quote their speed rating (under 50 knot).

Pete

[Wayne Kerr]

If you have to have a survey done, use a 19" prop.
You'll rev the nuts off the Marina but you can impose a save rev limit of 5000 - 5600 rpm. I think that's what the handbook recomends.

Who's doing the survey?

[Peterjfinch]

Changing the prop makes sense. There is a rev limiter now so how would I reduce the max revs?

Not chosen who to survey her yet but it might be worth it and insure her full comp from now on. Had no problems in the past few years (except a nasty hook, nothing to do with insurance though), So might be the way forward.

Thanks

Pete

[Wayne Kerr]

The way to limit the revs without tinkering is with your right foot (or hand, depending on your set-up).
If questions are asked, just tell them what the book says.
I doubt you'll get anyone on your island (let alone Spain) that knows anything about Phantoms ,,,,, except maybe around the Gib area.