Underpowered mac 19?

[magnetic]

Hi - just took my recently-acquired Mac 19 out for the fist time and have to confess to a degree of disappointment about the performance when under power.

The boat has a very well maintained Yamaha 25hp 2-stroke, but won't get up on the plane or go past 7mph according to the GPS; direction relative to the wind makes no difference, the boat is not heavily loaded and the props seems fine.

OK - I could of course fit a 200hp lump and be done with it, but I hope I don't have to do that; I could get the engine serviced, re-tuned and perhaps re-propped, and I probably will do all of those. The purpose of this question, however, is much simpler -

"How fast SHOULD a Mac 19 go with a 25hp outboard?" - if the answer is that this power will never be sufficient to push the boat up onto the plane, then all of the props and servicing and DoleFins in the world arent going to help!

One final question, if I may - where does the sink drain to - is it straight into the bilges?

many thanks in anticipation of your kind responses

Andrew

[Duane Dunn, Allegro]

The Mac 19 was designed to use a 40hp engine. Most find it to be quite a good powerboat with 40 hp. Of course most motor manufacturers 40hp and 50 hp share the same power head so for the same weight you could use a 50 hp. As the Mac 19's haven't been made since 1995 you are way past any warranty concerns about using the 50 hp motor.

Look around outside and I'm sure you'll find a drain through hull somewhere for the sink. MacGregor moulds them in rather than using the more traditional style through hulls.

[magnetic]

Silly me" I should have made it more explicit - please accept my apologies for not explaining my situation - I have only just got the boat and before piling in with another £2,600 / US$5,000 to buy a shiny new Tohatsu 40hp, I wanted to make sure that this really was necessary - if the 25hp is too gutless, then it's 40hp or nothing.

IF, on the other hand, 25hp is just fine for, say 13kts, then I would appear to have a fuel/carb/tuning/prop issue with the existing engine - which is probaly a tenth of the cost to fix.

Just trying to save money, you see

So then, if any of you could please help me with my original question - how fast SHOULD a 19 go with a properly set-up 25hp? I know it will go a lot faster with a bigger engine. However, right now I am focusing on the one that it has already got!

many thanks

Andrew

[NiceAft]

Andrew,

I believe the man you need to speak to is Highlander.

Offer to get him a bottle of Monkey Shoulder Scotch and I'm sure he will offer his advice.

Try giving him a private message.


Ray

[beene]

Hi

I think Alex has a smaller motor also.

He has a and a 30 I believe.

He recently re-propped and his speed at WOT was much better with a lower pitch.

What are your rpm's at WOT.

G

[magnetic]

Hi - many thanks for the responses to my query; I have a Tiny Tach and will wire it up next weekend to see what the revs are currently at. I assume that too low revs (<4500 for this type of engine) would mean that it's either overpropped or not running correctly? If, on the other hand, it's cracking up to 4,500 - 5,500, then presumably I'm stuffed.

It is slowly dawning on me that if I were to put a 500 hp V8 hotrod engine on the back, or if I sorted the current engine and prop out, then performance might perhaps be slightly different.

However, my question is really much, much simpler -

IF the current 25hp engine was running just fine AND the prop was right, would it still be incapable of pushing the boat up on the plane?

Alex, Highlander, Jim - any guidance would be really welcome, as the cheapest new Tohatsu I can find is well over £2,500 and if I can avoid paying that, then the whisky would certainly follow

[Frank C]

It seems you're feeling just a bit of frustration from a lack of answers to your specific query
. . . . . . . WOT speed for a Mac 19 with a 25 hp outboard

Please understand that, though this membership numbers 2,000, there are probably fewer than 500 who are visiting frequently. There are probably fewer than two dozen current/former owners of the Mac 19. Further, since the factory standard was a 40 hp, YOU might be the only one (visitor here) with experience of a Mac 19 with an outboard at 25hp.

Hoping to find a similar power setup might be a bit optimistic. Hoping that the comparative hull loading and motor that are similar-enough ... maybe wildly optimistic. Another person (if he exists) with experience to answer you ... might visit here only every 2nd week, or so. I hope you find a specific answer to your query, but you might not.

As for the expense of fitting a larger outboard, it could easily be done here in the USA. There are numerous owners of the 26-footers with Honda 50, or EFI Suzuki 50 who would love to sell their low-hours motors for upgrading to the 70 or 90 hp range. I'd think a low-hours 50 is available for $2,500 to $3,000.

It's good that you have that tach. Max rpms, plus a GPS to gauge your speed, are going to be your best metrics on performance of your specific hull/motor package. Sounds as if you're well-experienced to judge whether your motor is overpropped, in which case you'll need to try a different prop. Most here have tested from 3 to 6 props, looking to optimize their particular hulls with various outboards. Since the Mac26 can just barely plane at 15 knots with a 50hp, it seems totally unlikely (to me) that your 25 has any chance of reaching 13 knots.

[beene]

Read this...

http://macgregorsailors.com/phpBB/viewt ... hlight=rpm

G

[magnetic]

Hi Frank - I bought my 19 last week; at present there are 3 for sale in the UK, one has a 9.8hp, one another 25hp Yamaha, and I think the third has a Suzi 40. I take your point that these are rare beasts, and I have to confess that my heart is set on a 26M - but that will have to wait until next year.

The UK/USA price debate is a really curious one; the Bank exchange rate is around $2.00 = £1.00, but, in practice, everything over here from Big Macs to big engines is twice the price - and that includes the 26M.

Macgregor have cottoned on to this and, if you buy a boat stateside and try to export it, they will invalidate your warranty. Similarly, with outboards, not only do we have lumpy shipping charges to consider, but also import duties even on secondhand goods. In short, we just have to pony up the extra cost!

The 25hp Yamaha on the boat seems to be in good condition and instinctively it sounds "right"; it just pushes the nose into the clouds around 7mph and has simply no ideas about planing. I may stick some old Dolefins I have on it next week and see what happens. maybe nothing, but at least my garage will look a little tidier without them kicking around in the "Really Useful - Don't Throw It Away" pile.

In closing - and to apologise for my frustration - I think this forum (and the support for Mac boats in general) is fantastic; that having been said, I have noticed a certain degree of disdain for the 19, and a general obsession with engine size as the solution to all dreams and problems. If size were an issue, I wouldn't have bought a 19 !

Back on planet earth, having just shelled out $18,000 for a boat that I don't yet know how to sail, my appetite for ponying up a further $5,000 for an engine I may perhaps not need is slightly muted just now. Maybe that will change ; in the meantime I remain an experienced powerboater, albeit without a powerboat ......

N.B. I have just contacted the Guinness Book of World Records and am now looking for volunteers for an attempt on the record for getting the most adults into the heads compartment in a Mac 19. My best effort so far was 0.5 people all at the same time, and that only worked because he was absolutely bursting to use the pot

All the best - an otherwise very contended owner

[magnetic]

Many thanks for that link to Alex's posting - it seems he had the same problem as me!

I've just been outside in the dark and the rain, and although the prop is not marked, I measure it at around about 10 inches and an indeterminate pitch. I'd better get out there with the Tiny Tach next weekend!

Based on Alex's experimentation it seems that planing speeds might just be achievable with a 25hp, providing that I de-pitch a bit. On this point Alex notes that, although he can get higher revs with an 8 inch pitch, he gets a lower overall speed through the water due to cavitation.

Would either a wider prop (i.e. 12 x 8 inches ) help, or the addition of a hydrofoil? I anticipate that a pair of Dolefins might lift it up a bit, but would they perhaps also address the cavitation problems too?

This forum is phenomenally useful - my sincere thanks to all of you, even those died-in-the-wool petrolheads who are hooked on cubic inches as the solution to all the worlds problems. (Believe me, I'd go down that route too if I could afford to!)

[beene]

Read this... specifically posts by Highlander in this thread

http://macgregorsailors.com/phpBB/viewt ... &&start=15

G

[Duane Dunn, Allegro]

I you do end up buying a new motor and an M is in your future, I would buy a 50hp. Put it on the 19, store the 25. When it comes time to move up swap the motors back and sell the 19 with the 25, then put the 50 in the garage on the new M. At least then you will get longer term use out of your motor dollars.

Of course many are using bigger motors on their M's now but they might be more picky about the factory recommended size as part of the CE certification. Can you go bigger than a 50 on a M over there?

[Chip Hindes]

I have no knowledge of the Mac 19, but I know a 26X with a 9.9HP will do six knots.

If you can't do better than that on your Mac19 with 25HP, there is something wrong with your motor, prop, or speedometer.

[Deeseas]

I have a Mac 19 with a 40 H.P. Tohatsu so I don't know what a 25 H.P. can or can't do, but I also run a 5 H.P kicker for fishing and it will do 6 mph @ WOT with me, the wife and 200 lbs. of gear. Weight distribution is key when powering, if the wife sits below on the edge of the v-berth the boat will gain 2 mph over when she sits across from me in the cockpit at WOT. As for your sink drain question run a short hose from the drain to a small 1 or 2 gal. water bag. And finally the answer is yes everyone is jealous of the Mac 19

[johnnyonspot]

I have no knowledge of the Mac 19, but I know a 26X with a 9.9HP will do six knots.

If you can't do better than that on your Mac19 with 25HP, there is something wrong with your motor, prop, or speedometer.

Indeed. I was running 6.5 knots yesterday in my Mac 25 with 9.9 Mariner going wide open.