Anyone here have advice on what motor I should get to use with a Reynolds 21? I seem to remember reading that a 5 hp was recommended, but can't remember where and that was probably based on a (lighter) 2 cycle engine. Long shaft? Extra long shaft? I will likely have to do a fair bit of motoring (I'm a ways from open water) and will probably have to settle for a 4 cycle (good, 2 cycles are as rare as hens teeth).

I had a 3.5 Merc two stroke on mine, long shaft. Pushed it fine in flat water, was marginal at controlling the boat in a blow. Was hard to keep it in the water in a big chop. More power would be nice, but added weight is unwelcome. Tohatsu makes a 4 hp four stroke with an integral tank (and optional feed for a separate tank) that may be the lightest four stroke of that power. Most of the fives seem noticeably heavier. My boat had a fixed motor mount. I've since then constructed ones that can pivot up when not powering, which both allows the lower unit to be immersed a bit more when down, and then pulled up to nearly horizontal at rest.

@davefarmer - Any chance you can post a photo or two of your motor mount? According to the manufacturer's specs, the Suzuki is a few pounds lighter but they also offer an "extra long" shaft model (25" shaft) that weighs 60 lbs. I'm still hoping to find a 2 cycle but finding a good 2 cycle long shaft that's in good condition isn't easy.

I crewed on a Reynolds 21 for years and currently own a Stiletto 27. I have seen a dozen different motors on these boats. If you can find one I think you would be very happy with the OMC series of motors made from the late 1970's until 1991 that comes in a variety of horsepower options from 6hp to 9hp that were marketed as the Yachtwin or Sailmaster models. They are all long shaft, light (60lbs or so), with high thrust prop and have a 12v lead to power up house batteries.

However, as you pointed out, very hard to find especially in good condition. I picked one up recently in very good condition for 500$ but had to drive 6 hours round trip to get it after 3-4 months of looking in craigslist several times a week.

I think high thrust prop is the key to making it work well. If it has a "high speed" prop you will cavitate a lot.

Good luck on your search.

Brad



Edited by bradinjax on Apr 24, 2018 - 09:36 AM.

i have no advice on what engine to get but i have some info that may be useful or at least interesting

I have crewed on my friends F31R several times - I have helmed it under sail, under motor (sans sails pulling out of the ramp/ and also motor-sailing it under a bridge

He has a 7hp Nissan on his tri
it is fine downwind but will max out around 7knots (sans sails) - so if you are in a 8 knot current going against the flow - you "aint going"

He told me regardless of HP these boats will only go so fast under motor - so getting a "bigger engine" (more hp) isn't gonna help, only add weight

best of luck - let see some pics :)

MN3

...He told me regardless of HP these boats will only go so fast under motor - so getting a "bigger engine" (more hp) isn't gonna help, only add weight...

Yup, he's talking about a boat's "hull speed" which is determined by its waterline length. This boat has a 20 foot waterline so hull speed is roughly 6 knots. Unless you can get it up on a plane it won't go any faster than 6 knots.

I already have a 4 cycle 4 HP Tohatsu short shaft outboard that I'm pretty sure won't be deep enough, so I'm probably going to look for a 6 HP with either a long shaft or extra long shaft.



Edited by gobigkahuna on Apr 24, 2018 - 02:52 PM.

Those Tohatsu motors are interesting, I used a 6hp one a while back, and looked into the whole line. The 4, 5, and 6 hp variants are single piston 123cc motors with the same bore & stroke... they run in different RPM ranges with different props. All have short and long leg variants -- the 6 has an even extra-long option.
https://onlineoutboards.c…s/tohatsu-4-hp-outboards
https://onlineoutboards.c…s/tohatsu-5-hp-outboards
https://onlineoutboards.c…s/tohatsu-6-hp-outboards
(No affiliation with these guys, just easy quick data.)
The major difference seems to be the carburetor and the prop, both of which go to RPM range... and cost. You can always run the bigger motor at lower RPM, though efficiency may suffer slightly. Talk to an outboard repair guy, the difference may be jets or even a simple restrictor plate!

Nissan and Tohatsu appear to source from the same place. The paint job, documentation, and warranty may differ...

Randii

Yup hull speed and no way these little motors are getting these tris on a plane
I think the tohatsu is the same engine as the Nissan may have some different part’s but basically the same


I own a tohatsu 3.5 and it’s great



Edited by MN3 on Apr 24, 2018 - 03:18 PM.

When I bought my 4 HP Tohatsu I was told that it was identical to the 6 HP, the only difference was the carburetor. I never tried to swap carbs so I can't say for sure if that info was true or not.

I've owned several different outboards over the years and haven't had any issues with any of them. But I typically take pretty good care of my toys so that could be part of the reason. ;)

randii

Those Tohatsu motors are interesting, I used a 6hp one a while back, and looked into the whole line. The 4, 5, and 6 hp variants are single piston 123cc motors with the same bore & stroke... they run in different RPM ranges with different props. All have short and long leg variants -- the 6 has an even extra-long option.
https://onlineoutboards.c…s/tohatsu-4-hp-outboards
https://onlineoutboards.c…s/tohatsu-5-hp-outboards
https://onlineoutboards.c…s/tohatsu-6-hp-outboards
(No affiliation with these guys, just easy quick data.)
The major difference seems to be the carburetor and the prop, both of which go to RPM range... and cost. You can always run the bigger motor at lower RPM, though efficiency may suffer slightly. Talk to an outboard repair guy, the difference may be jets or even a simple restrictor plate!

Nissan and Tohatsu appear to source from the same place. The paint job, documentation, and warranty may differ...

Randii

I have used both the 4hp Nissan and 6hp Tohatsu 1 cylinder motors and both vibrated a lot. The Tohatsu vibrated so much the co-pilot adjustment would not keep it aligned. No matter how much you tightened it within 15-20 mins the motor torque and vibration would slowly turn the motor. It was virtually impossible to maintain a straight course for any length of time at high RPM.

gobigkahuna

MN3

...He told me regardless of HP these boats will only go so fast under motor - so getting a "bigger engine" (more hp) isn't gonna help, only add weight...

Yup, he's talking about a boat's "hull speed" which is determined by its waterline length. This boat has a 20 foot waterline so hull speed is roughly 6 knots. Unless you can get it up on a plane it won't go any faster than 6 knots.

I already have a 4 cycle 4 HP Tohatsu short shaft outboard that I'm pretty sure won't be deep enough, so I'm probably going to look for a 6 HP with either a long shaft or extra long shaft.Edited by gobigkahuna on Apr 24, 2018 - 02:52 PM.

I have found the hull speed formula:

hull speed in knots equals 1.34 times the square root of the waterline

only works well for monohulls, somewhat for tri's and is completely irrelevant for catamarans. The Reynolds 21 I crewed on in Miami used a 15hp high thrust Yamaha 2 cycle outboard to go to the Bahamas regularly as a charter boat and would motor at 3/4 throttle at 11-12mph. Full throttle was 15mph but used 2x fuel.

bradinjax

...The Reynolds 21 I crewed on in Miami used a 15hp high thrust Yamaha 2 cycle outboard to go to the Bahamas regularly as a charter boat and would motor at 3/4 throttle at 11-12mph. Full throttle was 15mph but used 2x fuel.

That's really interesting. My last 2 cycle 15 hp outboard weighed about 75 lbs, so I'm guessing your Yamaha was probably about the same. Any issues with so much weight that far aft? That's a really small boat for that sort of trip (especially with paying passengers). How well did it handle the open sea?

my pal uses a nissan 7hp (4 stroke i think) on his 31' tri
his max speed is 7 knots (so he claims)

so that works pretty well with your equation

1.34 x the square root of 31 = 7.46080424619

side note: this formula fails on my jonboat :)



Edited by MN3 on Apr 24, 2018 - 06:10 PM.

These are some pics posted in the technical photo section. The important feature is that the arm is hinged at the beam bracket, which allows the arm and motor to be pulled upwards, getting the motor farther above the water. It can be held in this position with a pin inserted under the arm in the upper position, or I usually just have a wooden wedge (with a small tether line) that slides into the beam bracket channel, under the arm, and the weight of the pivoting assembly holds it in place. To lower, just pull up on the motor slightly and pull the wedge out.

On some boats, I've used 4 large s.s. hose clamps to attach the beam bracket to the beam, so I didn't need to drill into the rear beam. This only works when you can get the clamps under the traveller somehow.

https://www.thebeachcats.com/pictures?g2_itemId=112360&g2_GALLERYSID=433a2f8795ca09d4162c8d177e91d2b6



Edited by davefarmer on Apr 25, 2018 - 08:45 AM.

gobigkahuna

bradinjax

...The Reynolds 21 I crewed on in Miami used a 15hp high thrust Yamaha 2 cycle outboard to go to the Bahamas regularly as a charter boat and would motor at 3/4 throttle at 11-12mph. Full throttle was 15mph but used 2x fuel.

That's really interesting. My last 2 cycle 15 hp outboard weighed about 75 lbs, so I'm guessing your Yamaha was probably about the same. Any issues with so much weight that far aft? That's a really small boat for that sort of trip (especially with paying passengers). How well did it handle the open sea?

The Reynolds was home ported in Nassau and went back and forth to Miami for maintenance and off-season with no passengers. Typical crossing took 10 hours or so to Bimini and then another full day to Nassau. We liked to leave around midnight to cross the gulf stream at night for the good water and would usually get to port before lunch. Picking a good weather window is the key.

The Reynolds is a pretty wet boat without much freeboard. In swells over 2' your definitely going to get wet. I would not try 4' plus in it. It handled open ocean ok, it just was not very comfortable. I would describe it as a light coastal daysailer at best. It did not sail well with a lot of people on it. I would guess maximum is 6 adults for decent sailing.

It was a little squatty with the Yamaha 15 on it as well as 9gal fuel tank but we offset it with 2 large anchors, 20' of rode and 100' line as far forward in each hull as we could get them. After that it was pretty balanced.

I came to really like the way the daggerboards were angled. They actually provide lift. you can really feel it over 10mph.



Edited by bradinjax on Apr 25, 2018 - 06:31 PM.