tophat engine sizes

[Sailtime]

Hi all, I'm wondering what size hp diesel engines most people have in their Top Hats?
Currently I have a single cylinder 14hp Sole but may have access to a newer yanmar.. wondering what's common out there..

Cheers
Shea

[Phillip]

Shea,

About 10 hp is common and all you need but there is one Top Hat with a 20 hp ??

Doesn't go that much faster as hull speed is about 6 and a quarter knots.

What are you thinking of installing.

[Sailtime]

cool

yanmar 1gm10
thanks

[RodM]

A single cylinder motor will vary from 5-10hp, maybe stretch to 12. The Sole Mini 14 is 2 cylinder. I had a 5hp Volvo that pushed Pelagian along well. The Yanmar is a good motor. Check to make sure it's a 1GM10 as the earlier 1GM that looked the same but was 8hp. It should have 1GM10 stamped on the head. I picked up a 1GM for parts, the head was rusted out making rebuild very costly. The 1GM series can also have problems with coolant back flow into the cylinder if they get pin holes in the exhaust elbow, but by and large they're a great motor. I put one in my Vega (27ft) and it did a great job.

Cheers, Rod

[Sailtime]

Cheers Rod, I'm sure my Sole is a single cylinder! (says so in the manual..) it still runs well so I'll probably leave it as is.. I was being swayed by the thought of upgrading although on review.. if it aint broke..

[Troppo]

Hi Shea

Now you have me intrigued. Is your motor a Sole Mini 3? The extract of the manual you show says the Mini 3 is 12 HP. So your motor being 14 HP I am thinking it is something else.

Single cylinder motors are typically more noisy and vibrate more than 2 or more cylinders. However, if your motor is working and reliable, I encourage you to use it as long as possible before replacing. To replace a motor, it is not just the cost of the motor that will send you broke. From what I have read, the installation can cost just as much as a new motor, so final cost is double the cost of a new motor. Takes a bit of work to get the drive shaft aligned properly. Also, the engine bed may need altering.

With the amount of HP, once you reach hull speed you can pour on the horses and not go faster. Extra HP does not make the boat go faster (not a planing hull like a dinghy). The extra HP above pushing the hull to its physical top speed can come in useful when forces are trying to slow the boat down like when pushing against waves, against wind, towing a dinghy or another boat. On flat calm water with a clean hull and not towing anything, I think you could do hull speed with maybe 5 or 6 hp (at a guess from what others have said). So, a Top Hat with a 14 hp motor may never need to fully rev up. Certainly won't be quickly wearing the motor out but running a diesel too slowly for too long apparently is not good.

So, the size of your motor at 14 hp is well and truly big enough for general cruising and plenty in reserve if you have to punch against strong winds and waves. Reliability is another issue. Generally if a diesel is serviced regularly (clean oil, clean filters, clean fuel) then it lasts a lifetime.

troppo

[Sailtime]

I'm sure it's a MINI 3.. looks just like the picture (slightly more oily) and yep I guess it's 12hp

I never have to rev it up past 1000rpm.. maybe i should occasionally..

cheers
shea

[Troppo]

I think 12 hp is a good size for a Top Hat. Plenty of reserve.

I am no expert but I think it worthwhile to run the motor a bit harder sometimes.

I am not even going to suggest that if your diesel motor fails you get a petrol outboard.

troppo